Evaluating the roles of the inferior frontal gyrus and superior parietal lobule in deductive reasoning: an rTMS study

This study used off-line repetitive transcranial magnetic stimulation (rTMS) to examine the roles of the superior parietal lobule (SPL) and inferior frontal gyrus (IFG) in a deductive reasoning task. Subjects performed a categorical syllogistic reasoning task involving congruent, incongruent, and abstract trials. Twenty four subjects received magnetic stimulation to the SPL region prior to the task. In the other 24 subjects, TMS was administered to the IFG region before the task. Stimulation lasted for 10min, with an inter-pulse frequency of 1Hz. We found that bilateral SPL (Brodmann area (BA) 7) stimulation disrupted performance on abstract and incongruent reasoning. Left IFG (BA 45) stimulation impaired congruent reasoning performance while paradoxically facilitating incongruent reasoning performance. This resulted in the elimination of the belief-bias. In contrast, right IFG stimulation only impaired incongruent reasoning performance, thus enhancing the belief-bias effect. These findings are largely consistent with the dual-process theory of reasoning, which proposes the existence of two different human reasoning systems: a belief-based heuristic system; and a logic-based analytic system. The present findings suggest that the left language-related IFG (BA 45) may correspond to the heuristic system, while bilateral SPL may underlie the analytic system. The right IFG may play a role in blocking the belief-based heuristic system for solving incongruent reasoning trials. This study could offer an insight about functional roles of distributed brain systems in human deductive reasoning by utilizing the rTMS approach.     

The Quadruple Process model approach to examining the neural underpinnings of prejudice

In order to investigate the systems underlying the automatic and controlled processes that support social attitudes, we conducted an fMRI study that combined an implicit measure of race attitudes with the Quadruple Process model (Quad model). A number of previous neural investigations have adopted the Implicit Association Test (IAT) to examine the automatic processes that contribute to social attitudes. Application of the Quad model builds on this previous research by permitting measures of distinct automatic and controlled processes that contribute to performance on the IAT. The present research found that prejudiced attitudes of ingroup favoritism were associated with amygdala, medial and right lateral orbitofrontal cortex. In contrast, prejudiced attitudes of outgroup negativity were associated with caudate and left lateral orbitofrontal cortex. Frontal regions found in previous neural research on the IAT, such as anterior cingulate, dorsolateral prefrontal cortex and operculum were associated with detecting appropriate responses in situations in which they conflict with automatic associations. Insula activity was associated with attitudes towards ingroup and outgroup members, as well as detecting appropriate behavior.     

An fMRI study of violations of social expectations: when people are not who we expect them to be

The current study examines the effect of violations of social expectancies on the neural substrates of person perception. In an event-related fMRI experiment, participants were presented with the photographs of either Republican or Democrat politicians paired with either typical Republican or Democrat political views (e.g., "wants a smaller government" or "wants liberal supreme court judges"). Subjects were asked to form an impression of the targets using information about both their political affiliation and their political views. Of interest was the contrast between stereotypically congruent trials and stereotypically incongruent trials. The results reveal that brain regions previously involved in mentalizing (i.e., temporoparietal junction and medial prefrontal cortex) are preferentially recruited when viewing incongruent social targets.     

Neural correlates of distance and congruity effects in a numerical Stroop task: an event-related fMRI study

This study aimed at investigating the neural correlates of a number-size congruity task. Using an event-related fMRI design, we presented one-digit number pairs to 17 participants in a number-size interference task that required subjects to focus on one stimulus property (e.g., numerical size) and to ignore the other (physical size). In different blocks, participants were asked to decide which digit of a digit pair was numerically larger (numerical comparison task) or physically larger (physical comparison task). Stimuli were classified into three categories: (a) congruent: physical and numerical comparison leads to the same response; (b) incongruent: physical and numerical comparison leads to different responses; (c) neutral: the stimuli differ only with regard to the task-relevant stimulus property. Behavioral results reflect robust distance effects (quicker reaction times for long distances relative to short ones) and size congruity effects (longer reaction times for incongruent relative to congruent stimuli) in both tasks. Imaging results reveal that-compared to congruent trials-incongruent trials led to a stronger activation in the dorsolateral prefrontal cortex and the anterior cingulate cortex, areas associated with attentional control. The distance effect (neutral condition only) led to a stronger activation in bilateral parietal areas including the intraparietal sulcus (IPS).     

Task constraints modulate activation in right ventral lateral prefrontal cortex

Lesion data suggest that right prefrontal cortex (PFC) plays a critical role in open-ended problem solving. To test this hypothesis, we scanned fifteen normal subjects with fMRI as they completed three types of anagram problems varying in the level of constraints placed on the search space. On unconstrained trials, they rearranged letters to generate solutions (e.g., Can you make a "Word with ZJAZ?"). On semantically constrained trials, they rearranged letters to generate solutions within particular semantic categories (e.g., Can you make a type of "Music with ZJAZ?"). On baseline trials, they rearranged letters to make specific words (e.g., Can you make the word "JAZZ with ZJAZ?"). As predicted, the critical comparison of unconstrained vs. semantically constrained trials revealed significant activation in right ventral lateral PFC, as well as left superior frontal gyrus, frontopolar cortex, right superior parietal lobe, right post central gyrus, and the occipital-parietal sulcus. Furthermore, activation in right ventral lateral PFC (BA 47) increased as the constraints placed on the anagram search space were reduced. We argue that the activation in right ventral lateral PFC is related to hypothesis generation in unconstrained settings, whereas activation in other structures is related to additional processes linked to anagram problems such as semantic retrieval, semantic categorization, and cognitive monitoring. These results extend the lesion data and imaging studies by demonstrating that a relative absence of constraints on the solution space is sufficient to engage right ventral lateral PFC in hypothesis generation tasks.     

The Inhibition of Imitative Response Tendencies

Recent neurocognitive studies show that perception and execution of actions are intimately linked. The mere observation of an action seems to evoke a tendency to execute that action. Since such imitative response tendencies are not adaptive in many everyday situations imitative response tendencies usually have to be inhibited. These inhibitory processes have never been investigated using brain imaging techniques. Former work on response inhibition and interference control has focused on paradigms such as the Stroop task or the go/no-go task. We have carried out an event-related functional magnetic resonance imaging study in order to investigate the cortical mechanisms underlying the inhibition of imitative responses. The experiment employs a simple response task in which subjects were instructed to execute predefined finger movements (tapping or lifting of the index finger) in response to an observed congruent or incongruent finger movement (tapping or lifting). A comparison of brain activation in incongruent and congruent trials revealed strong activation in the dorsolateral prefrontal cortex (middle frontal gyrus) and activation in the right frontopolar cortex and the right anterior parietal cortex, as well as in the precuneus. These results support the assumption of prefrontal involvement in response inhibition and extend this assumption to a "new" class of prepotent responses, namely, to imitative actions.     

Getting mixed messages: The impact of conflicting social signals on the brain's target emotional response

Amidst a barrage of sensory information in the environment, the impact that individual stimuli have on our behaviour is thought to depend on the outcome of competition that occurs within and between multiple brain regions. Although biased competition models of attention have been tested in visual cortices and to a lesser extent in auditory cortex, little is known about the nature of stimulus competition outside of sensory areas. Given the hypothesized role of multiple pathways (cortical and subcortical) and specialized brain regions for processing valence information, studies involving conflicting basic emotional stimuli provide a unique opportunity to examine whether the principles of biased competition apply outside of sensory cortex. We used fMRI to examine the neural representation and resolution of emotional conflict in a sample of healthy individuals. Participants made explicit judgments about the valence of happy or fearful target facial expressions in the context of emotionally congruent, neutral, or incongruent distracters. The results suggest that emotional conflict is reflected in a dissociable manner across distinct neural regions. Posterior areas of visual cortex showed enhanced responding to congruent relative to neutral or incongruent stimuli. Orbitofrontal cortex remained sensitive to positive affect in the context of conflicting emotional stimuli. In contrast, within the amygdala, activity associated with identifying positive target expressions declined with the introduction of neutral and incongruent expressions; however, activity associated with fearful target expressions was less susceptible to the influence of emotional context. Enhanced functional connectivity was observed between medial prefrontal cortex and the amygdala during incongruent trials; the degree of connectivity was correlated with reaction time costs incurred during incongruent trials. The results are interpreted with reference to current models of emotional attention and regulation.     

Acute tryptophan depletion improves performance and modulates the BOLD response during a Stroop task in healthy females

To gain more insight into the effect of low brain serotonin (5-HT) on brain activation related to conflict, the present study examined the effect of acute tryptophan depletion (ATD) on performance and the blood oxygen level dependent (BOLD) response during a combined cognitive and emotional Stroop task. Fifteen healthy female volunteers were tested during a placebo and tryptophan depletion session in an event-related fMRI design. ATD improved performance during Stroop interference. Two effects of ATD on the BOLD response were found. Firstly, ATD increased the BOLD response in the anterior cingulate cortex (ACC) (BA 32) when incongruent color words were compared with congruent color words in the first Stroop block the participants performed. Secondly, ATD increased the BOLD response in the left precuneus (BA 31) and cuneus (BA 18) during congruent color words. ATD did not affect the BOLD response accompanying emotional stimuli. However, we showed that ATD increased the interference of negative words on color naming. This finding was explained in terms of an emotional processing bias in favor of negative words, which leads to stronger interference of these words. In line with previous studies, the present study showed that a temporary reduction of 5-HT improved Stroop performance and changed the underlying brain activation pattern in healthy female participants. Moreover, we replicated our previous finding that ATD modulated the BOLD response in the dorsomedial prefrontal cortex during tasks that require cognitive control.     

Caught in the act: the impact of audience on the neural response to morally and socially inappropriate behavior

We examined the impact of witnesses on the neural response to moral and social transgressions using fMRI. In this study, participants (N=16) read short vignettes describing moral and social transgressions in the presence or absence of an audience. In line with our hypothesis, ventrolateral (BA 47) and dorsomedial (BA 8) frontal cortex showed increased BOLD responses to moral transgressions regardless of audience and to social transgressions in the presence of an audience relative to neutral situations. These findings are consistent with the suggestion that these regions of prefrontal cortex modify behavioral responses in response to social cues. Greater activity was observed in left temporal-parietal junction, medial prefrontal cortex and temporal poles to moral and to a lesser extent social transgressions relative to neutral stories, regardless of audience. These regions have been implicated in the representation of the mental states of others (Theory of Mind). The presence of an audience was associated with increased left amygdala activity across all conditions.     

Cognitive control explored by linear modelling behaviour and fMRI data during Stroop tasks

Most previous neuroimaging studies of Stroop paradigms have not provided sufficient information about the relationship between response times (RTs) and imaging signals. The objective of the present study is to build a linear model to explore the relationship between RTs and imaging signals. Neural information in Stroop tasks under the preconditions of high conflict and adjustment was extracted by using a method of modifying the ratio of congruent trials to incongruent trials in blocks. It was shown that the signals of the dorsal lateral prefrontal cortex (DLPFC) were negatively associated with the RTs for high-ratio trials in both blocks, and the signals of the anterior cingulate cortex (ACC) were negatively associated with the RTs for incongruence in high-conflict blocks. These results suggest that the DLPFC and ACC have more effects on executive modification and conflict monitoring, respectively.     

A PET investigation of the attribution of intentions with a nonverbal task

Several authors have demonstrated that theory of mind is associated with a cerebral pattern of activity involving the medial prefrontal cortex. This study was designed to determine the cerebral regions activated during attribution of intention to others, a task which requires theory-of-mind skills. Eight healthy subjects performed three nonverbal tasks using comic strips while PET scanning was performed. One condition required subjects to attribute intentions to the characters of the comic strips. The other two conditions involved only physical logic and knowledge about objects' properties: one condition involved characters, whereas the other only represented objects. The comparison of the attribution of intention condition with the physical logic with characters condition was associated with rCBF increases in the right middle and medial prefrontal cortex including Brodmann's area (BA) 9, the right inferior prefrontal cortex (BA 47), the right inferior temporal gyrus (BA 20), the left superior temporal gyrus (BA 38), the left cerebellum, the bilateral anterior cingulate, and the middle temporal gyri (BA 21). The comparison of the physical logic with characters condition and the physical logic without characters condition showed the activation of the lingual gyri (BA 17, 18, 19), the fusiform gyri (BA 37), the middle (BA 21) and superior (BA 22, 38) temporal gyri on both sides, and the posterior cingulate. These data suggest that attribution of intentions to others is associated with a complex cerebral activity involving the right medial prefrontal cortex when a nonverbal task is used. The laterality of this function is discussed.     

Isolation of saccade inhibition processes: rapid event-related fMRI of saccades and nogo trials

Previous functional magnetic resonance imaging (fMRI) studies have compared saccade trials and nogo trials, which required subjects to look at peripheral visual stimuli and to inhibit automatic saccades evoked by peripheral stimuli, respectively. These studies surprisingly reported no activation differences in cortical saccade regions between the two tasks, despite their opposite response requirements. Here, we re-examined this issue by comparing saccades and nogo trials using a rapid event-related fMRI design in which saccade trials were presented twice as frequently as nogo trials to make the saccade response more prepotent. We hypothesized that this should increase recruitment of response inhibition processes in the nogo task, thereby increasing fMRI activation on nogo trials. Saccade and nogo trials were presented in whole and half trial versions. Whereas whole trials included a trial type instruction followed by peripheral stimulus presentation and subject response, half trials included only the instruction component, allowing us to measure instruction-related activation separately from response-evoked signals for both saccades and nogo trials. Instruction-related activation was greater for nogo versus saccade trials in right frontal eye field, middle frontal gyrus, intraparietal sulcus, and precuneus, which we attribute to a mixture of preparatory and task switching processes. Response-related activation was greater for nogo trials in supplementary eye field, anterior cingulate cortex, inferior frontal gyrus, and right supramarginal gyrus, and we attribute these results to saccade inhibition and other processes associated with an increased requirement for inhibition of the automatic saccade in nogo trials.     

Information Framing Reduces Initial Negative Attitudes in Cancer Patients' Decisions About Hospice Care

Background

Negative attitudes toward hospice care might prevent patients with cancer from discussing and choosing hospice as they approach end of life. When making a decision, people often naturally focus on either expected benefits or the avoidance of harm. Behavioral research has demonstrated that framing information in an incongruent manner with patients' underlying motivational focus reduces their negative attitudes toward a disliked option.

Top down influence on visuo-tactile interaction modulates neural oscillatory responses

Multisensory integration involves bottom-up as well as top-down processes. We investigated the influences of top-down control on the neural responses to multisensory stimulation using EEG recording and time-frequency analyses. Participants were stimulated at the index or thumb of the left hand, using tactile vibrators mounted on a foam cube. Simultaneously they received a visual distractor from a light emitting diode adjacent to the active vibrator (spatially congruent trial) or adjacent to the inactive vibrator (spatially incongruent trial). The task was to respond to the elevation of the tactile stimulus (upper or lower), while ignoring the simultaneous visual distractor. To manipulate top-down control on this multisensory stimulation, the proportion of spatially congruent (vs. incongruent) trials was changed across blocks. Our results reveal that the behavioral cost of responding to incongruent than congruent trials (i.e., the crossmodal congruency effect) was modulated by the proportion of congruent trials. Most importantly, the EEG gamma band response and the gamma-theta coupling were also affected by this modulation of top-down control, whereas the late theta band response related to the congruency effect was not. These findings suggest that gamma band response is more than a marker of multisensory binding, being also sensitive to the correspondence between expected and actual multisensory stimulation. By contrast, theta band response was affected by congruency but appears to be largely immune to stimulation expectancy.     

Dual-process model in semantic priming: A functional imaging perspective.

In this positron emission tomography study, we investigated the neural correlates of semantic priming, where response to a word is facilitated when preceded by a semantically related word. Nine normal subjects were scanned while performing a lexical decision task. Within this condition, the proportion of related prime-target word pairs was varied across scans from 0 to 100%. The control task involved letter decision on consonant letter strings, controlling orthographic processing and response selection. First, lexical decision (relative to letter decision) activated regions previously observed in lexicosemantic tasks, i.e., the left anterior and inferior temporal lobe and left inferior frontal gyrus. Behavioral analysis confirmed significant facilitation of lexical decision to related targets (mean priming effect 68 ms). It also suggested the contribution of both automatic and strategic processes, consistent with theoretical accounts of priming. Automatic priming was indicated by consistent RTs to related targets irrespective of the proportion of related word pairs per scan. Strategic processing was indicated by decreases in RTs to nonwords as the proportion of related targets increased. Nonlinear correlational analysis of cerebral activity during lexical decision revealed a neurophysiological correlate of these behavioral effects in (i) the left anterior temporal lobe (BA 38), a region involved in lexicosemantic processing; (ii) the anterior cingulate cortex, right premotor region (BA 6), and right superior parietal lobe (BA 7), regions associated with attentional processes. We conclude that in this experimental context, semantic priming involves both automatic and strategic processing.     

Reading anomalous sentences: an event-related fMRI study of semantic processing

We report a random-effects analysis of an event-related fMRI study (n = 28) of cerebral activity during the reading of sentences that ended with a word that was either congruent or incongruent with the previous sentence context. Event-related potential studies have shown that this task elicits a late negativity peaking around 400 ms poststimulus (N400) that is larger for incongruent than for congruent sentence endings. A direct comparison of the activation for incongruent words versus that for congruent words revealed significantly greater activation for incongruent words than congruent words in bilateral inferior frontal and inferio-medial temporal cortex, left lateral frontal cortex, left posterior fusiform gyrus, bilateral motor cortex, and supplementary motor area. These results are consistent with data from intracranial electrical recording studies of the N400 electrical potential. The results are discussed as they relate to the localization of the cerebral sites underlying semantic processing in general and the localization of the scalp recorded N400 event-related potential in particular.     

The neural basis of belief encoding and integration in moral judgment

Moral judgment in the mature state depends on "theory of mind", or the capacity to attribute mental states (e.g., beliefs, desires, and intentions) to moral agents. The current study uses functional magnetic resonance imaging (fMRI) to investigate the cognitive processes for belief attribution in moral judgment. Participants read vignettes in a 2x2x2 design: protagonists produced either a negative or neutral outcome, based on the belief that they were causing the negative outcome or the neutral outcome; presentation of belief information either preceded or followed outcome information. In each case, participants judged the moral permissibility of the action. The results indicate that while the medial prefrontal cortex is recruited for processing belief valence, the temporo-parietal junction and precuneus are recruited for processing beliefs in moral judgment via two distinct component processes: (1) encoding beliefs and (2) integrating beliefs with other relevant features of the action (e.g., the outcome) for moral judgment.     

Heritability of anterior cingulate response to conflict: an fMRI study in female twins

Interference processing requires increased focus on relevant dimensions of environmental stimuli and selective allocation of attentional resources, in order to filter extraneous information and inhibit non-adaptive responses. This process is important in everyday life and is necessary for responding to novel and challenging situations. Dorsal anterior cingulate cortex (dACC) is involved in this process, and behavioral twin studies indicate that performance on interference processing tasks is highly heritable. However, the extent to which dACC activation related to such tasks is influenced by genetic factors has not been reported. In the current study, 10 pairs of monozygotic and 10 pairs of dizygotic female twins performed a validated interference processing task during fMRI. There were three main results: (1) increased dACC activation for incongruent (INC) minus congruent (CON) trials was observed; (2) dACC activation for INC minus CON trials was both moderately heritable and significantly correlated with the difference in reaction time (RT) between INC and CON trials; (3) RT for INC trials was moderately heritable. RT for CON trials and the latency difference between INC and CON trials were not influenced significantly by genetic factors. The current study provides the first functional imaging evidence that dACC activation during interference processing is significantly influenced by genes. These results suggest an endophenotype that may be applied to various psychiatric disorders that are both highly heritable and associated with altered dACC function.     

Of cats and women: temporal dynamics in the right temporoparietal cortex reflect auditory categorical processing of vocalizations

Understanding the temporal dynamics underlying cortical processing of auditory categories is complicated by difficulties in equating temporal and spectral features across stimulus classes. In the present magnetoencephalography (MEG) study, female voices and cat sounds were filtered so as to match in most of their acoustic properties, and the respective auditory evoked responses were investigated with a paradigm that allowed us to examine auditory cortical processing of two natural sound categories beyond the physical make-up of the stimuli. Three cat or human voice sounds were first presented to establish a categorical context. Subsequently, a probe sound that was congruent, incongruent, or ambiguous to this context was presented. As an index of a categorical mismatch, MEG responses to incongruent sounds were stronger than the responses to congruent sounds at ~250 ms in the right temporoparietal cortex, regardless of the sound category. Furthermore, probe sounds that could not be unambiguously attributed to any of the two categories ("cat" or "voice") evoked stronger responses after the voice than cat context at 200-250 ms, suggesting a stronger contextual effect for human voices. Our results suggest that categorical templates for human and animal vocalizations are established at ~250 ms in the right temporoparietal cortex, likely reflecting continuous online analysis of spectral stimulus features during auditory categorizing task.     

The role of the prefrontal cortex in controlling gender-stereotypical associations: a TMS investigation

Stereotypes associated with gender, race, ethnicity and religion are powerful forces in human social interactions. Previous neuroimaging and neuropsychological studies point to a role of the prefrontal cortex in controlling stereotypical responses. Here we used transcranial magnetic stimulation (TMS) in combination with an Implicit Association Test (IAT) to highlight the possible causal role of the left dorsolateral prefrontal cortex (DLPFC) and the right anterior dorsomedial prefrontal cortex (aDMPFC) in controlling gender-stereotypical responses. Young male and female participants were tested. Our results showed that applying TMS over the left DLPFC and the right aDMPFC increased the gender-stereotypical bias in male participants compared to when TMS was applied to a control site (vertex). This suggests that both the left DLPFC and the right aDMPFC play a direct role in stereotyping. Females did not show a significant gender bias on the IAT; correspondingly their responses were unaffected by TMS.