Self-affirmation alters the brain’s response to health messages and subsequent behavior change

Health communications can be an effective way to increase positive health behaviors and decrease negative health behaviors; however, those at highest risk are often most defensive and least open to such messages. For example, increasing physical activity among sedentary individuals affects a wide range of important mental and physical health outcomes, but has proven a challenging task. Affirming core values (i.e., self-affirmation) before message exposure is a psychological technique that can increase the effectiveness of a wide range of interventions in health and other domains; however, the neural mechanisms of affirmation’s effects have not been studied. We used functional magnetic resonance imaging (fMRI) to examine neural processes associated with affirmation effects during exposure to potentially threatening health messages. We focused on an a priori defined region of interest (ROI) in ventromedial prefrontal cortex (VMPFC), a brain region selected for its association with self-related processing and positive valuation. Consistent with our hypotheses, those in the self-affirmation condition produced more activity in VMPFC during exposure to health messages and went on to increase their objectively measured activity levels more. These findings suggest that affirmation of core values may exert its effects by allowing at-risk individuals to see the self-relevance and value in otherwise-threatening messages.Promoting physical activity and decreasing sedentary behavior are major strategies to manage and prevent chronic diseases (1–16). In particular, sedentary behavior increases risk, independent of other types of activity, and exchanging sedentary for even light activity has physiological and psychological benefits (17–23). However, sedentary lifestyle is still prevalent despite worldwide efforts to increase activity; according to the World Health Organization, “60% to 85% of people in the world—from both developed and developing countries—lead sedentary lifestyles” (24). Thus, effective, theory-driven behavior change interventions are critical (25, 26).One major difficulty in decreasing sedentary and other health risk behaviors through health communication tools is that self-relevant health messages can be perceived to be threatening to self-worth and are often met with resistance. This phenomenon speaks to a classic and problematic paradox: those at highest risk are likely to be defensive, reducing openness to altering risk behaviors (27).     

Rapid upslope shifts in New Guinean birds illustrate strong distributional responses of tropical montane species to global warming

Temperate-zone species have responded to warming temperatures by shifting their distributions poleward and upslope. Thermal tolerance data suggests that tropical species may respond to warming temperatures even more strongly than temperate-zone species, but this prediction has yet to be tested. We addressed this data gap by conducting resurveys to measure distributional responses to temperature increases in the elevational limits of the avifaunas of two geographically and faunally independent New Guinean mountains, Mt. Karimui and Karkar Island, 47 and 44 y after they were originally surveyed. Although species richness is roughly five times greater on mainland Mt. Karimui than oceanic Karkar Island, distributional shifts at both sites were similar: upslope shifts averaged 113 m (Mt. Karimui) and 152 m (Karkar Island) for upper limits and 95 m (Mt. Karimui) and 123 m (Karkar Island) for lower limits. We incorporated these results into a metaanalysis to compare distributional responses of tropical species with those of temperate-zone species, finding that average upslope shifts in tropical montane species match local temperature increases significantly more closely than in temperate-zone montane species. That tropical species appear to be strong responders has global conservation implications and provides empirical support to hitherto untested models that predict widespread extinctions in upper-elevation tropical endemics with small ranges.Temperate species are responding to anthropogenic temperature increases by rapidly shifting geographic distributions to track their climatic niche (1–3). These shifts appear to be increasing in pace—a recent metaanalysis concluded that species are shifting their distributions poleward and upslope much faster than previously estimated (1, 2). Range shifts are less studied in tropical regions however (1, 4, 5), despite being home to the vast majority of biodiversity (6). Notwithstanding strong latitudinal bias in empirical studies, climate change-driven range shifts are predicted to cause widespread extinctions in both temperate and tropical species within the next century (7–10).With scarce empirical data, models of tropical species’ response to temperature increases predict a wide range of responses (11). At one extreme, tropical species may be relatively unaffected, as the magnitude of temperature increases is relatively low in the tropics (12). Alternately, vulnerability to warming temperatures could be highest in the tropics if tropical species are physiologically specialized to narrow thermal niches (13–18). Such thermal specialization has been documented in tropical ectotherms (16, 17), but it is unclear whether similar patterns may apply to tropical endotherms, whose distributional shifts in response to warming may result from indirect rather than direct impacts of temperature increases (5).We resurveyed geographically and faunally independent elevational gradients in New Guinea nearly a half-century after they were first surveyed. The original transect surveys were conducted by J. Diamond to determine bird species’ elevational limits on Mt. Karimui (July–August 1965) (19) and Karkar Island (May 1969) (20). These environments differ significantly: Mt. Karimui is located in New Guinea’s biodiverse Central Ranges and harbors a diverse resident avifauna of ca. 250 resident landbirds (19), whereas Karkar Island is a small oceanic island off New Guinea’s north coast with a depauperate flora and fauna (ca. 50 resident landbirds) dominated by highly dispersive taxa (20) (Fig. 1).Open in a separate windowFig. 1.Map of resurvey sites in Papua New Guinea. The elevational transects recently revisited by the authors are marked by dashed lines (Mt. Karimui: 1,130–2,520 m; Karkar Island: 800–1,600 m). Mt. Karimui is an extinct volcano in the southern Central Ranges of New Guinea, whereas Karkar Island is an oceanic island located 10 miles from the New Guinean mainland. These elevational gradients were originally surveyed by Diamond in the 1960s [Mt. Karimui: 1965 (19); Karkar Island: 1969 (20)], and remain covered in primary forest.We used elevational limits measured during historical transects and modern resurveys to investigate New Guinean montane birds’ response to warming temperatures. We predicted that species have moved upslope relative to historical range limits. Given that tropical species are hypothesized to be especially sensitive to temperature increases (either directly or via indirect ecological interactions), we additionally predicted that the magnitude of upslope shifts would closely match predicted shifts based on local temperature increases. We simultaneously tested two additional hypotheses, investigating whether upslope shifts at the leading range margin outpaced upslope shifts at the trailing range edge (21), and whether species’ dietary preferences influenced upslope shifts (22, 23). We then used our data in conjunction with recent tropical resurveys to test the tropical-species-are-strong-responders hypothesis, predicting that upslope shifts measured in tropical resurveys match predicted upslope shifts significantly more closely than for temperate-zone resurveys.     

Drosophila seminal protein ovulin mediates ovulation through female octopamine neuronal signaling

Across animal taxa, seminal proteins are important regulators of female reproductive physiology and behavior. However, little is understood about the physiological or molecular mechanisms by which seminal proteins effect these changes. To investigate this topic, we studied the increase in Drosophila melanogaster ovulation behavior induced by mating. Ovulation requires octopamine (OA) signaling from the central nervous system to coordinate an egg’s release from the ovary and its passage into the oviduct. The seminal protein ovulin increases ovulation rates after mating. We tested whether ovulin acts through OA to increase ovulation behavior. Increasing OA neuronal excitability compensated for a lack of ovulin received during mating. Moreover, we identified a mating-dependent relaxation of oviduct musculature, for which ovulin is a necessary and sufficient male contribution. We report further that oviduct muscle relaxation can be induced by activating OA neurons, requires normal metabolic production of OA, and reflects ovulin’s increasing of OA neuronal signaling. Finally, we showed that as a result of ovulin exposure, there is subsequent growth of OA synaptic sites at the oviduct, demonstrating that seminal proteins can contribute to synaptic plasticity. Together, these results demonstrate that ovulin increases ovulation through OA neuronal signaling and, by extension, that seminal proteins can alter reproductive physiology by modulating known female pathways regulating reproduction.Throughout internally fertilizing animals, seminal proteins play important roles in regulating female fertility by altering female physiology and, in some cases, behavior after mating (reviewed in refs. 1–3). Despite this, little is understood about the physiological mechanisms by which seminal proteins induce postmating changes and how their actions are linked with known networks regulating female reproductive physiology.In Drosophila melanogaster, the suite of seminal proteins has been identified, as have many seminal protein-dependent postmating responses, including changes in egg production and laying, remating behavior, locomotion, feeding, and in ovulation rate (reviewed in refs. 2 and 3). For example, the Drosophila seminal protein ovulin elevates ovulation rate to maximal levels during the 24 h following mating (4, 5), and the seminal protein sex peptide (SP) suppresses female mating receptivity and increases egg-laying behavior for several days after mating (6–10). However, although a receptor for SP has been identified (11), along with elements of the neural circuit in which it is required (12–14), SP’s mechanism of action has not yet been linked to regulatory networks known to control postmating behaviors. Thus, a crucial question remains: how do male-derived seminal proteins interact with regulatory networks in females to trigger postmating responses?We addressed this question by examining the stimulation of Drosophila ovulation by the seminal protein ovulin. In insects, ovulation, defined here as the release of an egg from the ovary to the uterus, is among the best understood reproductive processes in terms of its physiology and neurogenetics (15–27). In D. melanogaster, ovulation requires input from neurons in the abdominal ganglia that release the catecholaminergic neuromodulators octopamine (OA) and tyramine (17, 18, 28). Drosophila ovulation also requires an OA receptor, OA receptor in mushroom bodies (OAMB) (19, 20). Moreover, it has been proposed that OA may integrate extrinsic factors to regulate ovulation rates (17). Noradrenaline, the vertebrate structural and functional equivalent to OA (29, 30), is important for mammalian ovulation, and its dysregulation has been associated with ovulation disorders (31–38). In this paper we investigate the role of neurons that release OA and tyramine in ovulin’s action. For simplicity, we refer to these neurons as “OA neurons” to reflect the well-established role of OA in ovulation behavior (16–20, 22).We investigated how action of the seminal protein ovulin relates to the conserved canonical neuromodulatory pathway that regulates ovulation physiology (39–41). We found that ovulin increases ovulation and egg laying through OA neuronal signaling. We also found that ovulin relaxes oviduct muscle tonus, a postmating process that is also mediated by OA neuronal signaling. Finally, subsequent to these effects we detected an ovulin-dependent increase in synaptic sites between OA motor neurons and oviduct muscle, suggesting that ovulin’s stimulation of OA neurons could have increased their synaptic activity. These results suggest that ovulin affects ovulation by manipulating the gain of a neuromodulatory pathway regulating ovulation physiology.     

From the Cover: Intergenerational transmission of emotional trauma through amygdala-dependent mother-to-infant transfer of specific fear

Emotional trauma is transmitted across generations. For example, children witnessing their parent expressing fear to specific sounds or images begin to express fear to those cues. Within normal range, this is adaptive, although pathological fear, such as occurs in posttraumatic stress disorder or specific phobias, is also socially transmitted to children and is thus of clinical concern. Here, using a rodent model, we report a mother-to-infant transfer of fear to a novel peppermint odor, which is dependent on the mother expressing fear to that smell in pups’ presence. Examination of pups’ neural activity using c-Fos early gene expression and ¹⁴C 2-deoxyglucose autoradiography during mother-to-infant fear transmission revealed lateral and basal amygdala nuclei activity, with a causal role highlighted by pharmacological inactivation of pups’ amygdala preventing the fear transmission. Maternal presence was not needed for fear transmission, because an elevation of pups’ corticosterone induced by the odor of the frightened mother along with a novel peppermint odor was sufficient to produce pups’ subsequent aversion to that odor. Disruption of axonal tracts from the Grueneberg ganglion, a structure implicated in alarm chemosignaling, or blockade of pups’ alarm odor-induced corticosterone increase prevented transfer of fear. These memories are acquired at younger ages compared with amygdala-dependent odor-shock conditioning and are more enduring following minimal conditioning. Our results provide clues to understanding transmission of specific fears across generations and its dependence upon maternal induction of pups’ stress response paired with the cue to induce amygdala-dependent learning plasticity. Results are discussed within the context of caregiver emotional responses and adaptive vs. pathological fears social transmission.Children, including infants, use their parents’ emotions to guide their behavior and learn about safety and danger (1–4). The infant’s ability to regulate behavior in novel situations using the caregiver’s emotional expression is known as social referencing and occurs in humans and nonhuman primates (1). Although parental physical presence itself or particular cues indicating parental presence, such as voice, touch, or smell typically signal safety for the child, infants are especially responsive to the caregiver’s communication during threats (3–5). This social learning is critical for enhancing survival through an adaptation to the environment but also provides transmission of pathological fears, such as occurs in posttraumatic stress disorder (PTSD) or in specific phobias (3–7).Despite existing evidence that children are sensitive to parental fear and anxiety, the neurobiological mechanisms for the transmission of parental specific fear to the offspring have remained elusive (2–7). Animal studies investigating the impact of parental stress on the offspring focused on the history of parental trauma, quality of maternal care, and resultant overall behavioral alterations in the offspring (7, 8). However, to develop efficient survival strategies, progenies must learn about specific environmental threats triggering parental fear (9).Most of what we know about fear learning comes from studies using fear conditioning (FC) (10). In FC, a neutral sensory cue [conditioned stimulus (CS)] is paired with a noxious event [unconditioned stimulus (US)]. Animal studies indicate that the amygdala’s lateral and basal nuclei (LBA) play an important role in FC (10). However, FC in infant rats is naturally attenuated until postnatal day (PND) 10 due to low levels of the stress hormone corticosterone (CORT) during the stress hyporesponsive period (11–15). This fear suppression continues in older pups (until PND 16) in the mother’s presence due to social buffering (attenuation) of the shock-induced CORT increase (15).To study the intergenerational transmission of fear to specific triggers, we developed a mother-to-infant social fear learning paradigm. In social fear learning, an organism learns fear through an exposure to a conspecific expressing fear to a discrete CS. Social fear learning may thus serve as a model explaining how defense responses to specific triggers are transmitted between individuals. Social fear learning has been demonstrated in primates, including humans and in rodents, and involves the amygdala (16–19).     

Collapse of cooperation in evolving games

Game theory provides a quantitative framework for analyzing the behavior of rational agents. The Iterated Prisoner’s Dilemma in particular has become a standard model for studying cooperation and cheating, with cooperation often emerging as a robust outcome in evolving populations. Here we extend evolutionary game theory by allowing players’ payoffs as well as their strategies to evolve in response to selection on heritable mutations. In nature, many organisms engage in mutually beneficial interactions and individuals may seek to change the ratio of risk to reward for cooperation by altering the resources they commit to cooperative interactions. To study this, we construct a general framework for the coevolution of strategies and payoffs in arbitrary iterated games. We show that, when there is a tradeoff between the benefits and costs of cooperation, coevolution often leads to a dramatic loss of cooperation in the Iterated Prisoner’s Dilemma. The collapse of cooperation is so extreme that the average payoff in a population can decline even as the potential reward for mutual cooperation increases. Depending upon the form of tradeoffs, evolution may even move away from the Iterated Prisoner’s Dilemma game altogether. Our work offers a new perspective on the Prisoner’s Dilemma and its predictions for cooperation in natural populations; and it provides a general framework to understand the coevolution of strategies and payoffs in iterated interactions.Iterated games provide a framework for studying social interactions (1–6) that allows researchers to address pervasive biological problems such as the evolution of cooperation and cheating (2, 7–12). Simple examples such as the Iterated Prisoner’s Dilemma, Snowdrift, and Stag Hunt games (13–18) showcase a startling array of counterintuitive social behaviors, especially when studied in a population replicating under natural selection (16, 19–25). Despite the subject’s long history, a systematic treatment of all evolutionary robust cooperative outcomes for even the simple Iterated Prisoner’s Dilemma has only recently emerged (21, 26–29).Understanding the evolution of strategies in a population under fixed payoffs already poses a steep challenge. To complicate matters further, in many biological settings the payoffs themselves may also depend on the genotypes of the players. Changes to the payoff matrix have been studied in a number of contexts, including one-shot two-player games (13), payoff evolution without strategy evolution (30, 31), under environmental “shocks” to the payoff matrix (32–34), and using continuous games (22, 23, 35). Here we adopt a different approach, and we explicitly study the coevolutionary dynamics between strategies and payoffs in iterated two-player games. We decouple strategy mutations from payoff mutations, and we leverage results on the evolutionary robustness of memory-1 strategies with arbitrary payoff matrices to explore the relationship between payoff evolution and the prevalence of cooperation in a population. We identify a feedback between the costs and benefits of cooperation and the evolutionary robustness of cooperative strategies. Depending on the functional form (35) of the relationship between costs and benefits, this feedback may either reinforce the evolutionary success of cooperation or else precipitate its collapse. In particular, we show that cooperation will always collapse when there are diminishing returns for mutual cooperation.     

Heat of supersaturation-limited amyloid burst directly monitored by isothermal titration calorimetry

Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. Although the structural features of amyloid fibrils have become increasingly clearer, knowledge on the thermodynamics of fibrillation is limited. Furthermore, protein aggregation is not a target of calorimetry, one of the most powerful approaches used to study proteins. Here, with β₂-microglobulin, a protein responsible for dialysis-related amyloidosis, we show direct heat measurements of the formation of amyloid fibrils using isothermal titration calorimetry (ITC). The spontaneous fibrillation after a lag phase was accompanied by exothermic heat. The thermodynamic parameters of fibrillation obtained under various protein concentrations and temperatures were consistent with the main-chain dominated structural model of fibrils, in which overall packing was less than that of the native structures. We also characterized the thermodynamics of amorphous aggregation, enabling the comparison of protein folding, amyloid fibrillation, and amorphous aggregation. These results indicate that ITC will become a promising approach for clarifying comprehensively the thermodynamics of protein folding and misfolding.Aggregation has often been an obstacle to studying the structure, function, and physical properties of proteins. However, a large number of aggregates associated with serious diseases, including Alzheimer’s, Parkinson, and prion diseases (1, 2) promoted the challenge of studying protein misfolding and aggregation. Researchers succeeded in distinguishing amyloid fibrils and oligomers from other amorphous aggregates and characterized the ordered structures present in amyloid fibrils or oligomers, which led to the development of the field of amyloid structural biology (3–8). These advances have been attributed to various methodologies that are also useful for studying the structural properties of globular proteins. Even X-ray crystallography has become a powerful approach for studying amyloid microcrystals (5) or oligomers (9). The atomic details of amyloid fibrils are becoming increasingly clearer, and a cross-β structure was shown to be the main structural component of fibrils (5, 6, 8). Although tightly packed core regions of amyloid fibrils have been reported, the overall structures were shown to be dominated by common cross-β structures, which supported the argument for the main-chain dominated architecture in contrast to the side-chain dominated architecture of globular native states (10–12).These structural studies have been complemented by a series of efforts to clarify the mechanism for the formation of amyloid fibrils (i.e., amyloid fibrillation). The presence of a long lag time in spontaneous fibrillation and rapid fibrillation by the addition of preformed fibrils represent a similarity with the supersaturation-limited crystallization of substances (13–18). We have revisited “supersaturation” and argued its critical role for amyloid fibrillation (17–19). The role of supersaturation in neurodegenerative diseases at the proteome level has been reported recently (20).However, calorimetry, one of the most powerful methods used to study the thermodynamic properties of globular proteins (21–24), has not played a significant role in understanding protein aggregation. The aggregation of proteins following heat denaturation as monitored by differential scanning calorimetry is an infamous example demonstrating how aggregation can prevent exact analyses (25, 26). To date, few studies have investigated protein aggregation including amyloid fibrils with calorimetry (27–32). Our previous study on the exothermic heat effects accompanying fibril growth was achieved by monitoring the seed-dependent elongation of fibrils formed by β₂-microglobulin (β2m), a protein responsible for dialysis-related amyloidosis, using isothermal titration calorimetry (ITC) (28).In the present study using β2m, we succeeded in characterizing the total heat of spontaneous fibrillation and amorphous aggregation. An analysis of the heat burst associated with fibrillation or amorphous aggregation under various temperatures clarified their thermodynamic properties. The results obtained enabled the calorimetric characterization of amyloid fibrils and amorphous aggregates relative to that of the native globular structures, which opens a new field for the calorimetric study of protein aggregates.     

Defining the rate-limiting processes of bacterial cytokinesis

Bacterial cytokinesis is accomplished by the essential ‘divisome’ machinery. The most widely conserved divisome component, FtsZ, is a tubulin homolog that polymerizes into the ‘FtsZ-ring’ (‘Z-ring’). Previous in vitro studies suggest that Z-ring contraction serves as a major constrictive force generator to limit the progression of cytokinesis. Here, we applied quantitative superresolution imaging to examine whether and how Z-ring contraction limits the rate of septum closure during cytokinesis in Escherichia coli cells. Surprisingly, septum closure rate was robust to substantial changes in all Z-ring properties proposed to be coupled to force generation: FtsZ’s GTPase activity, Z-ring density, and the timing of Z-ring assembly and disassembly. Instead, the rate was limited by the activity of an essential cell wall synthesis enzyme and further modulated by a physical divisome–chromosome coupling. These results challenge a Z-ring–centric view of bacterial cytokinesis and identify cell wall synthesis and chromosome segregation as limiting processes of cytokinesis.The mechanisms that drive bacterial cell division have been sought out for many decades because of their essential role in bacterial proliferation and their appeal as targets for new antibiotic development (1). Numerous cellular and biochemical investigations have revealed that bacterial cytokinesis is carried out by a dynamic, supramolecular complex termed the ‘divisome.’ The divisome assembles at midcell to coordinate constriction of the multilayer cell envelope (2), which involves both membrane invagination and new septal cell wall synthesis.Divisome assembly is initiated by the highly-conserved tubulin-like GTPase FtsZ (3, 4). FtsZ’s membrane tethers [FtsA and ZipA in Escherichia coli (5, 6)] promote FtsZ’s polymerization into a ring-like structure, or ‘FtsZ-ring’ (‘Z-ring’), at the cytoplasmic face of the inner membrane (7). Once established, the Z-ring recruits an ensemble of transmembrane and periplasmic proteins involved in cell wall peptidoglycan (PG) synthesis and remodeling, including the essential transpeptidase and penicillin-binding protein PBP3 (also called FtsI) (8, 9). Recently, a new group of Z-ring–associated proteins (Zaps) has been shown to stabilize the Z-ring (10–15). Some of these Zaps connect the Z-ring to the bacterial chromosome through a multilayered protein network that includes the chromosome-binding protein MatP (16–19). Together with FtsK, a divisome protein involved in chromosome segregation and dimer resolution (20–25), this group of proteins likely plays a role in coordinating cell envelope invagination with chromosome segregation (16, 18, 26). Thus, the divisome consists of three interacting components: the Z-ring, PG-linked proteins, and chromosome-linked proteins.Successful cell constriction requires a mechanical force to act against the internal turgor pressure. However, the divisome component responsible for generating such a force remains unclear (27). One possibility that has garnered much attention in the last decade is a ‘Z-ring–centric’ model in which the Z-ring is analogous to the contractile actomyosin ring in eukaryotic cells: the Z-ring is thought to actively pull the cytoplasmic membrane inward, and septal PG growth follows passively behind (28). Such a model predicts that Z-ring contraction limits the progression of septum closure and is distinct from a model in which new septal PG growth actively pushes from the outside of the cytoplasmic membrane (27). In this latter model, PG synthesis limits the rate of septum closure, and the Z-ring acts as a scaffold that passively follows the closing septum (29). Alternatively, Z-ring contraction and septal cell wall synthesis may work together to drive constriction; in which case, progression of septum closure would be regulated by both processes (27).A large number of studies support the Z-ring–centric force generation model. For example, purified, membrane-tethered FtsZ was shown to assemble into ring-like structures that deform and constrict liposome membranes (30–35). Mechanistically, it has been proposed that a constrictive force could be generated by the bending of FtsZ protofilaments because of their preferred curvature or GTP hydrolysis-induced conformation change (36–41), immediate reannealing of FtsZ protofilaments upon GTP hydrolysis-induced subunit loss (42), condensation of FtsZ protofilaments caused by their lateral affinity (43), or a combination of these mechanisms (38, 42, 44, 45). However, these proposed mechanisms have been difficult to test in vivo because of the essentiality of FtsZ, the limited ability to spatially resolve the Z-ring structure in small bacterial cells, and the lack of sensitive methods to monitor Z-ring contraction and the rate of septum closure.In this work, we applied quantitative superresolution imaging in combination with other biophysical techniques to characterize Z-ring structure and dynamics during constriction and to probe the rate of septum closure during cell constriction. We reasoned that perturbations to the structure or activity of the major force-generating divisome component should result in significant changes to the rate of septum closure, allowing us to identify possible molecular mechanisms for constriction force generation.Surprisingly, we found that the rate of septum closure was unaffected by many substantial alterations to the Z-ring, including FtsZ’s GTPase activity, molecular density of the Z-ring, and the timing of Z-ring assembly and disassembly. Instead, the rate of septum closure was proportional to the rate of cell elongation and was significantly reduced when FtsI activity was compromised, indicating that cell wall synthesis plays a limiting role in septum closure. Interestingly, we found that deletion of matP caused the septum to close faster than predicted by the corresponding cell elongation rate, indicating that the coordination of cell envelope invagination with chromosome segregation by MatP can influence the progression of cell constriction.Taken together, our results challenge the FtsZ-centric view of bacterial cytokinesis, highlight the role of septal cell wall growth and chromosome segregation in driving and modulating the rate of septum closure, and support a holistic view of constrictive force generation by the multicomponent divisome.     

From the Cover: Mother’s voice and heartbeat sounds elicit auditory plasticity in the human brain before full gestation

Brain development is largely shaped by early sensory experience. However, it is currently unknown whether, how early, and to what extent the newborn’s brain is shaped by exposure to maternal sounds when the brain is most sensitive to early life programming. The present study examined this question in 40 infants born extremely prematurely (between 25- and 32-wk gestation) in the first month of life. Newborns were randomized to receive auditory enrichment in the form of audio recordings of maternal sounds (including their mother’s voice and heartbeat) or routine exposure to hospital environmental noise. The groups were otherwise medically and demographically comparable. Cranial ultrasonography measurements were obtained at 30 ± 3 d of life. Results show that newborns exposed to maternal sounds had a significantly larger auditory cortex (AC) bilaterally compared with control newborns receiving standard care. The magnitude of the right and left AC thickness was significantly correlated with gestational age but not with the duration of sound exposure. Measurements of head circumference and the widths of the frontal horn (FH) and the corpus callosum (CC) were not significantly different between the two groups. This study provides evidence for experience-dependent plasticity in the primary AC before the brain has reached full-term maturation. Our results demonstrate that despite the immaturity of the auditory pathways, the AC is more adaptive to maternal sounds than environmental noise. Further studies are needed to better understand the neural processes underlying this early brain plasticity and its functional implications for future hearing and language development.One of the first acoustic stimuli we are exposed to before birth is the voice of the mother and the sounds of her heartbeat. As fetuses, we have substantial capacity for auditory learning and memory already in utero (1–5), and we are particularly tuned to acoustic cues from our mother (6–9). Previous research suggests that the innate preference for mother’s voice shapes the developmental trajectory of the brain (10, 11). Prenatal exposure to mother’s voice may therefore provide the brain with the auditory fitness necessary to process and store speech information immediately after birth (12, 13).There is evidence to suggest that prenatal exposure to the maternal voice and heartbeat sounds can pave the neural pathways in the brain for subsequent development of hearing and language skills (14). For example, the periodic perception of the low-frequency maternal heartbeat in the womb provides the fetus with an important rhythmic experience (15, 16) that likely establishes the neural basis for auditory entrainment and synchrony skills necessary for vocal, gestural, and gaze communication during mother–infant interactions (17, 18).Studies examining the neural response to the maternal voice soon after birth have found activation in posterior temporal regions, preferentially on the left side, as well as brain areas involved in emotional processing including the amygdala and orbito-frontal cortex (19). Similarly, Beauchemin et al. have found activation in language-related cortical regions when newborns listened to their mother’s voice, whereas a stranger’s voice seemed to activate more generic regions of the brain (20). In addition, Partanen et al. have shown that the neural response to maternal sounds depends on experience as full-term newborns react differentially to familiar vs. unfamiliar sounds they were exposed to as fetuses, suggesting correlation between the amount of prenatal exposure and brain activity (21). Taken together, the above studies suggest that the mother’s voice plays a special role in the early shaping of auditory and language areas of the brain.Numerous animal studies have shown that brain development relies on developmentally appropriate acoustic stimulation early in life (22–32). Auditory deprivation during critical periods can adversely affect brain maturation and lead to long-lasting neural despecialization in the auditory cortex (AC), whereas auditory enrichment in the early postnatal period can enhance neural sensitivity in the primary AC, as well as improve auditory recognition and discrimination abilities.Preterm infants are born during a critical period for auditory brain development. However, the maternal auditory nursery provided by the womb vanishes after a premature birth as the preterm newborn enters the neonatal intensive care unit (NICU). The abrupt transition of the fetus from the protected environment of the womb to the exposed environment of the hospital imposes significant challenges on the developing brain (33). These challenges have been associated with neuropathologic consequences, including reduction in regional brain volumes, white matter microstructural abnormalities, and poor cognitive and language outcomes in preterm compared with full-term newborns (34–41).Considering the acoustic gap between the NICU environment and the womb, it is not surprising that auditory brain development is compromised in preterm compared with full-term infants (42, 43). Numerous studies have suggested that the auditory environment available for preterm infants in the NICU may not be conducive for their neurodevelopment (44–47). These concerns are derived from the frequent reality that hospitalized preterm newborns are overexposed to loud, toxic, and unpredictable environmental noise generated by ventilators, infusion pumps, fans, telephones, pagers, monitors, and alarms (48–51), whereas at the same time they are also deprived of the low-frequency, patterned, and biologically familiar sounds of their mother’s voice and heartbeat, which they would otherwise be hearing in utero (33, 45). In addition, the hospital environment contains a significant amount of high-frequency electronic sounds (52, 53) that are less likely to be heard in the womb because of the sound attenuation provided by maternal tissues and fluid within the intrauterine cavity (54–56). Efforts to improve the hospital environment for preterm neonates have primarily focused on reducing hospital noise and maintaining a quiet environment. However, exposing medically fragile preterm newborns to low-frequency audio recordings of their mothers on a daily basis has been less acknowledged to be of necessity, and the extent to which such maternal sound exposure can influence brain maturation after an extremely premature birth has been a matter of much debate.The present study aimed to determine whether enriching the auditory environment for preterm newborns with authentic recordings of their mother’s voice and heartbeat sounds in the first month of life would result in structural alterations in the AC. The rationale driving this question lies in the fact that such enriched maternal sound stimulation would otherwise be present had the baby not been born prematurely.     

Self-assembly of alkynylplatinum(II) terpyridine amphiphiles into nanostructures via steric control and metal–metal interactions

A series of mono- and dinuclear alkynylplatinum(II) terpyridine complexes containing the hydrophilic oligo(para-phenylene ethynylene) with two 3,6,9-trioxadec-1-yloxy chains was designed and synthesized. The mononuclear alkynylplatinum(II) terpyridine complex was found to display a very strong tendency toward the formation of supramolecular structures. Interestingly, additional end-capping with another platinum(II) terpyridine moiety of various steric bulk at the terminal alkyne would lead to the formation of nanotubes or helical ribbons. These desirable nanostructures were found to be governed by the steric bulk on the platinum(II) terpyridine moieties, which modulates the directional metal−metal interactions and controls the formation of nanotubes or helical ribbons. Detailed analysis of temperature-dependent UV-visible absorption spectra of the nanostructured tubular aggregates also provided insights into the assembly mechanism and showed the role of metal−metal interactions in the cooperative supramolecular polymerization of the amphiphilic platinum(II) complexes.Square-planar d⁸ platinum(II) polypyridine complexes have long been known to exhibit intriguing spectroscopic and luminescence properties (1–54) as well as interesting solid-state polymorphism associated with metal−metal and π−π stacking interactions (1–14, 25). Earlier work by our group showed the first example, to our knowledge, of an alkynylplatinum(II) terpyridine system [Pt(tpy)(C ≡ CR)]⁺ that incorporates σ-donating and solubilizing alkynyl ligands together with the formation of Pt···Pt interactions to exhibit notable color changes and luminescence enhancements on solvent composition change (25) and polyelectrolyte addition (26). This approach has provided access to the alkynylplatinum(II) terpyridine and other related cyclometalated platinum(II) complexes, with functionalities that can self-assemble into metallogels (27–31), liquid crystals (32, 33), and other different molecular architectures, such as hairpin conformation (34), helices (35–38), nanostructures (39–45), and molecular tweezers (46, 47), as well as having a wide range of applications in molecular recognition (48–52), biomolecular labeling (48–52), and materials science (53, 54). Recently, metal-containing amphiphiles have also emerged as a building block for supramolecular architectures (42–44, 55–59). Their self-assembly has always been found to yield different molecular architectures with unprecedented complexity through the multiple noncovalent interactions on the introduction of external stimuli (42–44, 55–59).Helical architecture is one of the most exciting self-assembled morphologies because of the uniqueness for the functional and topological properties (60–69). Helical ribbons composed of amphiphiles, such as diacetylenic lipids, glutamates, and peptide-based amphiphiles, are often precursors for the growth of tubular structures on an increase in the width or the merging of the edges of ribbons (64, 65). Recently, the optimization of nanotube formation vs. helical nanostructures has aroused considerable interests and can be achieved through a fine interplay of the influence on the amphiphilic property of molecules (66), choice of counteranions (67, 68), or pH values of the media (69), which would govern the self-assembly of molecules into desirable aggregates of helical ribbons or nanotube scaffolds. However, a precise control of supramolecular morphology between helical ribbons and nanotubes remains challenging, particularly for the polycyclic aromatics in the field of molecular assembly (64–69). Oligo(para-phenylene ethynylene)s (OPEs) with solely π−π stacking interactions are well-recognized to self-assemble into supramolecular system of various nanostructures but rarely result in the formation of tubular scaffolds (70–73). In view of the rich photophysical properties of square-planar d⁸ platinum(II) systems and their propensity toward formation of directional Pt···Pt interactions in distinctive morphologies (27–31, 39–45), it is anticipated that such directional and noncovalent metal−metal interactions might be capable of directing or dictating molecular ordering and alignment to give desirable nanostructures of helical ribbons or nanotubes in a precise and controllable manner.Herein, we report the design and synthesis of mono- and dinuclear alkynylplatinum(II) terpyridine complexes containing hydrophilic OPEs with two 3,6,9-trioxadec-1-yloxy chains. The mononuclear alkynylplatinum(II) terpyridine complex with amphiphilic property is found to show a strong tendency toward the formation of supramolecular structures on diffusion of diethyl ether in dichloromethane or dimethyl sulfoxide (DMSO) solution. Interestingly, additional end-capping with another platinum(II) terpyridine moiety of various steric bulk at the terminal alkyne would result in nanotubes or helical ribbons in the self-assembly process. To the best of our knowledge, this finding represents the first example of the utilization of the steric bulk of the moieties, which modulates the formation of directional metal−metal interactions to precisely control the formation of nanotubes or helical ribbons in the self-assembly process. Application of the nucleation–elongation model into this assembly process by UV-visible (UV-vis) absorption spectroscopic studies has elucidated the nature of the molecular self-assembly, and more importantly, it has revealed the role of metal−metal interactions in the formation of these two types of nanostructures.     

Realized niche shift during a global biological invasion

Accurate forecasts of biological invasions are crucial for managing invasion risk but are hampered by niche shifts resulting from evolved environmental tolerances (fundamental niche shifts) or the presence of novel biotic and abiotic conditions in the invaded range (realized niche shifts). Distinguishing between these kinds of niche shifts is impossible with traditional, correlative approaches to invasion forecasts, which exclusively consider the realized niche. Here we overcome this challenge by combining a physiologically mechanistic model of the fundamental niche with correlative models based on the realized niche to study the global invasion of the cane toad Rhinella marina. We find strong evidence that the success of R. marina in Australia reflects a shift in the species’ realized niche, as opposed to evolutionary shifts in range-limiting traits. Our results demonstrate that R. marina does not fill its fundamental niche in its native South American range and that areas of niche unfilling coincide with the presence of a closely related species with which R. marina hybridizes. Conversely, in Australia, where coevolved taxa are absent, R. marina largely fills its fundamental niche in areas behind the invasion front. The general approach taken here of contrasting fundamental and realized niche models provides key insights into the role of biotic interactions in shaping range limits and can inform effective management strategies not only for invasive species but also for assisted colonization under climate change.Understanding the factors that limit species’ geographic ranges has long stood as a fundamental goal in ecology (1) and is critical for making robust predictions of species’ range shifts as a result of climate change and biotic exchange. Niche theory (2) argues that species’ ranges are limited by physiological tolerances (which define the fundamental niche), as well as biotic interactions and dispersal barriers (which further constrain the fundamental niche to the realized niche), but the relative roles of these factors in shaping range limits remain poorly understood. Standard approaches to range prediction are based on correlations between species'' observed distributions and climate (i.e., the realized niche) (3, 4), and thus confound the influences of abiotic and biotic constraints on species’ ranges.Range shift projections based on correlative models also assume that species’ niches (both realized and fundamental) are conserved through space and time (3, 5, 6). However, there is growing evidence to suggest that species can undergo rapid niche shifts in novel environments (7–9) through either evolved environmental tolerances (fundamental niche shifts) (10, 11) or release from dispersal barriers or biotic constraints (realized niche shifts) (12, 13). Understanding whether such niche shifts are widespread in nature not only is important for validating the use of correlative models in climate change and invasive species impact assessments but also has implications for understanding patterns of community assembly and speciation (14, 15).Invasive species frequently experience release from biotic interactions and dispersal barriers in their invaded ranges (4, 12, 16), and thus provide model systems for investigating the degree to which niches are spatially and temporally conserved. Current approaches for examining niche shifts in invasive species primarily rely on comparisons of climates occupied by species in their native and invaded ranges (6, 7, 17, 18). However, such correlative comparisons fail to differentiate between the influences of adaptation after introduction and biotic interactions and dispersal barriers that are absent in a species’ invaded range. Here we present an approach that helps resolve this issue by integrating correlative niche models with mechanistic biophysical predictions of the fundamental niche (19). Biophysical models incorporate links between climate and an organism’s functional traits and are developed independent of a species’ current distribution. The biophysical approach thus provides a prediction of where a species can survive and reproduce in the absence of biotic interactions and dispersal limitations (19). We apply this mechanistic approach to investigate whether the invasion of Australia by the cane toad (Rhinella marina, formerly Bufo marinus) has been facilitated by a shift in the species’ realized or fundamental niche. Since its introduction to Australia in 1935 as a biological control agent, R. marina has expanded its range to include more than 1.2 million km² of the continent (20). This large-scale invasion has been facilitated by thermal acclimation (21, 22), as well as evolutionary shifts in locomotor performance (23). Have the environmental tolerances of toads evolved as well?     

Dopamine-associated cached values are not sufficient as the basis for action selection

Phasic dopamine transmission is posited to act as a critical teaching signal that updates the stored (or “cached”) values assigned to reward-predictive stimuli and actions. It is widely hypothesized that these cached values determine the selection among multiple courses of action, a premise that has provided a foundation for contemporary theories of decision making. In the current work we used fast-scan cyclic voltammetry to probe dopamine-associated cached values from cue-evoked dopamine release in the nucleus accumbens of rats performing cost–benefit decision-making paradigms to evaluate critically the relationship between dopamine-associated cached values and preferences. By manipulating the amount of effort required to obtain rewards of different sizes, we were able to bias rats toward preferring an option yielding a high-value reward in some sessions and toward instead preferring an option yielding a low-value reward in others. Therefore, this approach permitted the investigation of dopamine-associated cached values in a context in which reward magnitude and subjective preference were dissociated. We observed greater cue-evoked mesolimbic dopamine release to options yielding the high-value reward even when rats preferred the option yielding the low-value reward. This result identifies a clear mismatch between the ordinal utility of the available options and the rank ordering of their cached values, thereby providing robust evidence that dopamine-associated cached values cannot be the sole determinant of choices in simple economic decision making.In contemporary theories of economic decision making, values are assigned to reward-predictive states in which animals can take action to obtain rewards, and these state-action values are stored (“cached”) for the purpose of guiding future choices based upon their rank order (1–5). It is believed that these cached values are represented as synaptic weights within corticostriatal circuitry, reflected in the activity of subpopulations of striatal projection neurons (6–9), and are updated by dopamine-dependent synaptic plasticity (10–12). Indeed, a wealth of evidence suggests that the phasic activity of dopamine neurons reports instances in which current reward or expectation of future reward differs from current expectations (13–24). This pattern of activity resembles the prediction-error term from temporal-difference reinforcement-learning algorithms, which is considered the critical teaching signal for updating cached values. A notable feature of models that integrate dopamine transmission into this computational framework is that the cached value of an action is explicitly read out by the phasic dopamine response to the unexpected presentation of a cue that designates the transition into a state in which that action yields reward. Therefore, cue-evoked dopamine signaling provides a neural representation of the cached values of available actions, and if these cached values serve as the basis for action selection, then cue-evoked dopamine responses should be rank ordered in a manner that is consistent with animals’ behavioral preferences.Numerous studies that recorded cue-evoked dopamine signaling have reported correlations with the expected utility (subjective value) of actions (24–36). For example, risk-preferring rats demonstrated greater cue-evoked dopamine release for a risky option than for a certain option with equivalent objective expected value (reward magnitude times probability), whereas risk-averse rats showed greater dopamine release for the certain than for the risky option (30). Likewise, the cached values reported by dopamine neurons in macaque monkeys accounted for individual monkeys’ subjective flavor and risk preferences, with each attribute weighted according to its influence on behavioral preferences (31, 32). These observations, which are consistent across measures of dopamine neuronal activity and dopamine release, reinforce the prevailing notion that the dopamine-associated cached values could be the primary determinant of decision making (2–5, 17, 28–32) because the cue-evoked dopamine responses were rank ordered according to the animals’ subjective preferences. However, there have been some reports that other economic attributes, such as effortful response costs (35–38) or the overt aversiveness of an outcome (39), are represented inconsistently by cue-evoked dopamine responses. For example, Gan et al. (35) showed that independent manipulations of two different dimensions (reward magnitude and effort) that had equivalent effects on behavior did not have equivalent effects on dopamine release. Paralleling these findings, a recent report reached a similar conclusion that dopamine transmission preferentially encodes an appetitive dimension but is relatively insensitive to aversiveness (39).Because these cue-evoked dopamine signals represent cached values that are purported to determine action selection, their differential encoding of economic dimensions has potentially problematic implications in the context of decision making. Namely, by extrapolating from these studies (35–39), one might infer that when a decision involves the tradeoff between these economic dimensions, the rank order of the dopamine-associated cached values for each of the available options would not consistently reflect the ordinal utility of these options and therefore these cached values could not, on their own, be the basis of choices. However, this counterintuitive prediction was not tested explicitly by any of these previous studies; thus it remains a provocative notion that merits direct examination, because it is contrary to the prevailing hypothesis described above which is fundamental to contemporary theories of decision making. Therefore, we investigated interactions between dimensions that previously have been shown during independent manipulations to be weakly or strongly incorporated into these cached values. Specifically, we increased the amount of effort required to obtain a large reward so that animals instead preferred a low-effort option yielding a smaller reward, and we used fast-scan cyclic voltammetry to record cue-evoked mesolimbic dopamine release as a neurochemical proxy for each option’s cached value. These conditions permitted us to test whether the cached values reported via cue-evoked dopamine indeed align with animals’ subjective preferences across these mixed cost–benefit attributes.     

Effects of lymphocyte profile on development of EBV-induced lymphoma subtypes in humanized mice

Epstein-Barr virus (EBV) infection causes both Hodgkin’s lymphoma (HL) and non-Hodgkin’s lymphoma (NHL). The present study reveals that EBV-induced HL and NHL are intriguingly associated with a repopulated immune cell profile in humanized mice. Newborn immunodeficient NSG mice were engrafted with human cord blood CD34⁺ hematopoietic stem cells (HSCs) for a 8- or 15-wk reconstitution period (denoted ^8whN and ^15whN, respectively), resulting in human B-cell and T-cell predominance in peripheral blood cells, respectively. Further, novel humanized mice were established via engraftment of hCD34⁺ HSCs together with nonautologous fetal liver-derived mesenchymal stem cells (MSCs) or MSCs expressing an active notch ligand DLK1, resulting in mice skewed with human B or T cells, respectively. After EBV infection, whereas NHL developed more frequently in B-cell–predominant humanized mice, HL was seen in T-cell–predominant mice (P = 0.0013). Whereas human splenocytes from NHL-bearing mice were positive for EBV-associated NHL markers (hBCL2⁺, hCD20⁺, hKi67⁺, hCD20⁺/EBNA1⁺, and EBER⁺) but negative for HL markers (LMP1⁻, EBNA2⁻, and hCD30⁻), most HL-like tumors were characterized by the presence of malignant Hodgkin’s Reed–Sternberg (HRS)-like cells, lacunar RS (hCD30⁺, hCD15⁺, IgJ⁻, EBER⁺/hCD30⁺, EBNA1⁺/hCD30⁺, LMP⁺/EBNA2⁻, hCD68⁺, hBCL2⁻, hCD20^-/weak, Phospho STAT6⁺), and mummified RS cells. This study reveals that immune cell composition plays an important role in the development of EBV-induced B-cell lymphoma.Epstein Barr virus (EBV) infects human B lymphocytes and epithelial cells in >90% of the human population (1, 2). EBV infection is widely associated with the development of diverse human disorders that include Hodgkin’s lymphoma (HL) and non-Hodgkin’s lymphomas (NHL), including diffused large B-cell lymphoma (DLBCL), follicular B-cell lymphoma (FBCL), endemic Burkitt’s lymphoma (BL), and hemophagocytic lymphohistiocytosis (HLH) (3).HL is a malignant lymphoid neoplasm most prevalent in adolescents and young adults (4–6). Hodgkin/Reed–Sternberg (HRS) cells are the sole malignant cells of HL. HRS cells are characterized by CD30⁺/CD15⁺/BCL6⁻/CD20^+/− markers and appear large and multinucleated owing to multiple nuclear divisions without cytokinesis. Although HRS cells are malignant in the body, surrounding inflammatory cells greatly outnumber them. These reactive nonmalignant inflammatory cells, including lymphocytes, histiocytes, eosinophils, fibroblasts, neutrophils, and plasma cells, compose the vast majority of the tumor mass. The presence of HRS cells in the context of this inflammatory cellular background is a critical hallmark of the HL diagnosis (4). Approximately 50% of HL cases are EBV-associated (EBVaHL) (7–11). EBV-positive HRS cells express EBV latent membrane protein (LMP) 1 (LMP1), LMP2A, LMP2B, and EBV nuclear antigen (EBNA) 1 (EBNA1), but lack EBNA2 (latency II marker) (12). LMP1 is consistently expressed in all EBV-associated cases of classical HL (13, 14). LMP1 mimics activated CD40 receptors, induces NF-κB, and allows cells to become malignant while escaping apoptosis (15).The etiologic role of EBV in numerous disorders has been studied in humanized mouse models in diverse experimental conditions. Humanized mouse models recapitulate key characteristics of EBV infection-associated disease pathogenesis (16–24). Different settings have given rise to quite distinct phenotypes, including B-cell type NHL (DLBCL, FBCL, and unspecified B-cell lymphomas), natural killer/T cell lymphoma (NKTCL), nonmalignant lymphoproliferative disorder (LPD), extremely rare HL, HLH, and arthritis (16–24). Despite considerable efforts (16–24), EBVaHL has not been properly produced in the humanized mouse setting model, owing to inappropriate animal models and a lack of in-depth analyses. After an initial report of infected humanized mice, HRS-like cells appeared to be extremely rare in the spleens of infected humanized mice; however, the findings were inconclusive (18). Here we report direct evidence of EBVaHL or HL-like neoplasms in multiple humanized mice in which T cells were predominant over B cells. Our study demonstrates that EBV-infected humanized mice display additional EBV-associated pathogenesis, including DLBCL and hemophagocytic lymphohistiocytosis (16, 17).     

Application of desorption electrospray ionization mass spectrometry imaging in breast cancer margin analysis

Distinguishing tumor from normal glandular breast tissue is an important step in breast-conserving surgery. Because this distinction can be challenging in the operative setting, up to 40% of patients require an additional operation when traditional approaches are used. Here, we present a proof-of-concept study to determine the feasibility of using desorption electrospray ionization mass spectrometry imaging (DESI-MSI) for identifying and differentiating tumor from normal breast tissue. We show that tumor margins can be identified using the spatial distributions and varying intensities of different lipids. Several fatty acids, including oleic acid, were more abundant in the cancerous tissue than in normal tissues. The cancer margins delineated by the molecular images from DESI-MSI were consistent with those margins obtained from histological staining. Our findings prove the feasibility of classifying cancerous and normal breast tissues using ambient ionization MSI. The results suggest that an MS-based method could be developed for the rapid intraoperative detection of residual cancer tissue during breast-conserving surgery.Breast cancer is the most commonly diagnosed carcinoma in women in the United States and Western countries. Breast conservation surgery (BCS) has become the preferred treatment option for many women with early-stage breast cancer (1). BCS entails resection of the tumor, with a clean margin of normal tissue around it. Surgery is usually followed by radiation therapy. Results from seven large randomized prospective studies, with the largest two having over 20 y of follow-up, have shown equal survival when comparing BCS coupled with whole-breast radiation and mastectomy (2, 3).Normally, breast surgeons aim to remove a patient’s tumor, along with a rim of normal tissue that is free of cancer. Preoperative mammography, ultrasonography, or MRI may be used by the surgeon to guide adequate resection (4–6). Despite numerous improvements in imaging and surgical technique, the need for reexcision to achieve complete tumor resection in the United States typically ranges from 20–40% (7–15), and has been reported as being as high as 60% (16). The importance of reexcision is underscored by numerous studies, which have shown that incomplete resection of tumor and positive margins are associated with increased locoregional recurrence compared with negative margins (12, 17–20). Furthermore, the landmark meta-analysis performed by the Early Breast Cancer Trialists’ Collaborative Group (18, 21) directly linked local recurrence to survival, placing great emphasis on the surgeon’s role in minimizing local recurrence by obtaining adequate margins.Breast tumor reexcisions are accompanied by a number of undesirable problems: The completion of therapy is delayed, infection rates are increased, cost is increased, there can be a negative psychological impact on the patient, and there can be diminished aesthetic outcomes (22–24). The development of an intraoperative technique that allows the fast and accurate identification of residual tumor at surgical resection margins could decrease the reexcision rate, and therefore improve the care delivered to patients with cancer who are receiving BCS.To this end, multiple intraoperative methods have been explored, with various benefits as well as limitations. These methods include touch frozen section analysis (25), touch preparation cytology (26), specimen radiography (27, 28), rf spectroscopy (29, 30), Raman spectroscopy (31), radioguided occult lesion localization (32), near-IR fluorescence (33, 34), and high-frequency ultrasound (35–37). The intraoperative application of MRI, which has been successfully applied in brain surgery (38–42), is limited in its application in BCS. These limitations include MRI interpretation in the presence of acute surgical changes; lack of real-time imaging, requiring the interruption of surgery; and accurate localization of tumor based on images requiring development of fiducials (43–46).Mass spectrometry imaging (MSI) has been applied to investigate the molecular distribution of proteins, lipids, and metabolites without the use of labels (47, 48). In particular, the newly developed ambient ionization technique of desorption electrospray ionization (DESI) allows direct tissue analysis with little to no sample preparation (49, 50). Therefore, with the advantage of easy use, DESI-MSI has great potential in the application of intraoperative tumor assessment. The development of DESI-MSI enables the correlation of lipid distribution in two or three dimensions with tissue morphology (47, 51) and the distinction of cancerous from noncancerous tissues based on lipidomic information (52–54). Distinctive lipid profiles associated with different human cancers have been investigated by DESI-MSI (55–58). Moreover, the grades and subtypes of human brain tumors have been discriminated using this technique. Additionally, tumor margins have been delineated using DESI-MSI, and the results have been correlated with histopathological examination (59, 60).It has been reported that breast cancer demonstrates metabolic profiles that are distinct from those metabolic profiles found in normal breast tissue. This finding suggests a potential for using metabolite information for breast cancer diagnosis and tumor margin identification (61, 62). Here, we demonstrate an MS-based methodology for using lipidomic information to distinguish cancerous from noncancerous tissue and to delineate tumor boundaries.     

From the Cover: Neurons selective to the number of visual items in the corvid songbird endbrain

It is unknown whether anatomical specializations in the endbrains of different vertebrates determine the neuronal code to represent numerical quantity. Therefore, we recorded single-neuron activity from the endbrain of crows trained to judge the number of items in displays. Many neurons were tuned for numerosities irrespective of the physical appearance of the items, and their activity correlated with performance outcome. Comparison of both behavioral and neuronal representations of numerosity revealed that the data are best described by a logarithmically compressed scaling of numerical information, as postulated by the Weber–Fechner law. The behavioral and neuronal numerosity representations in the crow reflect surprisingly well those found in the primate association cortex. This finding suggests that distantly related vertebrates with independently developed endbrains adopted similar neuronal solutions to process quantity.Birds show elaborate quantification skills (1–3) that are of adaptive value in naturalistic situations like nest parasitism (4), food caching (5), or communication (6). The neuronal correlates of numerosity representations have only been explored in humans (7–9) and primates (10–18), and they have been found to reside in the prefrontal and posterior parietal neocortices. In contrast to primates, birds lack a six-layered neocortex. The birds’ lineage diverged from mammals 300 Mya (19), at a time when the neocortex had not yet developed from the pallium of the endbrain. Instead, birds developed different pallial parts as dominant endbrain structures (20, 21) based on convergent evolution, with the nidopallium caudolaterale (NCL) as a high-level association area (22–26). Where and how numerosity is encoded in vertebrates lacking a neocortex is unknown. Here, we show that neurons in the telencephalic NCL of corvid songbirds respond to numerosity and show a specific code for numerical information.     

Cerebral coherence between communicators marks the emergence of meaning

How can we understand each other during communicative interactions? An influential suggestion holds that communicators are primed by each other’s behaviors, with associative mechanisms automatically coordinating the production of communicative signals and the comprehension of their meanings. An alternative suggestion posits that mutual understanding requires shared conceptualizations of a signal’s use, i.e., “conceptual pacts” that are abstracted away from specific experiences. Both accounts predict coherent neural dynamics across communicators, aligned either to the occurrence of a signal or to the dynamics of conceptual pacts. Using coherence spectral-density analysis of cerebral activity simultaneously measured in pairs of communicators, this study shows that establishing mutual understanding of novel signals synchronizes cerebral dynamics across communicators’ right temporal lobes. This interpersonal cerebral coherence occurred only within pairs with a shared communicative history, and at temporal scales independent from signals’ occurrences. These findings favor the notion that meaning emerges from shared conceptualizations of a signal’s use.Human sociality is built on the capacity for mutual understanding, but its principles and mechanisms remain poorly understood (1). Given the pervasive ambiguity of communicative signals (2), how can we expect to understand each other? For instance, I might think of tacitly asking my friend Tom to enter a pub by virtue of a pointing gesture toward a nearby bike, believing that both of us recognized the bike of his girlfriend Emma, only to realize how my gesture would be interpreted differently as Tom tells me about his recent split from Emma (2, 3).An influential suggestion holds that communicators are mutually primed by each other’s behaviors, with associative mechanisms automatically coordinating the production of communicative signals and the comprehension of their meanings (4–8). In this framework, mutual understanding arises by virtue of individual experiences with a signal’s properties, as when linguistic features of a word are biased by recent experience of those features (9, 10). Alternatively, mutual understanding might require shared conceptualizations of a signal’s use, abstracted away from specific experiences during a communicative interaction (11–14). In this framework, mutual understanding arises from what communicators mutually know, “conceptual pacts” that are negotiated by communicators over the course of their interactions (11). Although both possibilities emphasize that communicative signals are context dependent (15), they put different emphasis on the relevance of the communicative signal. Both possibilities predict that mutual understanding is neurally implemented through temporally coherent and spatially overlapping activity across communicators (7, 16–18), but with different cerebral dynamics. If meaning is shared by virtue of signals’ features, then communicators’ cerebral coherence should be synchronized to the occurrence of those signals (7, 19, 20). If meaning is shared through conceptual pacts, then communicators’ cerebral coherence should be synchronized to abstractions generalized over multiple communicative episodes, without reference to the occurrence of a specific experience (1, 11, 14). Those predictions can be tested by manipulating the dynamics of mutual understanding across communicators, while capturing the dynamics of their interpersonal cerebral coherence.Mutual understanding was manipulated with an experimentally controlled communicative task (16, 21). This task precludes the use of communication channels and preexisting shared representations used during daily communication (e.g., a common idiom, body emblems, facial expressions), thereby gaining control over the communicative environment and the history of that environment (16, 21). The cerebral characteristics of mutual understanding were isolated through three nested analyses performed on functional magnetic resonance imaging (fMRI) activities simultaneously recorded in pairs of communicators engaged in understanding each other over a series of communicative interactions (22, 23). First, a model-based analysis isolated cerebral signals whose temporal profile matched the behavioral dynamics of mutual understanding observed across Communicators and Addressees. Second, a model-free analysis determined the frequency and phase characteristics of the interpersonal cerebral coherence of Communicator–Addressee pairs. Third, a model-based analysis tested whether interpersonal cerebral coherence in Communicator–Addressee pairs is specifically driven by the creation of novel shared meanings, independently from responses to transient signals.     

Long-term exposure to elevated CO2 enhances plant community stability by suppressing dominant plant species in a mixed-grass prairie

Climate controls vegetation distribution across the globe, and some vegetation types are more vulnerable to climate change, whereas others are more resistant. Because resistance and resilience can influence ecosystem stability and determine how communities and ecosystems respond to climate change, we need to evaluate the potential for resistance as we predict future ecosystem function. In a mixed-grass prairie in the northern Great Plains, we used a large field experiment to test the effects of elevated CO₂, warming, and summer irrigation on plant community structure and productivity, linking changes in both to stability in plant community composition and biomass production. We show that the independent effects of CO₂ and warming on community composition and productivity depend on interannual variation in precipitation and that the effects of elevated CO₂ are not limited to water saving because they differ from those of irrigation. We also show that production in this mixed-grass prairie ecosystem is not only relatively resistant to interannual variation in precipitation, but also rendered more stable under elevated CO₂ conditions. This increase in production stability is the result of altered community dominance patterns: Community evenness increases as dominant species decrease in biomass under elevated CO₂. In many grasslands that serve as rangelands, the economic value of the ecosystem is largely dependent on plant community composition and the relative abundance of key forage species. Thus, our results have implications for how we manage native grasslands in the face of changing climate.Ecologists have long recognized the importance of climate in shaping plant communities across spatial and temporal scales (1). Together, precipitation and temperature characterize the distribution of terrestrial biomes across the globe. As climate changes, some biomes will be more vulnerable to temperature increase (2) or altered precipitation (3), whereas others will be more resistant (4–6). Ecological stability, the maintenance of community structure and function despite climatic fluctuation or disturbance (7–9), includes two components: resistance [lack of change despite perturbation (9)] and resilience [return to a previous state following a perturbation (10–13)]. Diversity (14) and productivity (11, 15) can both influence community stability (16) and dampen responses to environmental perturbation (5, 9, 17, 18). What remains unclear is how stability and resistance respond to predicted changes in climate.Multiple climate change factors simultaneously impact plant performance, community structure, and productivity (4, 19, 20). For example, elevated CO₂ can improve water use efficiency and increase plant productivity (21–23), but warming can reduce it, counteracting the positive water-saving effects of elevated CO₂ (24). In addition, plant species and functional groups that differ in photosynthetic pathway often have contrasting responses to elevated CO₂, warming, and altered precipitation. Furthermore, the effects of individual climate change factors may be additive (25, 26), subadditive (4, 24, 27), or antagonistic (27, 28). As a result, the performance of a given species or functional group depends on interactions among CO₂, temperature, and soil characteristics that influence plant water availability at the community level.Globally, both elevated CO₂ and warming are expected to lead to pronounced changes in vegetation distribution and structure (25, 29, 30). In North American grasslands, warming is expected to promote C₄ dominance, dampening the ability of these areas to show large responses to elevated CO₂ (25). Because responses to climate change differ among individual plant species and depend on community context (31–33), the resultant community dynamics are difficult to predict. In addition, plant responses to climate manipulations can shift over time. Our earlier work in a mixed-grass prairie shows that in the first 3 y of the Prairie Heating and CO₂ Enrichment (PHACE) experiment, both C₃ and C₄ grass production benefited from elevated CO₂ conditions (34). However, long-term studies of CO₂ enrichment show that plant responses can diminish over time (22, 35), including the responses of dominant grass species in our mixed-grass prairie (36). To accurately characterize the trajectory of species responses and predict the interacting impacts of global climate change on plant community structure and function, long-term experiments are necessary.Grasslands in the northern Great Plains are experiencing rapid climate change, with average annual temperatures increasing by 2.6 °C over the last century and winter and spring temperatures increasing more rapidly than summer temperatures (37). Grasslands are extensively grazed, and moisture availability (timing and amount of rainfall) affects grassland productivity to support domestic and native herbivores (3, 38). Compared with other regions, precipitation change is expected to be relatively modest, but there is a general consensus that even if annual precipitation change is small, precipitation timing will become increasingly variable (37) and the number of extreme precipitation events will also increase (39–41). When coupled with rising temperatures, water limitation will increase (42), potentially reducing rangeland productivity (43). Because the timing of water availability regulates grassland productivity and community dynamics (3, 44), variation in background climate may promote or reduce the resistance of grasslands to climate change. The economic value of the ecosystem is largely dependent on the plant community and the relative abundance of key forage grass species (45). Thus, changes in grassland productivity can have clear economic impacts for ranching and managing wildlife (46).To understand how climate change influences plant community dynamics and stability (namely, resistance to interannual shifts in precipitation), we quantified the impacts of experimentally imposed elevated CO₂, warming, and summer irrigation on plant community composition and aboveground biomass production over 8 y in a northern mixed-grass prairie in southeastern Wyoming. Species that dominate biomass production are expected to respond to changes in climate most directly (47), whereas subdominant species may respond to climate change directly and indirectly through their interactions with the dominant species (6, 48, 49). Thus, we quantified climate change effects on the entire community and on dominant and subdominant community members separately. We addressed three questions: (i) Do the effects of climate change on plant community composition and productivity depend on temperature and precipitation variation? (ii) Do dominant and subdominant components of the plant community respond differently to climate change? and (iii) What is the influence of climate change on community composition and biomass stability?     

The evolution of self-control

Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.Since Darwin, understanding the evolution of cognition has been widely regarded as one of the greatest challenges for evolutionary research (1). Although researchers have identified surprising cognitive flexibility in a range of species (2–40) and potentially derived features of human psychology (41–61), we know much less about the major forces shaping cognitive evolution (62–71). With the notable exception of Bitterman’s landmark studies conducted several decades ago (63, 72–74), most research comparing cognition across species has been limited to small taxonomic samples (70, 75). With limited comparable experimental data on how cognition varies across species, previous research has largely relied on proxies for cognition (e.g., brain size) or metaanalyses when testing hypotheses about cognitive evolution (76–92). The lack of cognitive data collected with similar methods across large samples of species precludes meaningful species comparisons that can reveal the major forces shaping cognitive evolution across species, including humans (48, 70, 89, 93–98).To address these challenges we measured cognitive skills for self-control in 36 species of mammals and birds (Fig. 1 and Tables S1–S4) tested using the same experimental procedures, and evaluated the leading hypotheses for the neuroanatomical underpinnings and ecological drivers of variance in animal cognition. At the proximate level, both absolute (77, 99–107) and relative brain size (108–112) have been proposed as mechanisms supporting cognitive evolution. Evolutionary increases in brain size (both absolute and relative) and cortical reorganization are hallmarks of the human lineage and are believed to index commensurate changes in cognitive abilities (52, 105, 113–115). Further, given the high metabolic costs of brain tissue (116–121) and remarkable variance in brain size across species (108, 122), it is expected that the energetic costs of large brains are offset by the advantages of improved cognition. The cortical reorganization hypothesis suggests that selection for absolutely larger brains—and concomitant cortical reorganization—was the predominant mechanism supporting cognitive evolution (77, 91, 100–106, 120). In contrast, the encephalization hypothesis argues that an increase in brain volume relative to body size was of primary importance (108, 110, 111, 123). Both of these hypotheses have received support through analyses aggregating data from published studies of primate cognition and reports of “intelligent” behavior in nature—both of which correlate with measures of brain size (76, 77, 84, 92, 110, 124).Open in a separate windowFig. 1.A phylogeny of the species included in this study. Branch lengths are proportional to time except where long branches have been truncated by parallel diagonal lines (split between mammals and birds ∼292 Mya).With respect to selective pressures, both social and dietary complexities have been proposed as ultimate causes of cognitive evolution. The social intelligence hypothesis proposes that increased social complexity (frequently indexed by social group size) was the major selective pressure in primate cognitive evolution (6, 44, 48, 50, 87, 115, 120, 125–141). This hypothesis is supported by studies showing a positive correlation between a species’ typical group size and the neocortex ratio (80, 81, 85–87, 129, 142–145), cognitive differences between closely related species with different group sizes (130, 137, 146, 147), and evidence for cognitive convergence between highly social species (26, 31, 148–150). The foraging hypothesis posits that dietary complexity, indexed by field reports of dietary breadth and reliance on fruit (a spatiotemporally distributed resource), was the primary driver of primate cognitive evolution (151–154). This hypothesis is supported by studies linking diet quality and brain size in primates (79, 81, 86, 142, 155), and experimental studies documenting species differences in cognition that relate to feeding ecology (94, 156–166).Although each of these hypotheses has received empirical support, a comparison of the relative contributions of the different proximate and ultimate explanations requires (i) a cognitive dataset covering a large number of species tested using comparable experimental procedures; (ii) cognitive tasks that allow valid measurement across a range of species with differing morphology, perception, and temperament; (iii) a representative sample within each species to obtain accurate estimates of species-typical cognition; (iv) phylogenetic comparative methods appropriate for testing evolutionary hypotheses; and (v) unprecedented collaboration to collect these data from populations of animals around the world (70).Here, we present, to our knowledge, the first large-scale collaborative dataset and comparative analysis of this kind, focusing on the evolution of self-control. We chose to measure self-control—the ability to inhibit a prepotent but ultimately counterproductive behavior—because it is a crucial and well-studied component of executive function and is involved in diverse decision-making processes (167–169). For example, animals require self-control when avoiding feeding or mating in view of a higher-ranking individual, sharing food with kin, or searching for food in a new area rather than a previously rewarding foraging site. In humans, self-control has been linked to health, economic, social, and academic achievement, and is known to be heritable (170–172). In song sparrows, a study using one of the tasks reported here found a correlation between self-control and song repertoire size, a predictor of fitness in this species (173). In primates, performance on a series of nonsocial self-control control tasks was related to variability in social systems (174), illustrating the potential link between these skills and socioecology. Thus, tasks that quantify self-control are ideal for comparison across taxa given its robust behavioral correlates, heritable basis, and potential impact on reproductive success.In this study we tested subjects on two previously implemented self-control tasks. In the A-not-B task (27 species, n = 344), subjects were first familiarized with finding food in one location (container A) for three consecutive trials. In the test trial, subjects initially saw the food hidden in the same location (container A), but then moved to a new location (container B) before they were allowed to search (Movie S1). In the cylinder task (32 species, n = 439), subjects were first familiarized with finding a piece of food hidden inside an opaque cylinder. In the following 10 test trials, a transparent cylinder was substituted for the opaque cylinder. To successfully retrieve the food, subjects needed to inhibit the impulse to reach for the food directly (bumping into the cylinder) in favor of the detour response they had used during the familiarization phase (Movie S2).Thus, the test trials in both tasks required subjects to inhibit a prepotent motor response (searching in the previously rewarded location or reaching directly for the visible food), but the nature of the correct response varied between tasks. Specifically, in the A-not-B task subjects were required to inhibit the response that was previously successful (searching in location A) whereas in the cylinder task subjects were required to perform the same response as in familiarization trials (detour response), but in the context of novel task demands (visible food directly in front of the subject).