Electrophysiological evidence for the left-lateralized effect of language on preattentive categorical perception of color

Previous studies have shown that the effect of language on categorical perception of color is stronger when stimuli are presented in the right visual field than in the left. To examine whether this lateralized effect occurs preattentively at an early stage of processing, we monitored the visual mismatch negativity, which is a component of the event-related potential of the brain to an unfamiliar stimulus among a temporally presented series of stimuli. In the oddball paradigm we used, the deviant stimuli were unrelated to the explicit task. A significant interaction between color-pair type (within-category vs. between-category) and visual field (left vs. right) was found. The amplitude of the visual mismatch negativity component evoked by the within-category deviant was significantly smaller than that evoked by the between-category deviant when displayed in the right visual field, but no such difference was observed for the left visual field. This result constitutes electroencephalographic evidence that the lateralized Whorf effect per se occurs out of awareness and at an early stage of processing.     

Global versus local processing of frequency-modulated tones in gerbils: an animal model of lateralized auditory cortex functions

Hemispheric asymmetries of speech and music processing might arise from more basic specializations of left and right auditory cortex (AC). It is not clear, however, whether such asymmetries are unique to humans, i.e., consequences of speech and music, or whether comparable lateralized AC functions exist in nonhuman animals, as evolutionary precursors. Here, we investigated the cortical lateralization of perception of linearly frequency-modulated (FM) tones in gerbils, a rodent species with human-like low-frequency hearing. Using a footshock-reinforced shuttle-box avoidance go/no-go procedure in a total of 178 gerbils, we found that (i) the discrimination of direction of continuous FM (rising versus falling sweeps, 250-ms duration) was impaired by right but not left AC lesions; (ii) the discrimination of direction of segmented FM (50-ms segments, 50-ms silent gaps, total duration 250 ms) was impaired by bilateral but not unilateral AC lesions; (iii) the discrimination of gap durations (10-30 ms) in segmented FM was impaired by left but not right AC lesions. AC lesions before and after training resulted in similar effects. Together, these experiments suggest that right and left AC, even in rodents, use different strategies in analyzing FM stimuli. Thus, the right AC, by using global cues, determines the direction of continuous and segmented FM but cannot discriminate gap durations. The left AC, by using local cues, discriminates gap durations and determines FM direction only when additional segmental information is available.     

Language regions of brain are operative in color perception

The effect of language on the categorical perception of color is stronger for stimuli in the right visual field (RVF) than in the left visual field, but the neural correlates of the behavioral RVF advantage are unknown. Here we present brain activation maps revealing how language is differentially engaged in the discrimination of colored stimuli presented in either visual hemifield. In a rapid, event-related functional MRI study, we measured subjects'' brain activity while they performed a visual search task. Compared with colors from the same lexical category, discrimination of colors from different linguistic categories provoked stronger and faster responses in the left hemisphere language regions, particularly when the colors were presented in the RVF. In addition, activation of visual areas 2/3, responsible for color perception, was much stronger for RVF stimuli from different linguistic categories than for stimuli from the same linguistic category. Notably, the enhanced activity of visual areas 2/3 coincided with the enhanced activity of the left posterior temporoparietal language region, suggesting that this language region may serve as a top-down control source that modulates the activation of the visual cortex. These findings shed light on the brain mechanisms that underlie the hemifield- dependent effect of language on visual perception.     

Hemispheric differences in processing of vocalizations depend on early experience

An intriguing phenomenon in the neurobiology of language is lateralization: the dominant role of one hemisphere in a particular function. Lateralization is not exclusive to language because lateral differences are observed in other sensory modalities, behaviors, and animal species. Despite much scientific attention, the function of lateralization, its possible dependence on experience, and the functional implications of such dependence have yet to be clearly determined. We have explored the role of early experience in the development of lateralized sensory processing in the brain, using the songbird model of vocal learning. By controlling exposure to natural vocalizations (through isolation, song tutoring, and muting), we manipulated the postnatal auditory environment of developing zebra finches, and then assessed effects on hemispheric specialization for communication sounds in adulthood. Using bilateral multielectrode recordings from a forebrain auditory area known to selectively process species-specific vocalizations, we found that auditory responses to species-typical songs and long calls, in both male and female birds, were stronger in the right hemisphere than in the left, and that right-side responses adapted more rapidly to stimulus repetition. We describe specific instances, particularly in males, where these lateral differences show an influence of auditory experience with song and/or the bird’s own voice during development.     

Language affects patterns of brain activation associated with perceptual decision

Well over half a century ago, Benjamin Lee Whorf [Carroll JB (1956) Language, Thought, and Reality: Selected Writings of Benjamin Lee Whorf (MIT Press, Cambridge, MA)] proposed that language affects perception and thought and is used to segment nature, a hypothesis that has since been tested by linguistic and behavioral studies. Although clear Whorfian effects have been found, it has not yet been demonstrated that language influences brain activity associated with perception and/or immediate postperceptual processes (referred hereafter as "perceptual decision"). Here, by using functional magnetic resonance imaging, we show that brain regions mediating language processes participate in neural networks activated by perceptual decision. When subjects performed a perceptual discrimination task on easy-to-name and hard-to-name colored squares, largely overlapping cortical regions were identified, which included areas of the occipital cortex critical for color vision and regions in the bilateral frontal gyrus. Crucially, however, in comparison with hard-to-name colored squares, perceptual discrimination of easy-to-name colors evoked stronger activation in the left posterior superior temporal gyrus and inferior parietal lobule, two regions responsible for word-finding processes, as demonstrated by a localizer experiment that uses an explicit color patch naming task. This finding suggests that the language-processing areas of the brain are directly involved in visual perceptual decision, thus providing neuroimaging support for the Whorf hypothesis.     

汉字阅读加工的功能磁共振研究进展

对阅读基本机制的了解是研究失读症发病机制和对失读症进行康复治疗的基础。功能磁共振成像是一种能显示活体脑内神经活动状态的成像方法,近年来被用于语言学尤其是汉字阅读加工机制的研究。本文对汉字单字加工的偏侧化以及是否存在汉字认知加工的特异脑区等进行综述。     

Dominant hemisphere lateralization of cortical parasympathetic control as revealed by frontotemporal dementia

The brain continuously influences and perceives the physiological condition of the body. Related cortical representations have been proposed to shape emotional experience and guide behavior. Although previous studies have identified brain regions recruited during autonomic processing, neurological lesion studies have yet to delineate the regions critical for maintaining autonomic outflow. Even greater controversy surrounds hemispheric lateralization along the parasympathetic–sympathetic axis. The behavioral variant of frontotemporal dementia (bvFTD), featuring progressive and often asymmetric degeneration that includes the frontoinsular and cingulate cortices, provides a unique lesion model for elucidating brain structures that control autonomic tone. Here, we show that bvFTD is associated with reduced baseline cardiac vagal tone and that this reduction correlates with left-lateralized functional and structural frontoinsular and cingulate cortex deficits and with reduced agreeableness. Our results suggest that networked brain regions in the dominant hemisphere are critical for maintaining an adaptive level of baseline parasympathetic outflow.The brain controls peripheral autonomic physiology by perceiving the ambient condition of the body and continuously adjusting autonomic tone to maintain homeostasis (1–3). Theorists have long postulated that physiological body states provide a foundation for emotion and feeling (3–7). Bodily states also shape perception and motivate behavior. The appeal of cold water on a hot summer day or the aversion to socializing when feeling sick demonstrate the intimate link between homeostatic regulation and emotional–motivational processing (2). The autonomic nervous system exerts direct control over bodily states via its two major branches: the sympathetic system, associated with energy mobilization, and the parasympathetic system, whose peripheral efferent signals are conveyed chiefly via the vagus nerve and are associated with energy conservation at the whole organism level (8). Perturbations in one or both of these systems are associated with homeostatic instability and diverse pathological feeling states (1, 9–14). Therefore, elucidating the neural mechanisms of autonomic integration represents an important biomedical research priority.Although the peripheral and brainstem organization of the autonomic nervous system has been well-characterized, especially in nonhuman laboratory mammals (8), how the human cerebral cortex represents and influences the internal milieu remains less clear (4). Task-activation functional MRI (fMRI) and neurological lesion studies suggest that anterior peri-allocortical transition cortices, especially the frontoinsula (FI) (also referred to as ventral anterior insula) and anterior cingulate cortices (ACCs) and midcingulate cortices (MCCs), constitute the cortical autonomic control centers [see reviews by Craig (3), Critchley (4), Thayer et al. (15), and Seeley et al. (16)]. These regions share a close structural and functional relationship and anchor a large-scale intrinsic connectivity network referred to in the neuroimaging literature as the salience network [Seeley et al. (17)]. Although the ACC and FI coactivate in response to diverse emotionally significant stimuli (4, 18), the FI is regarded as an interoceptive sensory association cortex representing afferent information and the ACC as the visceromotor structure that drives autonomic efference (3, 16, 18–20). Some authors have proposed that left-sided (dominant hemisphere) forebrain structures, such as the ACC and anterior insula (aIns), are predominantly involved with maintaining parasympathetic tone whereas homotopic right (nondominant) forebrain regions control sympathetic tone and responses (21–23).Although appealing, the lateralization model of autonomic control remains controversial (24). Some uncertainty reflects the challenge of detecting lateralized fMRI activations within a system characterized by opponent organization (coordinated and balanced coactivation of physiologically complementary modules). Lesion studies have suffered from small sample sizes and issues relating to whether the lesion produced loss of function or pathophysiological excitation of the affected tissue, producing inconsistent findings across studies (14, 24, 25).To overcome these challenges, we studied cortical autonomic control in patients with behavioral variant frontotemporal dementia (bvFTD) using a lesion-based structural and functional imaging approach. BvFTD is characterized by a progressive deterioration of social–emotional functions and diminished phasic autonomic responses during social–emotional tasks (26, 27). Anatomically, bvFTD involves degeneration of core salience network structures proposed to support autonomic regulation, including the ACC and anterior midcingulate cortex (aMCC), FI, and subcortical, limbic, and brainstem sites (28, 29). With graded, often asymmetric damage localized to the relevant network, bvFTD provides an important yet unexplored lesion model for clarifying the neuroanatomy of autonomic control.Here, we show that patients with bvFTD exhibit diminished basal cardiac vagal tone. Four convergent task-free fMRI analyses revealed that lower cardiac vagal tone was associated with perturbed connectivity in the pregenual and subgenual ACC and FI, predominantly on the left side. Consistent with this leftward functional lateralization, more severe atrophy within the left than right ACC and FI predicted lower cardiac vagal tone and lower agreeableness, an emotional trait that has been associated with vagal tone and fosters social relationships by promoting concern for others (30–33). These findings provide compelling evidence that human cortical parasympathetic control is critically dependent upon a left-lateralized network anchored by the ACC and FI.     

Binaural jitter improves interaural time-difference sensitivity of cochlear implantees at high pulse rates

Interaural time difference (ITD) arises whenever a sound outside of the median plane arrives at the two ears. There is evidence that ITD in the rapidly varying fine structure of a sound is most important for sound localization and for understanding speech in noise. Cochlear implants (CIs), neural prosthetic devices that restore hearing in the profoundly deaf, are increasingly implanted to both ears to provide implantees with the advantages of binaural hearing. CI listeners have been shown to be sensitive to fine structure ITD at low pulse rates, but their sensitivity declines at higher pulse rates that are required for speech coding. We hypothesize that this limitation in electric stimulation is at least partially due to binaural adaptation associated with periodic stimulation. Here, we show that introducing binaurally synchronized jitter in the stimulation timing causes large improvements in ITD sensitivity at higher pulse rates. Our experimental results demonstrate that a purely temporal trigger can cause recovery from binaural adaptation. Thus, binaurally jittered stimulation may improve several aspects of binaural hearing in bilateral recipients of neural auditory prostheses.     

Categorical perception of color is lateralized to the right hemisphere in infants, but to the left hemisphere in adults

Both adults and infants are faster at discriminating between two colors from different categories than two colors from the same category, even when between- and within-category chromatic separation sizes are equated. For adults, this categorical perception (CP) is lateralized; the category effect is stronger for the right visual field (RVF)-left hemisphere (LH) than the left visual field (LVF)-right hemisphere (RH). Converging evidence suggests that the LH bias in color CP in adults is caused by the influence of lexical color codes in the LH. The current study investigates whether prelinguistic color CP is also lateralized to the LH by testing 4- to 6-month-old infants. A colored target was shown on a differently colored background, and time to initiate an eye movement to the target was measured. Target background pairs were either from the same or different categories, but with equal target-background chromatic separations. Infants were faster at initiating an eye movement to targets on different-category than same-category backgrounds, but only for targets in the LVF-RH. In contrast, adults showed a greater category effect when targets were presented to the RVF-LH. These results suggest that whereas color CP is stronger in the LH than RH in adults, prelinguistic CP in infants is lateralized to the RH. The findings suggest that language-driven CP in adults may not build on prelinguistic CP, but that language instead imposes its categories on a LH that is not categorically prepartitioned.     

Phonological decisions require both the left and right supramarginal gyri

Recent functional imaging studies demonstrated that both the left and right supramarginal gyri (SMG) are activated when healthy right-handed subjects make phonological word decisions. However, lesion studies typically report difficulties with phonological processing after left rather than right hemisphere damage. Here, we used a unique dual-site transcranial magnetic stimulation (TMS) approach to test whether the SMG in the right hemisphere contributes to modality-independent (i.e., auditory and visual) phonological decisions. To test task-specificity, we compared the effect of real or sham TMS during phonological, semantic, and perceptual decisions. To test laterality and anatomical specificity, we compared the effect of TMS over the left, right, or bilateral SMG and angular gyri. The accuracy and reaction times of phonological decisions were selectively disrupted relative to semantic and perceptual decisions when real TMS was applied over the left, right, or bilateral SMG. These effects were not observed for TMS over the angular gyri. A follow-up experiment indicated that the threshold-intensity for inducing a disruptive effect on phonological decisions was identical for unilateral TMS over the right or left SMG. Taken together, these findings provide converging evidence that the right SMG contributes to accurate and efficient phonological decisions in the healthy brain, with no evidence that the left and right SMG can compensate for one another during TMS. Our findings motivate detailed studies of phonological processing in patients with acute or long-term damage of the right SMG.     

PET and MRI show differences in cerebral asymmetry and functional connectivity between homo- and heterosexual subjects

Cerebral responses to putative pheromones and objects of sexual attraction were recently found to differ between homo- and heterosexual subjects. Although this observation may merely mirror perceptional differences, it raises the intriguing question as to whether certain sexually dimorphic features in the brain may differ between individuals of the same sex but different sexual orientation. We addressed this issue by studying hemispheric asymmetry and functional connectivity, two parameters that in previous publications have shown specific sex differences. Ninety subjects [25 heterosexual men (HeM) and women (HeW), and 20 homosexual men (HoM) and women (HoW)] were investigated with magnetic resonance volumetry of cerebral and cerebellar hemispheres. Fifty of them also participated in PET measurements of cerebral blood flow, used for analyses of functional connections from the right and left amygdalae. HeM and HoW showed a rightward cerebral asymmetry, whereas volumes of the cerebral hemispheres were symmetrical in HoM and HeW. No cerebellar asymmetries were found. Homosexual subjects also showed sex-atypical amygdala connections. In HoM, as in HeW, the connections were more widespread from the left amygdala; in HoW and HeM, on the other hand, from the right amygdala. Furthermore, in HoM and HeW the connections were primarily displayed with the contralateral amygdala and the anterior cingulate, in HeM and HoW with the caudate, putamen, and the prefrontal cortex. The present study shows sex-atypical cerebral asymmetry and functional connections in homosexual subjects. The results cannot be primarily ascribed to learned effects, and they suggest a linkage to neurobiological entities.     

From the Cover: Syllabic discrimination in premature human infants prior to complete formation of cortical layers

The ontogeny of linguistic functions in the human brain remains elusive. Although some auditory capacities are described before term, whether and how such immature cortical circuits might process speech are unknown. Here we used functional optical imaging to evaluate the cerebral responses to syllables at the earliest age at which cortical responses to external stimuli can be recorded in humans (28- to 32-wk gestational age). At this age, the cortical organization in layers is not completed. Many neurons are still located in the subplate and in the process of migrating to their final location. Nevertheless, we observed several points of similarity with the adult linguistic network. First, whereas syllables elicited larger right than left responses, the posterior temporal region escaped this general pattern, showing faster and more sustained responses over the left than over the right hemisphere. Second, discrimination responses to a change of phoneme (ba vs. ga) and a change of human voice (male vs. female) were already present and involved inferior frontal areas, even in the youngest infants (29-wk gestational age). Third, whereas both types of changes elicited responses in the right frontal region, the left frontal region only reacted to a change of phoneme. These results demonstrate a sophisticated organization of perisylvian areas at the very onset of cortical circuitry, 3 mo before term. They emphasize the influence of innate factors on regions involved in linguistic processing and social communication in humans.     

Global topological dominance in the left hemisphere

A series of experiments with right-handers demonstrated that the left hemisphere (LH) is reliably and consistently superior to the right hemisphere (RH) for global topological perception. These experiments generalized the topological account of lateralization to different kinds of topological properties (including holes, inside/outside relation, and “presence vs. absence”) in comparison with a broad spectrum of geometric properties, including orientation, distance, size, mirror-symmetry, parallelism, collinearity, etc. The stimuli and paradigms used were also designed to prevent subjects from using various nontopological properties in performing the tasks of topological discrimination. Furthermore, task factors commonly considered in the study of hemispheric asymmetry, such as response latency vs. accuracy, vertical vs. horizontal presentation, detection vs. recognition, and simultaneous vs. sequential judgment, were manipulated to not be confounding factors. Moreover, left-handed subjects were tested and showed the right lateralization of topological perception, in the opposite direction of lateralization compared with right-handers. In addition, the functional magnetic resonance imaging measure revealed that only a region in the left temporal gyrus was consistently more activated across subjects in the task of topological discrimination, consistent with the behavioral results. In summary, the global topological dominance in the LH is well supported by the converging evidence from the variety of paradigms and techniques, and it suggests a unified solution to the current major controversies on visual lateralization.     

Symmetries in human brain language pathways correlate with verbal recall

Lateralization of language to the left hemisphere is considered a key aspect of human brain organization. We used diffusion tensor MRI to perform in vivo virtual dissection of language pathways to assess the relationship between brain asymmetry and cognitive performance in the normal population. Our findings suggest interhemispheric differences in direct connections between Broca's and Wernicke's territories, with extreme leftward lateralization in more than half of the subjects and bilateral symmetrical distribution in only 17.5% of the subjects. Importantly, individuals with more symmetric patterns of connections are better overall at remembering words using semantic association. Moreover, preliminary analysis suggests females are more likely to have a symmetrical pattern of connections. These findings suggest that the degree of lateralization of perisylvian pathways is heterogeneous in the normal population and, paradoxically, bilateral representation, not extreme lateralization, might ultimately be advantageous for specific cognitive functions.     

Diagnostic Value of Bilateral Petrosal Sinus Sampling in Children with Cushing Disease: A Multi-center Study

Objective:Although the sensitivity and specificity of bilateral inferior petrosal sinus sampling (BIPSS) were shown to be quite high in adult patients, pediatric studies are limited in number and have conflicting results, since BIPSS is much less commonly performed in children. The aim of this study was to assess the role of BIPSS in the detection and accuracy of lateralization of pituitary adenomas in pediatric patients with Cushing disease (CD) and its possible advantage over other diagnostic methods.Methods:This was a multicenter, nationwide, web-based study. The diagnostic value of BIPSS in 16 patients, aged between four and 16.5 years with a confirmed diagnosis of CD, was evaluated retrospectively. The sensitivity and specificity of BIPSS and magnetic resonance imaging (MRI) were calculated, and compared statistically.Results:Standard tests, except for morning cortisol level, were effective in proving the presence of Cushing syndrome. While MRI findings were consistent with microadenoma in eight cases (50%), CD presence and lateralization was successfully predicted in 14 of 16 patients using BIPSS. BIPSS compared with MRI examination was significantly more accurate, both in pre-stimulation and post-stimulation results (p=0.047 and p=0.041, respectively). BIPSS showed a significantly higher sensitivity (92.8%) than MRI in detecting the pituitary source of adrenocorticotropic hormone secretion.Conclusion:These results suggest that BIPSS is superior to MRI for diagnostic work-up to confirm the diagnosis of CD. Moreover, in line with previous studies, BIPSS was shown to provide better information about adenoma location, which is vital for possible surgical intervention.     

Differential mRNA expression of alpha and beta estrogen receptor isoforms and GnRH in the left and right side of the preoptic and anterior hypothalamic area during the estrous cycle of the rat

Asymmetric mRNA expression was found in preoptic anterior and hypothalamic anterior areas of the two estrogen receptor isoforms and the gonadotropin-releasing hormone. On the right side of these areas, estrogen receptor alpha mRNA expression reached its peak on estrus day, while on the left side the peak was reached on proestrus day. Estrogen receptor beta mRNA expression peaked on both sides on the same day, diestrous-2 day, but at different hours, showing a sustained expression for the next measured hour on the left side, while peaking and dropping abruptly on the right side. Gonadotropin-releasing hormone also peaked on both sides on diestrous-2 day, being the left side peak expression significantly lower than the peak expression at the right side. The side expression differences suggest that different sides of the before mentioned areas may play different roles of endocrine reproductive functions, while differences of expression at different times may suggest interaction between sides for the same functions.     

晚期胰腺癌患者凝血、抗凝功能的变化及意义

检测２２例晚期胰腺癌患者的凝血酶原时间（ＰＴ）、激活的部分凝血酶原时间（ＡＰＴＴ）、纤维蛋白原（Ｆｇ）、ｖｉｌｌｅ ｂｒａｎｄ因子（ＶＷＦ）等凝血指标及抗凝血酶Ⅲ活性（ＡＴ－ⅢＡ）、抗凝血酶Ⅲ抗原（ＡＴ－ⅢＡｇ）、Ｃ蛋白活性（ＰＣ：Ａ）等抗凝指标，并与正常人进行对比分析。结果显示：是期胰腺癌患者的ＰＴ、ＡＰＴＴ明显延长（Ｐ〈０．０１），Ｆｆ、ＶＷＦ升高（Ｐ〈０．０１），ＡＴ－ⅢＡ％降低（Ｐ〈０．０