Dendritic asymmetry cannot account for directional responses of neurons in visual cortex

Serotonin transporter characteristics in lymphocytes and platelets of male aggressive schizophrenia patients compared to non-aggressive schizophrenia patients

A large body of literature indicates that disturbances of central serotonin (5-HT) function play an important role in aggressive behavior. Results from open-label and placebo-controlled trials as well as the reported inverse relationship between 5-HT function and aggression in human subjects, suggest that reduced 5-HT activity is associated with aggressive behavior. The activity of the 5-HT transporter (5-HTT), as determined by [(3)H]5-HT uptake to blood lymphocytes, was measured in 20 currently aggressive and 20 non-aggressive male schizophrenia patients. In addition, the pharmacodynamic characteristics of platelet 5-HTT were assessed by [(3)H]citalopram binding. There were no significant differences in the density (B(max)) of platelet [(3)H]citalopram binding sites between the two groups. Similarly, the dissociation constant (K(d)) values were indistinguishable. The maximum uptake velocity (V(max)) of [(3)H]5-HT to fresh lymphocytes and the K(m) values of the 5-HT to the transporter were significantly higher in currently aggressive compared to the non-aggressive schizophrenia patients. The association of high V(max) values with current aggressive behavior provides further support to the involvement of the 5-HTT in aggressive behavior as well as to the efficacy of 5-HTT blockers in the control of aggression. The role of the various components of the serotonergic system in the pathophysiology and treatment of aggressive behavior in schizophrenia needs to be further evaluated.

The Simulated Gambling Paradigm Applied to Young Adults: An Examination of University Students' Performance

Simulated gambling tasks have become popular as sensitive tools for identifying individuals with real-time impairment in decision making. Various clinical samples, especially patients with damage to the ventromedial prefrontal cortex, perform poorly on these tasks. The patients typically persist in choosing risky (disadvantageous) card decks instead of switching to safer (advantageous) decks. In terms of Damasio's (1994) somatic marker hypothesis, the poor performance stems from defective integration of emotional and rational aspects of decision making. Less information is available about performance in healthy populations, particularly young adults. After administering a computerized gambling task to 141 university students, we found that individuals in this population also tend to prefer disadvantageous decks to advantageous decks. The results indicate that performance is governed primarily by the frequency of positive outcomes on a trial-by-trial basis rather than by the accumulation of winnings in the longer term. These findings are discussed in light of the cognitive literature pertaining to the simulated gambling paradigm.

Neural networks in frontotemporal dementia--a meta-analysis

OBJECTIVE

Frontotemporal dementia is the most common form of frontotemporal lobar degeneration. It is characterized by deep alterations in behavior and personality. We conducted a systematic and quantitative meta-analysis to examine its neural correlates and place the disease in a framework of cognitive neuropsychiatry.

METHODS

MedLine and Current Contents search engines were used to identify imaging studies investigating frontotemporal dementia between 1980 and 2005. Nine studies were identified reporting either atrophy or decreases in glucose utilization. Finally, the analysis involved 132 patients and 166 controls. A quantitative meta-analysis was performed. Maxima of the studies resulted in activation likelihood estimates.

RESULTS

The meta-analysis revealed a particularly frontomedian network impaired in frontotemporal dementia. Additionally, right anterior insula, and medial thalamus were identified.

CONCLUSIONS

Our study specifies frontotemporal dementia as the frontomedian variant of frontotemporal lobar degeneration. The disease affects neural networks enabling self-monitoring, theory of mind capabilities, processing/evaluation of internal mental states, perception of pain and emotions, and sustaining personality and self. Our study contributes to placing frontotemporal dementia in cognitive neuropsychiatry.

Les visages et leurs émotions

In this second part, we address particularly the question of the neural mechanisms and structures involved in the recognition of facial emotional expressions that are crucial in social cognition. Emotion recognition in others can be critically impaired in some neurodegenerative and neurovascular diseases. That dysfunction sometimes correlated to disabling behavioural disorders and interpersonal communication impairment must be further understood. The results of a series of scalp and intracranial event related potential recordings, as well as recent advances in the literature, are reported. ERPs to facial emotional expressions were thus recorded in multiple subcortical and cortical areas in drug refractory epileptical patients implanted with depth electrodes. The roles of amygdala, insula and prefrontal cortex located at crossroads between perceptive analysis and emotional conceptual knowledge are particularly underlined. Altogether, these studies demonstrate that facial expressions are widely processed in space and time, some structures reacting very early and automatically, others providing a sustained reaction depending on the attention.

Decision-making in obesity: a study using the Gambling Task

The present study addresses the issue of whether a "decision-making disorder" could account for the behavioral problems of severely obese patients (BMI score >34) who are not classified by traditional psychiatric Eating Disorder tests. The neuropsychological test employed, the Gambling Task (GT), is not directly related to the food domain, but it is sensitive to failure in making long-term advantageous choices. A comparison was made of 20 obese subjects (OS) and 20 normal-weight subjects (NWS) matched in age, education and IQ. The subjects' personalities and food behavior were assessed from psychological questionnaires, and then the Gambling Task was administered. The number of "good" choices made by the two groups during GT performance differed significantly, and the OS did not learn to maximize advantageous choices like the NWS did. OS behavior could be consistent with a prefrontal cortex defect that implies difficulties in inhibition of excessive food intake.

Revisiting the role of the prefrontal cortex in the pathophysiology of attention-deficit/hyperactivity disorder

Most neural models for the pathophysiology of attention-deficit/hyperactivity disorder (ADHD) have centered on the prefrontal cortex and its interconnections with the striatum and other subcortical structures. However, research only partially supports these models, and they do not correspond with the development of the prefrontal cortex and its interrelated neurocircuitry. The neural and functional development of the prefrontal cortex more closely parallels recovery from ADHD as indicated by the developmental remission of symptomatology. The authors hypothesize that ADHD is due to noncortical dysfunction that manifests early in ontogeny, remains static throughout the lifetime, and is not associated with the remission of symptomatology. Data supporting this neurodevelopmental model of prefrontal cortex function in ADHD are reviewed. Research and treatment implications are discussed.

Decision-making after traumatic brain injury in children: a preliminary study

Decision-making under conditions of uncertainty was studied in 11 children with moderate to severe post-acute traumatic brain injury (TBI) using a modification of the Iowa Gambling Task (Bechara et al., 1994). We hypothesized that decision-making would be compromised in children with TBI. The results revealed that when divided into subgroups by lesion location, children with lesions in the amygdala (AM) were impaired on modified gambling task performance, but children with ventromedial (VM) lesions did not appear to be impaired on the task. These results are in contrast to studies of decision-making in adults with focal lesions of vascular etiology.

Differentiating among prefrontal substrates in psychopathy: neuropsychological test findings

Frontal lobe and consequent executive dysfunction have long been related to psychopathy. More recently, there have been suggestions that specific regions of frontal cortex, rather than all of frontal cortex, may be implicated in psychopathy. To examine this issue, the authors presented 25 individuals with psychopathy and 30 comparison individuals with measures preferentially indexing the orbitofrontal cortex (OFC; object alternation task), dorsolateral prefrontal cortex (DLPFC; spatial alternation task), and anterior cingulate cortex (ACC; number-Stroop reading and counting tasks). The individuals with psychopathy showed significant impairment on the measure preferentially sensitive to OFC functioning. In contrast, the 2 groups did not show impairment on the measures preferentially sensitive to the functioning of the DLPFC or ACC. These results are interpreted with reference to executive dysfunction accounts of the disorder.

The effects of orbital frontal cortex damage on the modulation of defensive responses by rats in playful and nonplayful social contexts

In a series of 3 experiments on rats, 2 hypotheses were tested: (a) that damage to the orbital frontal cortex (OFC) would alter the socially relevant context for executing defensive responses but not their performance and (b) that damage done to the OFC in early infancy would produce more deficits in social behavior than similar damage occurring in adulthood. Bilateral or unilateral OFC damage in adult males did not impair their ability to defend themselves during play fighting and when protecting their food but did impair their ability to modify the pattern of defense in response to different partners. Rats that sustained bilateral damage at 3 days of age not only had deficits in partner-related modulation of defense but also exhibited hyperactivity in their play. The findings thus supported the proposed hypotheses.

The neural basis of implicit moral attitude—An IAT study using event-related fMRI

Recent models of morality have suggested the importance of affect-based automatic moral attitudes in moral reasoning. However, previous investigations of moral reasoning have frequently relied upon explicit measures that are susceptible to voluntary control. To investigate participant's automatic moral attitudes, we used a morality Implicit Association Test (IAT). Participants rated the legality of visually depicted legal and illegal behaviors of two different intensity levels (e.g., high intensity illegal = interpersonal violence; low intensity illegal = vandalism) both when the target concept (e.g., illegal) was behaviorally paired with an associated attribute (e.g., bad; congruent condition) or an unassociated attribute (e.g., good; incongruent condition). Behaviorally, an IAT effect was shown; RTs were faster in the congruent rather than incongruent conditions. At the neural level, implicit moral attitude, as indexed by increased BOLD response as a function of stimulus intensity, was associated with increased activation in the right amygdala and the ventromedial orbitofrontal cortex. In addition, performance on incongruent trials relative to congruent trials was associated with increased activity in the right ventrolateral prefrontal cortex (BA 47), left subgenual cingulate gyrus (BA 25), bilateral premotor cortex (BA 6) and the left caudate. The functional contributions of these regions in moral reasoning are discussed.

Doing the right thing: A common neural circuit for appropriate violent or compassionate behavior

Humans have a considerable facility to adapt their behavior in a manner that is appropriate to social or societal context. A failure of this ability can lead to social exclusion and is a feature of disorders such as psychopathy and disruptive behavior disorder. We investigated the neural basis of this ability using a customized video game played by 12 healthy participants in an fMRI scanner. Two conditions involved extreme examples of context-appropriate action: shooting an aggressive humanoid assailant or healing a passive wounded person. Two control conditions involved carefully matched stimuli paired with inappropriate actions: shooting the person or healing the assailant. Surprisingly, the same circuit, including the amygdala and ventromedial prefrontal cortex, was activated when participants acted in a context-appropriate manner, whether being compassionate towards an injured conspecific or aggressive towards a violent assailant. The findings indicate a common system that guides behavioral expression appropriate to social or societal context irrespective of its aggressive or compassionate nature.

What frontotemporal dementia reveals about the neurobiological basis of morality

There is evidence that moral behavior is a product of evolution and an innate aspect of the human brain. Functional magnetic resonance studies in normals, investigations of psychopaths, and acquired sociopathy from brain lesions suggest a neurobiology of moral behavior. Reports of sociopathy among patients with frontotemporal dementia (FTD) have provided a further opportunity to clarify the neurobiology of morality. They confirm a morality network that includes the ventromedial frontal cortex, the orbitofrontal cortex, and the amygdalae. The right ventromedial region is critical for the emotional tagging of moral situations, the orbitofrontal cortex responds to social cues and mitigates impulsive reactions, and the amygdalae are necessary for threat detection and moral learning. Alterations in moral behavior in FTD may result from a loss of the emotional label of moral dilemmas, coupled with disinhibited responses. More investigations are needed to fully understand how the brain mediates moral or ethical behavior.

Social cognition: a multi level analysis

This paper investigates the construct of social cognition from an interdisciplinary perspective blending social psychology and cognitive neuroscience. This perspective argues for the inclusion of processes used to decode and encode the self, other people and interpersonal knowledge in the definition of social cognition. The neural modularity of social cognition is considered. The paper concludes by considering a number of challenges for social cognition research including questions of accuracy and the influence of motivation and bias in social cognitive processing.

Where is the spike generator of the cochlear nerve? Voltage-gated sodium channels in the mouse cochlea

The origin of the action potential in the cochlea has been a long-standing puzzle. Because voltage-dependent Na+ (Nav) channels are essential for action potential generation, we investigated the detailed distribution of Nav1.6 and Nav1.2 in the cochlear ganglion, cochlear nerve, and organ of Corti, including the type I and type II ganglion cells. In most type I ganglion cells, Nav1.6 was present at the first nodes flanking the myelinated bipolar cell body and at subsequent nodes of Ranvier. In the other ganglion cells, including type II, Nav1.6 clustered in the initial segments of both of the axons that flank the unmyelinated bipolar ganglion cell bodies. In the organ of Corti, Nav1.6 was localized in the short segments of the afferent axons and their sensory endings beneath each inner hair cell. Surprisingly, the outer spiral fibers and their sensory endings were well labeled beneath the outer hair cells over their entire trajectory. In contrast, Nav1.2 in the organ of Corti was localized to the unmyelinated efferent axons and their endings on the inner and outer hair cells. We present a computational model illustrating the potential role of the Nav channel distribution described here. In the deaf mutant quivering mouse, the localization of Nav1.6 was disrupted in the sensory epithelium and ganglion. Together, these results suggest that distinct Nav channels generate and regenerate action potentials at multiple sites along the cochlear ganglion cells and nerve fibers, including the afferent endings, ganglionic initial segments, and nodes of Ranvier.

Acute infantile encephalopathy predominantly affecting the frontal lobes

To establish a novel subtype of acute infantile encephalopathy, the clinical and radiologic features of nine infants with acute encephalopathy involving the bilateral frontal lobes were examined. These patients had convulsive status epilepticus with hyperpyrexia followed by a prolonged impairment of consciousness for 2-20 days. After the recovery of consciousness, all the patients manifested regression of verbal function and lack of spontaneity. Some of them also exhibited stereotypic movements, instability of mood, or catalepsy. Transient postictal edema in both frontal lobes was suggested by diffusion-weighted magnetic resonance imaging. Attenuated cerebral perfusion in the frontal lobes was demonstrated by single-photon emission computed tomography at the tenth day after onset or subsequently. Serial studies disclosed atrophic changes in the frontal lobes. All patients manifested regression or retardation of motor and verbal functions. The recovery of intellectual deficit was slower and less prominent than that of motor dysfunction. These unique features suggest that the frontal lobes are the focus of this novel subtype of acute encephalopathy, which we propose to call acute infantile encephalopathy predominantly affecting the frontal lobes.

Social cognition and epilepsy surgery

Human social behavior depends on a set of perceptive, mnemonic, and interpretive abilities that together may be termed social cognition. Lesion and functional imaging studies of social cognitive functions implicate the temporal lobes (in particular, the nondominant temporal lobe) and mesial temporal structures as critical at the front end of social cognitive processes. The frontal lobes, in turn, function to interpret and to modulate these processes via top-down control. Damage to frontal regions is associated with specific derangements in social behavior. Chronic focal-onset epilepsy and its surgical treatment commonly affect these neuroanatomic regions and might therefore impact social function. Postoperative social function helps determine quality of life for both patients and families. There is some evidence that resective seizure surgery affects social cognition, but there are significant weaknesses in our current knowledge that can be overcome with comprehensive longitudinal research.

Emotion, motivation, and the brain: Reflex foundations in animal and human research

This review will focus on a motivational circuit in the brain, centered on the amygdala, that underlies human emotion. This neural circuitry of appetitive/approach and defensive/avoidance was laid down early in our evolutionary history in primitive cortex, sub-cortex, and mid-brain, to mediate behaviors basic to the survival of individuals and the propagation of genes to coming generations. Thus, events associated with appetitive rewards, or that threaten danger or pain, engage attention and prompt information gathering more so than other input. Motive cues also occasion metabolic arousal, anticipatory responses, and mobilize the organism to prepare for action. Findings are presented from research with animals, elucidating these psychophysiological (e.g., cardiovascular, neuro-humoral) and behavioral (e.g., startle potentiation, "freezing") patterns in emotion, and defining their mediating brain circuits. Parallel results are described from experiments with humans, showing similar activation patterns in brain and body in response to emotion cues, co-varying with participants' reports of affective valence and increasing emotional arousal.

Assessment of hot and cool executive function in young children: age-related changes and individual differences

Although executive function (EF) is often considered a domain-general cognitive function, a distinction has been made between the "cool" cognitive aspects of EF more associated with dorsolateral regions of prefrontal cortex and the "hot" affective aspects more associated with ventral and medial regions (Zelazo and Mller, 2002). Assessments of EF in children have focused almost exclusively on cool EF. In this study, EF was assessed in 3- to 5-year-old children using 2 putative measures of cool EF (Self-Ordered Pointing and Dimensional Change Card Sort) and 2 putative measures of hot EF (Children's Gambling Task and Delay of Gratification). Findings confirmed that performance on both types of task develops during the preschool period. However, the measures of hot and cool EF showed different patterns of relations with each other and with measures of general intellectual function and temperament. These differences provide preliminary evidence that hot and cool EF are indeed distinct, and they encourage further research on the development of hot EF.

Correspondence of cue activity to reward activity in the macaque orbitofrontal cortex

It has been reported that neurons in the orbitofrontal cortex (OFC) respond to emotionally significant events such as reward-predicting cues and/or the reward itself. The responses to reward-predicting cues are considered to carry the information of the predicted reward. However, few studies have focused on the relationship of the neuronal activity during a cue period with that during a reward period. We can infer that the cue responses of OFC neurons are correlated to the reward responses if they carry the information of the predicted reward. In this study, we focused on neurons that showed responses during both the cue and reward periods, and compared the response characteristics between these periods. We found 94 of 369 OFC neurons showed significant responses during both the cue and reward periods, and 43 of which preserved their selectivity between these periods. Furthermore, population analysis showed that stronger cue responses corresponded to stronger reward responses, and stronger reward responses corresponded to stronger cue responses. These results suggest that individual neurons in the OFC associate visual information with reward information, and contribute to the prediction of future rewards by forming reward representations.

Reduced anterior and posterior cingulate gray matter in borderline personality disorder

BACKGROUND

Structural abnormalities in prefrontal and cingulate gyrus regions-important in affective processing, impulse control and cognition may contribute to the psychopathology of borderline personality disorder (BPD). Previous MRI studies examining volume have reported that compared with healthy controls, BPD patients have decreases in right anterior cingulate, no differences in dorsolateral prefrontal cortex, and mixed findings for prefrontal cortex. We extended this investigation by examining gray and white matter volume of frontal and cingulate gyrus Brodmann areas (BAs) in a large group of patients and healthy controls.

METHODS

MRI scans were acquired in 50 BPD patients (n = 13 with comorbid diagnosis of BPD and Schizotypal Personality Disorder (SPD) and n = 37 without SPD) and 50 healthy controls, and gray/white matter volume in cingulate gyrus and frontal lobe BAs were assessed. Normal BPD and BPD subgroup comparisons were conducted.

RESULTS

Compared with controls, BPD patients showed reduced gray matter volume in BA 24 and 31 of the cingulate. BPD patients without comorbid SPD had isolated gray matter volume loss in BA 24, but were spared for BA 31 in contrast to BPD patients with SPD. There were no group differences in whole cingulate or frontal lobe volume.

CONCLUSIONS

The finding of more pervasive cingulate shrinkage in the patients with BPD and SPD comorbidity resembles recent observations with the same methods in patients with schizophrenia. The pattern of reduced anterior and posterior cingulate gray matter volume in BPD patients, particularly those comorbid for SPD is consistent with the affective and attentional deficits observed in these personality disorders.

Acquired sociopathy and frontotemporal dementia

BACKGROUND

It is not understood why some patients with frontotemporal dementia (FTD) manifest sociopathic behavior.

OBJECTIVE

To examine the prevalence and characteristics of sociopathic behavior in FTD patients as compared to those with Alzheimer's disease (AD).

METHODS AND PARTICIPANTS

We surveyed a group of FTD patients and a group of AD patients for sociopathic behavior, evaluated the characteristics surrounding their acts, and compared the groups on neuropsychological tests and functional neuroimaging. Twenty-eight outpatients with FTD (15 men, 13 women; 61.9+/-7.1 years; Mini-Mental State Examination score 23.6+/-8.1) were compared with 28 patients with clinically probable AD (13 men, 15 women; 66.1+/-9.2 years; Mini-Mental State Examination score 21.3 +/- 5.3). Main outcome measures included: (a) the prevalence of sociopathic acts; (b) a structured interview; (c) neuropsychological tests including the Frontal Assessment Battery, and (d) clinically obtained positron emission tomography or single photon emission tomography scans.

RESULTS

Sixteen (57%) of the FTD patients had sociopathic behavior compared to two (7%) of the AD patients (chi(2)=13.84, p<0.001). Sociopathic acts among FTD patients included unsolicited sexual acts, traffic violations, physical assaults, and other unacceptable behaviors. On interview, the FTD patients with sociopathic acts were aware of their behavior and knew that it was wrong but could not prevent themselves from acting impulsively. They claimed subsequent remorse, but they did not act on it or show concern for the consequences. Among FTD patients with sociopathy, neuropsychological assessment showed impaired motor inhibition, and functional neuroimaging showed right frontotemporal involvement.

CONCLUSION

The results suggest that sociopathy in FTD results from a combination of diminished emotional concern for the consequences of their acts and disinhibition consequent to right frontotemporal dysfunction. In many jurisdictions, FTD patients with sociopathy would not pass legal criteria for 'not guilty by reason of insanity'.

The role of spatial frequency information for ERP components sensitive to faces and emotional facial expression

To investigate the impact of spatial frequency on emotional facial expression analysis, ERPs were recorded in response to low spatial frequency (LSF), high spatial frequency (HSF), and unfiltered broad spatial frequency (BSF) faces with fearful or neutral expressions, houses, and chairs. In line with previous findings, BSF fearful facial expressions elicited a greater frontal positivity than BSF neutral facial expressions, starting at about 150 ms after stimulus onset. In contrast, this emotional expression effect was absent for HSF and LSF faces. Given that some brain regions involved in emotion processing, such as amygdala and connected structures, are selectively tuned to LSF visual inputs, these data suggest that ERP effects of emotional facial expression do not directly reflect activity in these regions. It is argued that higher order neocortical brain systems are involved in the generation of emotion-specific waveform modulations. The face-sensitive N170 component was neither affected by emotional facial expression nor by spatial frequency information.

Dendritic computation

One of the central questions in neuroscience is how particular tasks, or computations, are implemented by neural networks to generate behavior. The prevailing view has been that information processing in neural networks results primarily from the properties of synapses and the connectivity of neurons within the network, with the intrinsic excitability of single neurons playing a lesser role. As a consequence, the contribution of single neurons to computation in the brain has long been underestimated. Here we review recent work showing that neuronal dendrites exhibit a range of linear and nonlinear mechanisms that allow them to implement elementary computations. We discuss why these dendritic properties may be essential for the computations performed by the neuron and the network and provide theoretical and experimental examples to support this view.

Responding to the emotions of others: dissociating forms of empathy through the study of typical and psychiatric populations

Empathy is a lay term that is becoming increasingly viewed as a unitary function within the field of cognitive neuroscience. In this paper, a selective review of the empathy literature is provided. It is argued from this literature that empathy is not a unitary system but rather a loose collection of partially dissociable neurocognitive systems. In particular, three main divisions can be made: cognitive empathy (or Theory of Mind), motor empathy, and emotional empathy. The two main psychiatric disorders associated with empathic dysfunction are considered: autism and psychopathy. It is argued that individuals with autism show difficulties with cognitive and motor empathy but less clear difficulties with respect to emotional empathy. In contrast, individuals with psychopathy show clear difficulties with a specific form of emotional empathy but no indications of impairment with cognitive and motor empathy.

The orbitofrontal-amygdala circuit and self-regulation of social-emotional behavior in autism

Individuals with an autistic spectrum disorder are impaired not only in understanding others' mental states, but also in self-regulation of social-emotional behavior. Therefore, a model of the brain in autism must encompass not only those brain systems that subserve social-cognitive and emotional functioning, but also those that subserve the self-regulation of behavior in response to a changing social environment. We present evidence to support the hypothesis that developmental dysfunction of the orbitofrontal-amygdala circuit of the brain is a critical factor in the development of autism and that some of the characteristic deficits of persons with autism in socio-emotional cognition and behavioral self-regulation are related to early dysfunction of different components of this circuit. A secondary hypothesis posits that the degree of intellectual impairment present in individuals with autism is directly related to the integrity of the dorsolateral prefrontal-hippocampal circuit of the brain. Together, these hypotheses have the potential to help explain the neurodevelopmental basis of some of the primary manifestations of autism as well as the heterogeneity of outcomes.

Lateralization of the frontal lobe functions elicited by a cognitive bias task is a fundamental process. Lesion study

Cognitive neuroscience researchers have hypothesized that context-dependent and context-independent response selection is associated with the left and right frontal lobe, respectively, in right-handed adult males. Patients with left frontal lobe lesions show context-independent reasoning in a cognitive bias task (CBT), while those with right frontal lesions show context-dependent reasoning. Young children show more context-independent responses in a modified CBT (mCBT), while adolescents and adults show more context-dependent responses. We investigated the cognitive bias of right-handed children with unilateral frontal lobe lesions/epileptic foci to explore the plasticity of lateralization in the frontal lobes. The study included eight children with left frontal lobe lesions/epileptic foci (LLF) and four children with right frontal lobe lesions/epileptic foci (RLF). Twenty-three right-handed age-matched males served as controls. A computer presented version of the original card-choice task that was simplified and modified for children was used (mCBT). Simple visual stimuli differed dichotomously in shape, color, number, and shading. A target object presented alone was followed by two choices from which subjects made selection based on preference. Considering all four characteristics, the degree of similarity between the target and the subjects' choice was scored for 30 trials. A high score indicated a context-dependent response selection bias and a low score indicated a context-independent bias. The RLF subjects had a higher converted score (mean: 26.8+/-2.2), while LLF subjects showed a lower converted score (mean: 7.75+/-6.3). There were highly significant differences between LLF subjects and the other groups (P<0.001 vs. controls or RLF subjects). No significant correlations were observed between the converted scores and the age at onset, time since insult, or IQ in either LLF or RLF subjects. These findings suggest that the lateralization of frontal lobe function elicited by mCBT is fundamental and independent of language lateralization, rather than secondary to it. Furthermore, these findings also indicate that the timetable for the development of lateralized frontal lobe functions depends upon biologic factors.

Executive functions after traumatic brain injury in children

There is growing recognition that executive function, the superordinate, managerial capacity for directing more modular abilities, is frequently impaired by traumatic brain injury in children and mediates the neurobehavioral sequelae exhibited by these patients. This review encompasses the definition of specific executive functions, age-related changes in executive functions in typically developing children, and the effects of traumatic brain injury on executive functions. The neural substrate for executive functions is described, including relevant functional brain imaging studies that have implicated mediation by prefrontal and parietal cortex and their circuitry. The vulnerability of the neural substrate for executive function to the pathophysiology of traumatic brain injury is discussed, including focal lesions and diffuse axonal injury. Domains of executive functions covered in this review include the basic processes of working memory and inhibition and more complex processes such as decision making. Other domains of executive function, including motivation, self-regulation, and social cognition are discussed in terms of research methodology, clinical assessment, and findings in children with traumatic brain injury. Proposed approaches to the rehabilitation of executive functions are presented.

Mapping brain maturation and cognitive development during adolescence

Non-invasive mapping of brain structure and function with magnetic resonance imaging (MRI) has opened up unprecedented opportunities for studying the neural substrates underlying cognitive development. There is an emerging consensus of a continuous increase throughout adolescence in the volume of white matter, both global and local. There is less agreement on the meaning of asynchronous age-related decreases in the volume of grey matter in different cortical regions; these might equally represent loss ("pruning") or gain (intra-cortical myelination) of tissue. Functional MRI studies have so far focused mostly on executive functions, such as working memory and behavioural inhibition, with very few addressing questions regarding the maturation of social cognition. Future directions for research in this area are discussed in the context of processing biological motion and matching perceptions and actions.

Neurobiology of executive functions: catecholamine influences on prefrontal cortical functions

The prefrontal cortex guides behaviors, thoughts, and feelings using representational knowledge, i.e., working memory. These fundamental cognitive abilities subserve the so-called executive functions: the ability to inhibit inappropriate behaviors and thoughts, regulate our attention, monitor our actions, and plan and organize for the future. Neuropsychological and imaging studies indicate that these prefrontal cortex functions are weaker in patients with attention-deficit/hyperactivity disorder and contribute substantially to attention-deficit/hyperactivity disorder symptomology. Research in animals indicates that the prefrontal cortex is very sensitive to its neurochemical environment and that small changes in catecholamine modulation of prefrontal cortex cells can have profound effects on the ability of the prefrontal cortex to guide behavior. Optimal levels of norepinephrine acting at postsynaptic alpha-2A-adrenoceptors and dopamine acting at D1 receptors are essential to prefrontal cortex function. Blockade of norepinephrine alpha-2-adrenoceptors in prefrontal cortex markedly impairs prefrontal cortex function and mimics most of the symptoms of attention-deficit/hyperactivity disorder, including impulsivity and locomotor hyperactivity. Conversely, stimulation of alpha-2-adrenoceptors in prefrontal cortex strengthens prefrontal cortex regulation of behavior and reduces distractibility. Most effective treatments for attention-deficit/hyperactivity disorder facilitate catecholamine transmission and likely have their therapeutic actions by optimizing catecholamine actions in prefrontal cortex.

Emotional and Temporal Aspects of Situation Model Processing during Text Comprehension: An Event-Related fMRI Study

Language comprehension in everyday life requires the continuous integration of prior discourse context and general world knowledge with the current utterance or sentence. In the neurolinguistic literature, these so-called situation model building processes have been ascribed to the prefrontal cortex or to the right hemisphere. In this study, we use whole-head event-related fMRI to directly map the neural correlates of narrative comprehension in context. While being scanned using a spin-echo sequence, 20 participants listened to 32 short stories, half of which contained globally inconsistent information. The inconsistencies concerned either temporal or chronological information or the emotional status of the protagonist. Hearing an inconsistent word elicited activation in the right anterior temporal lobe. The comparison of different information aspects revealed activation in the left precuneus and a bilateral frontoparietal network for chronological information. Emotional information elicited activation in the ventromedial prefrontal cortex and the extended amygdaloid complex. In addition, the integration of inconsistent emotional information engaged the dorsal frontomedial cortex (Brodmann's area 8/9), whereas the integration of inconsistent temporal information required the lateral prefrontal cortex bilaterally. These results indicate that listening to stories can elicit activation reflecting content-specific processes. Furthermore, updating of the situation model is not a unitary process but it also depends on the particular requirements of the text. The right hemisphere contributes to language processing in context, but equally important are the left medial and bilateral prefrontal cortices.

Dominance attributions following damage to the ventromedial prefrontal cortex

Damage to the human ventromedial prefrontal cortex (VM) can result in dramatic and maladaptive changes in social behavior despite preservation of most other cognitive abilities. One important aspect of social cognition is the ability to detect social dominance, a process of attributing from particular social signals another person's relative standing in the social world. To test the role of the VM in making attributions of social dominance, we designed two experiments: one requiring dominance judgments from static pictures of faces, the second requiring dominance judgments from film clips. We tested three demographically matched groups of subjects: subjects with focal lesions in the VM (n = 15), brain-damaged comparison subjects with lesions excluding the VM (n = 11), and a reference group of normal individuals with no history of neurological disease (n = 32). Contrary to our expectation, we found that subjects with VM lesions gave dominance judgments on both tasks that did not differ significantly from those given by the other groups. Despite their grossly normal performance, however, subjects with VM lesions showed more subtle impairments specifically when judging static faces: They were less discriminative in their dominance judgments, and did not appear to make normal use of gender and age of the faces in forming their judgments. The findings suggest that, in the laboratory tasks we used, damage to the VM does not necessarily impair judgments of social dominance, although it appears to result in alterations in strategy that might translate into behavioral impairments in real life.

Seeing it my way: a case of a selective deficit in inhibiting self-perspective

Little is known about the functional and neural architecture of social reasoning, one major obstacle being that we crucially lack the relevant tools to test potentially different social reasoning components. In the case of belief reasoning, previous studies have tried to separate the processes involved in belief reasoning per se from those involved in the processing of the high incidental demands such as the working memory demands of typical belief tasks. In this study, we developed new belief tasks in order to disentangle, for the first time, two perspective taking components involved in belief reasoning: (i) the ability to inhibit one's own perspective (self-perspective inhibition); and (ii) the ability to infer someone else's perspective as such (other-perspective taking). The two tasks had similar demands in other-perspective taking as they both required the participant to infer that a character has a false belief about an object's location. However, the tasks varied in the self-perspective inhibition demands. In the task with the lowest self-perspective inhibition demands, at the time the participant had to infer the character's false belief, he or she had no idea what the new object's location was. In contrast, in the task with the highest self-perspective inhibition demands, at the time the participant had to infer the character's false belief, he or she knew where the object was actually located (and this knowledge had thus to be inhibited). The two tasks were presented to a stroke patient, WBA, with right prefrontal and temporal damage. WBA performed well in the low-inhibition false-belief task but showed striking difficulty in the task placing high self-perspective inhibition demands, showing a selective deficit in inhibiting self-perspective. WBA also made egocentric errors in other social and visual perspective taking tasks, indicating a difficulty with belief attribution extending to the attribution of emotions, desires and visual experiences to other people. The case of WBA, together with the recent report of three patients impaired in belief reasoning even when self-perspective inhibition demands were reduced, provide the first neuropsychological evidence that the inhibition of one's own point of view and the ability to infer someone else's point of view rely on distinct neural and functional processes.

Direction selectivity of excitation and inhibition in simple cells of the cat primary visual cortex

Direction selectivity in simple cells of primary visual cortex, defined from their spike responses, cannot be predicted using linear models. It has been suggested that the shunting inhibition evoked by visual stimulation is responsible for the nonlinear component of direction selectivity. Cortical inhibition would suppress a neuron's firing when stimuli move in the nonpreferred direction, but would allow responses to stimuli in the preferred direction. Models of direction selectivity based solely on input from the lateral geniculate nucleus, however, propose that the nonlinear response is caused by spike threshold. By extracting excitatory and inhibitory components of synaptic inputs from intracellular records obtained in vivo, we demonstrate that excitation and inhibition are tuned for the same direction, but differ in relative timing. Further, membrane potential responses combine in a linear fashion. Spike threshold, however, quantitatively accounts for the nonlinear component of direction selectivity, amplifying the direction selectivity of spike output relative to that of synaptic inputs.

The brain, aggression, and public policy

Investigational, conceptual, and interventional advances in the neurosciences strain consensus in research ethics, clinical ethics, legal ethics, and jurisprudence and demand innovative adaptation in public policy. I review these advances, ask how they might change a range of policies, and conclude that their implications -- particularly relating to aggression -- are likely to have been underestimated.

Relation between the prefrontal cortex and cerebro-cerebellar functions: evidence from the results of stabilometrical indexes

The relation between prefrontal cortex and cerebro-cerebellar functions of 50 normal healthy elderly people was examined. The function of the prefrontal cortex was measured by means of a letter fluency test and the Digit Cancellation Test (D-CAT, a test for the assessment of attention). Two indexes of postural tremor measured by the stabilometer were employed for the indication of cerebello-thalamo-cortical circuit functions. The results of groups consisting of participants showing higher or lower scores than the mean of the norm on the stabilometer index measurements were compared with their D-CAT and letter fluency test performances. The results showed that 2 indexes of cerebello-thalamo-cortical circuit functions related to the attention function while the relation to the language function was rather weak. The results of the behavioral measures demonstrated a mutual relation between prefrontal cortex and cerebello-thalamo-cortical circuit functions and strongly suggest the notion that the human brain functions as a system, which includes neocortex, subcortex, and cerebellum.

Artificial time constraints on the Iowa Gambling Task: The effects on behavioural performance and subjective experience

In the last decade, the Iowa Gambling Task (IGT) has become a widely employed neuropsychological research instrument for the investigation of executive function. The task has been employed in a wide range of formats, from 'manual' procedures to more recently introduced computerised versions. Computer-based formats often require that responses on the task should be artificially delayed by a number of seconds between trials to collect skin-conductance data. Participants, however, may become frustrated when they want to select from a particular deck in the time-limited versions--so that an unintended emotional experience of frustration might well disrupt a task presumed to be reliant on emotion-based learning. We investigated the effect of the various types of Iowa Gambling Task format on performance, using three types of task: the classic manual administration, with no time limitations; a computerised administration with a 6-s enforced delay; and a control computerised version which had no time constraints. We also evaluated the subjective experience of participants on each task. There were no significant differences in performance, between formats, in behavioural terms. Subjective experience measures on the task also showed consistent effects across all three formats-with substantial, and rapidly developing, awareness of which decks were 'good' and 'bad.'

Influence of bodily harm on neural correlates of semantic and moral decision-making

Moral decision-making is central to everyday social life because the evaluation of the actions of another agent or our own actions made with respect to the norms and values guides our behavior in a community. There is previous evidence that the presence of bodily harm--even if irrelevant for a decision--may affect the decision-making process. While recent neuroimaging studies found a common neural substrate of moral decision-making, the role of bodily harm has not been systematically studied so far. Here we used event-related functional magnetic resonance imaging (fMRI) to investigate how behavioral and neural correlates of semantic and moral decision-making processes are modulated by the presence of direct bodily harm or violence in the stimuli. Twelve participants made moral and semantic decisions about sentences describing actions of agents that either contained bodily harm or not and that could easily be judged as being good or bad or correct/incorrect, respectively. During moral and semantic decision-making, the presence of bodily harm resulted in faster response times (RT) and weaker activity in the temporal poles relative to trials devoid of bodily harm/violence, indicating a processing advantage and reduced processing depth for violence-related linguistic stimuli. Notably, there was no increase in activity in the amygdala and the posterior cingulate cortex (PCC) in response to trials containing bodily harm. These findings might be a correlate of limited generation of the semantic and emotional context in the anterior temporal poles during the evaluation of actions of another agent related to violence that is made with respect to the norms and values guiding our behavior in a community.

Neural correlates of semantic and behavioural deficits in frontotemporal dementia

Patients with frontotemporal dementia (FTD) can present with the clinical syndrome of semantic dementia due to a progressive loss of semantic knowledge or a neuropsychiatric syndrome characterised by aberrant social behaviours although frequently both co-exist. It has been assumed that the former is underpinned by damage to the temporal lobes and the latter, predominantly, by damage to the frontal lobes. Using the technique of voxel-based morphometry, we studied a group of FTD cases (n = 18) with a range of cognitive and neuropsychiatric features to correlate loss of semantic knowledge (as measured by the sum of two semantic tests) and aberrant behaviour (as measured by the neuropsychiatric inventory, NPI) with regional loss of grey matter volume. Semantic breakdown correlated with extensive loss of grey matter volume throughout the left anterior temporal lobe and less significantly with right temporal pole and subcallosal gyrus. Aberrant behaviour correlated with loss of grey matter volume in the dorso-mesial frontal lobe--paracingulate region, Brodmann areas 6/8/9--more so on the right. The frontal paracingulate correlation suggests that damage to this region may significantly contribute to the genesis of the behavioural syndrome seen in FTD.

The functional architecture of human empathy

Empathy accounts for the naturally occurring subjective experience of similarity between the feelings expressed by self and others without loosing sight of whose feelings belong to whom. Empathy involves not only the affective experience of the other person's actual or inferred emotional state but also some minimal recognition and understanding of another's emotional state. In light of multiple levels of analysis ranging from developmental psychology, social psychology, cognitive neuroscience, and clinical neuropsychology, this article proposes a model of empathy that involves parallel and distributed processing in a number of dissociable computational mechanisms. Shared neural representations, self-awareness, mental flexibility, and emotion regulation constitute the basic macrocomponents of empathy, which are underpinned by specific neural systems. This functional model may be used to make specific predictions about the various empathy deficits that can be encountered in different forms of social and neurological disorders.

Brain activation associated with evaluative processes of guilt and embarrassment: an fMRI study

We aimed to investigate the neural substrates associated with evaluative process of moral emotions. Using functional magnetic resonance imaging (fMRI), we examined the similarities and differences between evaluative process of guilt and that of embarrassment at the neural basis level. Study of the neural basis of judgments of moral emotions might contribute to a better understanding of the amoral behavior observed in neurological and psychiatric disorders. Nineteen healthy volunteers were studied. The participants read sentences carrying neutral, guilty, or embarrassing contents during the scans. Both guilt and embarrassment conditions commonly activated the medial prefrontal cortex (MPFC), left posterior superior temporal sulcus (STS), and visual cortex. Compared to guilt condition, embarrassment condition produced greater activation in the right temporal cortex (anterior), bilateral hippocampus, and visual cortex. Most of these regions have been implicated in the neural substrate of social cognition or Theory of Mind (ToM). Our results support the idea that both are self-conscious emotions, which are social emotions requiring the ability to represent the mental states of others. At the same time, our functional fMRI data are in favor of the notion that evaluative process of embarrassment might be a more complex process than that of guilt.

Multiplication and stimulus invariance in a looming-sensitive neuron

Multiplicative operations and invariance of neuronal responses are thought to play important roles in the processing of neural information in many sensory systems. Yet the biophysical mechanisms that underlie both multiplication and invariance of neuronal responses in vivo, either at the single cell or at the network level, remain to a large extent unknown. Recent work on an identified neuron in the locust visual system (the LGMD neuron) that responds well to objects looming on a collision course towards the animal suggests that this cell represents a good model to investigate the biophysical basis of multiplication and invariance at the single neuron level. Experimental and theoretical results are consistent with multiplication being implemented by subtraction of two logarithmic terms followed by exponentiation via active membrane conductances, according to a x 1/b = exp(log(a) - log(b)). Invariance appears to be in part due to non-linear integration of synaptic inputs within the dendritic tree of this neuron.

Abnormal neural responses to emotional visual stimuli in adolescents with conduct disorder

BACKGROUND

It is widely held that aggression and antisocial behavior arise as a consequence of a deficiency in responding to emotional cues in the social environment. We asked whether neural responses evoked by affect-laden pictures would be abnormal in adolescents with conduct disorder (CD).

METHODS

Functional magnetic resonance imaging during passive viewing of pictures with neutral or strong negative affective valence was performed in 13 male adolescents with severe CD aged 9 to 15 years and in 14 healthy age-matched control subjects.

RESULTS

Main effects for negative-neutral affective valence included activations in the amygdala and hippocampus, ventral extrastriate visual cortex, and intraparietal sulcus bilaterally. There was a significant group-by-condition interaction in the right dorsal anterior cingulate cortex that was due to a pronounced deactivation in the patient group during viewing of negative pictures. When correcting for anxiety and depressive symptoms, we additionally found a reduced responsiveness of the left amygdala to negative pictures in patients compared with control subjects.

CONCLUSIONS

We suggest that these findings reflect an impairment of both the recognition of emotional stimuli and the cognitive control of emotional behavior in patients with CD, resulting in a propensity for aggressive behavior.

Social cognitive neuroscience: where are we heading?

Humans crave the company of others and suffer profoundly if temporarily isolated from society. Much of the brain must have evolved to deal with social communication and we are increasingly learning more about the neurophysiological basis of social cognition. Here, we explore some of the reasons why social cognitive neuroscience is captivating the interest of many researchers. We focus on its future, and what we believe are priority areas for further research.

Neuronal circuits of the neocortex

We explore the extent to which neocortical circuits generalize, i.e., to what extent can neocortical neurons and the circuits they form be considered as canonical? We find that, as has long been suspected by cortical neuroanatomists, the same basic laminar and tangential organization of the excitatory neurons of the neocortex is evident wherever it has been sought. Similarly, the inhibitory neurons show characteristic morphology and patterns of connections throughout the neocortex. We offer a simple model of cortical processing that is consistent with the major features of cortical circuits: The superficial layer neurons within local patches of cortex, and within areas, cooperate to explore all possible interpretations of different cortical input and cooperatively select an interpretation consistent with their various cortical and subcortical inputs.

Functional differences among those high and low on a trait measure of psychopathy

BACKGROUND

It has been established that individuals who score high on measures of psychopathy demonstrate difficulty when performing tasks requiring the interpretation of other's emotional states. The aim of this study was to elucidate the relation of emotion and cognition to individual differences on a standard psychopathy personality inventory (PPI) among a nonpsychiatric population.

METHODS

Twenty participants completed the PPI. Following survey completion, a mean split of their scores on the emotional-interpersonal factor was performed, and participants were placed into a high or low group. Functional magnetic resonance imaging data were collected while participants performed a recognition task that required attention be given to either the affect or identity of target stimuli.

RESULTS

No significant behavioral differences were found. In response to the affect recognition task, significant differences between high- and low-scoring subjects were observed in several subregions of the frontal cortex, as well as the amygdala. No significant differences were found between the groups in response to the identity recognition condition.

CONCLUSIONS

Results indicate that participants scoring high on the PPI, although not behaviorally distinct, demonstrate a significantly different pattern of neural activity (as measured by blood oxygen level-dependent contrast)in response to tasks that require affective processing. The results suggest a unique neural signature associated with personality differences in a nonpsychiatric population.