'Theory of mind' in the brain. Evidence from a PET scan study of Asperger syndrome

Annotation: the neural basis of social impairments in autism: the role of the dorsal medial-frontal cortex and anterior cingulate system

BACKGROUND

The fundamental social disturbance of autism is characterized, in part, by problems in the acquisition of joint attention skills in the first years of life, followed by impairments in the development of social cognition, as assessed on theory of mind (ToM) measures. Recently, studies have indicated that a system involving the dorsal medial-frontal cortex (DMFC), and the anterior cingulate (AC), may contribute to the development of the tendency to initiate joint attention in infancy. Similarly, research has implicated the DMFC/AC system in ToM performance in typical and atypical individuals. These data suggest it may be useful to consider the functions associated with this system in the developmental psychopathology of autism.

METHOD

A review of the studies of the connections between the DMFC/AC system, joint attention and ToM task performance.

RESULTS AND CONCLUSIONS

This review raises the hypothesis that the DMFC/AC may be involved in the basic disturbance in social orienting in autism. The DMFAC/AC may also play a role in the capacity to monitor proprioceptive information concerning self-action and integrate this self-related information with exteroceptive perceptual information about the behavior of other people. A disturbance in these functions of the DMFC/ AC may contribute to the atypical development of intersubjectivity, joint attention and social cognition that may impair the lives of people with autism. Thus, impairment in the development of this system may constitute a neural substrate for socio-cognitive deficits in autism.

A neurobiological mapping of theory of mind

This paper attempts, based on a review of a wide range of clinical, biobehavioral and neuroanatomical studies, to account for the various theory of mind impairments observed in psychiatric and developmental disorders in a single neurobiological model. The proposed model is composed of a representational component subserved by posterior brain regions (temporal and parietal) and an application/execution component subserved by prefrontal regions. Information processed in posterior regions is relayed through a limbic-paralimbic system, which is essential for the implementation of theory of mind processes. In addition to its clinical implications, the proposed model accounts for (1) the ability to mentalize about both the self and others, (2) the nature of the anatomic connections of the various brain regions and their functional correlates, and (3) theories pertaining to the inferencing mechanisms used during mental representation/attribution.

"Hey John": signals conveying communicative intention toward the self activate brain regions associated with "mentalizing," regardless of modality

Successful communication between two people depends first on the recognition of the intention to communicate. Such intentions may be conveyed by signals directed at the self, such as calling a person's name or making eye contact. In this study we use functional magnetic resonance imaging to show that the perception of these two signals, which differ in modality and sensory channel, activate common brain regions: the paracingulate cortex and temporal poles bilaterally. These regions are part of a network that has been consistently activated when people are asked to think about the mental states of others. Activation of this network is independent of arousal as measured by changes in pupil diameter.

Social neuroscience, empathy, brain integration, and neurodevelopmental disorders

Paul MacLean has investigated integrated brain functioning through selected brain lesions in animals that disturb circuits necessary for complex behaviors, such as social displays. MacLean is unique in his comparative neurobehavioral approach that emphasizes the evolutionary origins of parenting and social behaviors and the implications of brain changes in the evolution from reptiles (social displays) to mammals (nursing, audiovocal communication, play) to man (self-awareness, intentionality, social context) that link affect and cognition. Subjectively, how "looking with feeling toward others," the basic element in empathy, evolved has been a central concern of his. Neuroimaging studies of social cognition, mother-infant communication, moral behavior, forgiveness, and trust are consistent with particular brain systems being activated in cooperative social behaviors. The identification of mirror neurons is pertinent to MacLean's model of isopraxis and studies of thalamocortical resonances may be pertinent to his neurobehavioral models. Studies of behavioral phenotypes in human neurodevelopmental disorders are consistent with MacLean's model of brain circuits being linked to complex behaviors during development. In autistic disorder, the behavioral phenotype involves disrupted social communication, deviant imaginative play, and motor stereotypies. In Lesch-Nyhan syndrome (LNS), self-injury occurs in individuals with normal sensory systems intact who require and request physical restraint to prevent self-injury; they ask for assistance from others to prevent them from harming themselves. Autism involves the lack of subjective awareness of others intentions and LNS involves a failure in self-regulation and self-control of self-injurious behavior. MacLean's models laid the groundwork for studies focused on understanding brain functioning in these conditions.

Mentalizing

Mentalizing, the process of making sense of mental states in oneself and other persons, plays a central role in psychopathology and psychotherapy. The author explicates the concept of mentalizing, highlights some factors critical to its development, and illustrates its clinical applications in the domains of trauma and depression.

Social cognition in frontotemporal dementia and Huntington's disease

Frontotemporal dementia (FTD) and Huntington's disease (HD) are degenerative disorders, with predominant involvement, respectively of frontal neocortex and striatum. Both conditions give rise to altered social conduct and breakdown in interpersonal relationships, although the factors underlying these changes remain poorly defined. The study used tests of theory of mind (interpretation of cartoons and stories and judgement of preference based on eye gaze) to explore the ability of patients with FTD and HD to interpret social situations and ascribe mental states to others. Performance in the FTD group was severely impaired on all tasks, regardless of whether the test condition required attribution of a mental state. The HD group showed a milder impairment in cartoon and story interpretation, and normal preference judgements. Qualitative differences in performance were demonstrated between groups. FTD patients made more concrete, literal interpretations, whereas HD patients were more likely to misconstrue situations. The findings are interpreted as demonstrating impaired theory of mind in FTD, as one component of widespread executive deficits. In HD the evidence does not suggest a fundamental loss of theory of mind, but rather a tendency to draw faulty inferences from social situations. It is concluded that social breakdown in FTD and HD may have a different underlying basis and that the frontal neocortex and striatum have distinct contributions to social behaviour.

Being the target of another's emotion: a PET study

The eye region and gaze behaviour are known to play a major role in conveying information about direction of attention and emotional dispositions. Positron emission tomography scanning was used to explore the cerebral structures involved while subjects were asked to attribute hostile or friendly intentions to video-taped actors who directed attention towards or away from the subjects. As expected, a number of brain regions known to be involved in emotion processing was found activated when subjects had to attribute an emotion regardless of gaze direction. In addition, results indicate that gaze direction has an impact on the brain regions recruited to interpret emotions. The anterior region of the superior temporal gyrus (STG) was selectively activated during analysis of emotions through eye contact. This result provides neurophysiological evidence for privileged processing when an individual becomes personally involved as the object of another's emotions.

Understanding autism: insights from mind and brain

Autism is a developmental disorder characterized by impaired social interaction and communication as well as repetitive behaviours and restricted interests. The consequences of this disorder for everyday life adaptation are extremely variable. The general public is now more aware of the high prevalence of this lifelong disorder, with ca. 0.6% of the population being affected. However, the signs and symptoms of autism are still puzzling. Since a biological basis of autism was accepted, approaches from developmental cognitive neuroscience have been applied to further our understanding of the autism spectrum. The study of the behavioural and underlying cognitive deficits in autism has advanced ahead of the study of the underlying brain abnormalities and of the putative genetic mechanisms. However, advances in these fields are expected as methodological difficulties are overcome. In this paper, recent developments in the field of autism are outlined. In particular, we review the findings of the three main neuro-cognitive theories of autism: theory-of-mind deficit, weak central coherence and executive dysfunction.

The role of the fusiform face area in social cognition: implications for the pathobiology of autism

A region in the lateral aspect of the fusiform gyrus (FG) is more engaged by human faces than any other category of image. It has come to be known as the 'fusiform face area' (FFA). The origin and extent of this specialization is currently a topic of great interest and debate. This is of special relevance to autism, because recent studies have shown that the FFA is hypoactive to faces in this disorder. In two linked functional magnetic resonance imaging (fMRI) studies of healthy young adults, we show here that the FFA is engaged by a social attribution task (SAT) involving perception of human-like interactions among three simple geometric shapes. The amygdala, temporal pole, medial prefrontal cortex, inferolateral frontal cortex and superior temporal sulci were also significantly engaged. Activation of the FFA to a task without faces challenges the received view that the FFA is restricted in its activities to the perception of faces. We speculate that abstract semantic information associated with faces is encoded in the FG region and retrieved for social computations. From this perspective, the literature on hypoactivation of the FFA in autism may be interpreted as a reflection of a core social cognitive mechanism underlying the disorder.

Neural correlates of the first-person-perspective

Human self-consciousness depends on the metarepresentation of mental and bodily states as one's own mental and bodily states. First-person-perspective taking is not sufficient, but necessary for human self-consciousness. To assign a first-person-perspective is to center one's own multimodal experiential space upon one's own body, thus operating in an egocentric reference frame. The brain regions involved in assigning first-person-perspective comprise medial prefrontal, medial parietal and lateral temporoparietal cortex. These empirical findings complement recent neurobiologically oriented theories of self-consciousness which focus on the relation between the subject and his/her environment by supplying a neural basis for its key components.

Neuroimaging studies of language production and comprehension

The 1990s were dubbed the "Decade of the Brain." During this time there was a marked increase in the amount of neuroimaging work observing how the brain accomplishes many tasks, including the processing of language. In this chapter we review the past 15 years of neuroimaging research on language production and comprehension. The findings of these studies indicate that the processing involved in language use occurs in diffuse brain regions. These regions include Broca's and Wernicke's areas, primary auditory and visual cortex, and frontal regions in the left hemisphere, as well as in the right hemisphere homologues to these regions. We conclude the chapter by discussing the future of neuroimaging research into language production and comprehension.

A clinical and neurobehavioural review of high-functioning autism and Asperger's disorder

OBJECTIVE

To compare, contrast and review clinical and neuropsychological studies of high-functioning autism and Asperger's disorder.

METHOD

This paper reviews past and contemporary conceptualizations of autism and Asperger's disorder, together with epidemiological information, genetic and neurobehavioural findings. This paper focuses on neurobehavioural studies, in particular, executive functioning, lateralization, visual-perceptual and motor processing, which have provided an important source of information about the potential neurobiological dissociation that may exist between autism and Asperger's disorder.

RESULTS

The clinical profiles of autism and Asperger's disorder contain a mixture of psychiatric and neurological symptoms: for example, movement abnormalities (i.e. stereotyped behaviours, hand flapping, toe walking, whole-body movements), atypical processing of parts and wholes, verbal and non-verbal deficits, ritualistic/compulsive behaviour, disturbances in reciprocal social interaction and associated depression and anxiety. The considerable clinical overlap between autism and Asperger's disorder has led many to question whether Asperger's disorder is merely a mild form of autism, or whether it should be considered as a separate clinical entity.

CONCLUSION

In light of the growing body of epidemiological information, genetic, and neurobehavioural evidence that distinguishes autism from Asperger's disorder, it is premature to rule out the possibility that these disorders may be clinically, and possibly neurobiologically separate.

Neuroimaging of emotion and personality: scientific evidence and ethical considerations

Affective neuroscience has seen an explosion of research efforts using modern neuroimaging approaches to uncover the neural basis of emotion and personality. The first section of this paper reviews studies from the domains of affective and forensic neuroimaging. These studies illustrate some of the topics likely to be the subject of future ethical debates. The second section relates limitations of the neuroimaging approach to ethical considerations in predicting future psychopathology on the basis of brain state analysis.

Rethinking feelings: an FMRI study of the cognitive regulation of emotion

The ability to cognitively regulate emotional responses to aversive events is important for mental and physical health. Little is known, however, about neural bases of the cognitive control of emotion. The present study employed functional magnetic resonance imaging to examine the neural systems used to reappraise highly negative scenes in unemotional terms. Reappraisal of highly negative scenes reduced subjective experience of negative affect. Neural correlates of reappraisal were increased activation of the lateral and medial prefrontal regions and decreased activation of the amygdala and medial orbito-frontal cortex. These findings support the hypothesis that prefrontal cortex is involved in constructing reappraisal strategies that can modulate activity in multiple emotion-processing systems.

What does the frontomedian cortex contribute to language processing: coherence or theory of mind?

The frontomedian cortex (FMC) has been shown to be important for coherence processes in language comprehension, i.e., for establishing the pragmatic connection between successively presented sentences. The same brain region has a role during theory-of-mind processes, i.e., during the attribution of other people's actions to their motivations, beliefs, or emotions. In this study, we used event-related functional magnetic resonance imaging at 3 T to disentangle the relative contributions of the FMC to theory-of-mind (ToM) and coherence processes, respectively. The BOLD response of nine participants was recorded while they listened to pragmatically coherent or unrelated sentence pairs. Using a logic instruction for inanimate sentence pairs, ToM processing was discouraged during the first part of the experiment. Using explicit ToM instructions for sentence pairs mentioning human protagonists, ToM processing was induced during the second part. In three of the resulting four conditions a significant increase in the BOLD response was observed in FMC: when ToM instructions were given, both coherent and incoherent trials elicited frontomedian activation, in replication of previous results showing involvement of the FMC during ToM tasks. When logic instructions were given, the coherent trials, but not the incoherent trials, activated the FMC. These results clearly show that the FMC plays a role in coherence processes even in the absence of concomitant ToM processes. The findings support the view of this cortex having a domain-independent functionality related to volitional aspects of the initiation and maintenance of nonautomatic cognitive processes.

Lateralization in individuals with high-functioning autism and Asperger's disorder: a frontostriatal model

Neurobiological and behavioural studies of possible left hemisphere dysfunction in autism have generated conflicting results. Left hemisphere dysfunction may manifest in autism only in tasks that invoke executive functions. Moreover, left hemisphere dysfunction may underpin autism but not Asperger's disorder. We thus aimed to systematically investigate reports of anomalous lateralization in individuals with high-functioning autism and Asperger's disorder. Two of the tasks were sensitive to executive dysfunction: a serial choice reaction-time task and a Posner-type paradigm; the remaining tasks instead investigated aspects of perceptual lateralisation. Compared with age- and IQ-matched controls, the autism group displayed deficiencies in right hemispace (and by implication, left hemisphere) performance on both executive function tasks; however, this group demonstrated normal lateralization effects on the nonexecutive, visual-perceptual tasks. In contrast, the Asperger's disorder group showed similar laterality effects to their age- and IQ-matched controls on both executive and nonexecutive function tasks. The etiological relevance of this neurobehavioral dissociation between high-functioning autism and Asperger's disorder was discussed; in particular, it was suggested that the period where dominance shifts from right to left hemisphere is important in whatever process might dictate the emergence of either autism or Asperger's disorder.

Structural and functional magnetic resonance imaging of autism

Magnetic resonance imaging (MRI) of brain structures and function is uniquely suited to characterize the range of neuroanatomical and physiological changes that characterize the autism phenotype as it develops over time. In this review, we examine the scientific literature in MRI as applied to autism and related areas, over approximately the last decade, discussing findings which have emerged, methodological stumbling blocks which have been identified, and potential future directions. Structural MRI studies have recently begun to elucidate the neurodevelopmental underpinnings and brain-behavior relationships in autism while fMRI studies, building on the wealth of data in normal individuals, are beginning to characterize the underlying neuropsychological deficits of the disorder. Together, these two methods combine to contribute to a better understanding of the neural basis and brain phenotype of this disorder.

Neural systems involved in "theory of mind"

What is the nature of our ability to understand and reason about the beliefs of others--the possession of a "theory of mind", or ToM? Here, we review findings from imaging and lesion studies indicating that ToM reasoning is supported by a widely distributed neural system. Some functional components of this system, such as language-related regions of the left hemisphere, the frontal lobes and the right temporal parietal cortex, are not solely dedicated to the computation of mental states. However, the system also includes a core, domain-specific component that is centred on the amygdala circuitry. We provide a framework in which impairments of ToM can be viewed in terms of abnormalities of the core system, the failure of a co-opted system that is necessary for performance on a particular set of tasks, or the absence of an experiential trigger for the emergence of ToM.

Autism: a cognitive developmental riddle

It has been 60 years since the definitive descriptions of autism, yet it is only in the past decade that related advances in cognitive and basic neuroscience have begun to be incorporated in clinical practice. Some of the resultant clinical advances, which include a trend toward international standardization of diagnosis on the basis of behavioral criteria and which, in turn, seem to allow for earlier, more secure diagnosis and the application of behavioral therapy in early childhood, as well as more thorough genetic studies, are briefly reviewed. The three major defects in thought processing that are postulated by cognitive neuropsychologists to result in aberrant autistic behaviors are also reviewed and linked to recent functional imaging studies in autistic patients and some animal and bench research suggestive of both cortical and subcortical developmental vulnerabilities in autism. Overall it seems at least possible that neuroscientific research may yield results applicable to prevention or remediation of autism, a condition heretofore considered irremediable.

Studies of altered social cognition in neuropsychiatric disorders using functional neuroimaging

In this paper, we review studies using functional neuroimaging to examine cognition in neuropsychiatric disorders. The focus is on social cognition, which is a topic that has received increasing attention over the past few years. A network of brain regions is proposed for social cognition that includes regions involved in processes relevant to social functioning (for example, self reference and emotion). We discuss the alterations of activity in these areas in patients with autism, depression, schizophrenia, and posttraumatic stress disorders in relation to deficits in social behaviour and symptoms. The evidence to date suggests that there may be some specificity of the brain regions involved in these 4 disorders, but all are associated with dysfunction in the amygdala and dorsal cingulate gyrus. Although there is much work remaining in this area, we are beginning to understand the complex interactions of brain function and behaviour that lead to disruptions of social abilities.

Is autism due to cerebral-cerebellum disconnection?

Autism has been linked to thalidomide exposure at 20-24 days gestation. At this stage, the embryo is roughly the size of this 'C', and has yet to develop its brain (except for brainstem cranial motor nerve nuclei). The neuropathology responsible for autism is presently unknown, but whatever it is, it must logically be one that can be induced by such an early occurring brainstem cranial motor nerve nuclei defect. Many mental faculties impaired in autism (such as theory of mind) depend upon the prefrontal cortex. The maturation of cerebral-cerebellar connections, due to oddities in axon development, is vulnerable to pre-existing brainstem nuclei integrity. Many higher cognitions (including prefrontal ones) are dependent upon these links raising the possibility that abnormalities in them might produce autism. I conjecture that impaired cerebral-cerebellar connections, whether caused early, as by thalidomide, or later (including postnatally) by other factors, is the missing neuropathological cause of autism.

Mind blindness and the brain in autism

Experimental evidence shows that the inability to attribute mental states, such as desires and beliefs, to self and others (mentalizing) explains the social and communication impairments of individuals with autism. Brain imaging studies in normal volunteers highlight a circumscribed network that is active during mentalizing and links medial prefrontal regions with posterior superior temporal sulcus and temporal poles. The brain abnormality that results in mentalizing failure in autism may involve weak connections between components of this system.

Investigating the functional anatomy of empathy and forgiveness

Previous functional brain imaging studies suggest that the ability to infer the intentions and mental states of others (social cognition) is mediated by medial prefrontal cortex. Little is known about the anatomy of empathy and forgiveness. We used functional MRI to detect brain regions engaged by judging others' emotional states and the forgivability of their crimes. Ten volunteers read and made judgements based on social scenarios and a high level baseline task (social reasoning). Both empathic and forgivability judgements activated left superior frontal gyrus, orbitofrontal gyrus and precuneus. Empathic judgements also activated left anterior middle temporal and left inferior frontal gyri, while forgivability judgements activated posterior cingulate gyrus. Empathic and forgivability judgements activate specific regions of the human brain, which we propose contribute to social cohesion.

Bilateral medial prefrontal and temporal neocortical hypometabolism in children with epilepsy and aggression

PURPOSE

To identify brain regions with abnormal function in children with intractable partial epilepsy and aggressive behavior by using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography (PET).

METHODS

Six children (mean age, 9.9 years) with intractable partial epilepsy and aggressive behavior underwent detailed psychodevelopmental assessment and FDG-PET scanning. The objective technique of statistical parametric mapping (SPM) was applied to define focal abnormalities of glucose metabolism, and compared those with those of a group of normal adult subjects (n = 17) as well as age-matched children with epilepsy with similar seizure characteristics but without aggression (n = 7). The findings were analyzed further by using a region-of-interest (ROI) approach.

RESULTS

The aggressive children all showed developmental delay, and four of them also manifested autistic symptoms. SPM analysis demonstrated extensive glucose hypometabolism in the aggressive group bilaterally in the temporal and prefrontal cortex compared with that in normal adult controls. A focal area of medial prefrontal glucose hypometabolism was defined in the aggressive children as compared with the nonaggressive pediatric group with SPM, whereas ROI comparison of these groups confirmed prefrontal hypometabolism and also showed glucose hypometabolism of the temporal neocortex in the aggressive children. Severity of aggression correlated inversely with glucose metabolism of the left temporal as well as bilateral medial prefrontal cortex.

CONCLUSIONS

Bilateral prefrontal and temporal neocortical brain glucose hypometabolism in children with epilepsy and aggressive behavior may indicate a widespread dysfunction of cortical regions, which normally exert an inhibitory effect on subcortical aggressive impulses. PET studies may be used to elucidate the neurobiologic basis of aggressive behavior in children.

Neuropsychologie des Autismus

Zusammenfassung: Autismus ist eine persistierende, durch soziale und kommunikative Defizite sowie stereotypes, repetitives Verhalten charakterisierte tiefgreifende Entwicklungsstörung mit Beginn vor Vollendung des 3. Lebensjahres. Vielfältige organische Befunde weisen auf eine neurobiologische Basis des Syndroms hin. Wenngleich die molekulargenetischen Mechanismen noch unklar sind, legen Zwillings- und Familienstudien ätiologisch eine Involvierung hereditärer Faktoren nahe. Auf neuropsychologischer Ebene haben im Autismus in der jüngeren Vergangenheit vor allem drei kognitive Theorien zum besseren Verständnis der zugrunde liegenden gestörten Denkprozesse und zur Integration unterschiedlicher Erklärungsansätze beigetragen: die theory of mind, Exekutivfunktionen und die Theorie der (schwachen) zentralen Kohärenz. Für die zukünftige neuropsychologische Erforschung des Autismus sind die Konkretisierung und verbesserte Operationalisierung dieser kognitiven Theorien, die Einführung methodischer Standards sowie die Entscheidung über eine kategoriale versus dimensionale Betrachtung des Autismus von Bedeutung.

Mind reading: neural mechanisms of theory of mind and self-perspective

Human self-consciousness as the metarepresentation of ones own mental states and the so-called theory of mind (TOM) capacity, which requires the ability to model the mental states of others, are closely related higher cognitive functions. We address here the issue of whether taking the self-perspective (SELF) or modeling the mind of someone else (TOM) employ the same or differential neural mechanisms. A TOM paradigm was used and extended to include stimulus material that involved TOM and SELF capacities in a two-way factorial design. A behavioral study in 42 healthy volunteers showed that TOM and SELF induced differential states of mind: subjects assigned correctly first or third person pronouns when providing responses to the stimuli. Following the behavioral study, we used functional magnetic resonance imaging (fMRI) in eight healthy, right-handed males to study the common and differential neural mechanisms underlying TOM and SELF. The main factor TOM led to increased neural activity in the anterior cingulate cortex and left temporopolar cortex. The main factor SELF led to increased neural activity in the right temporoparietal junction and in the anterior cingulate cortex. A significant interaction of both factors TOM and SELF was observed in the right prefrontal cortex. These divergent neural activations in response to TOM and SELF suggest that these important differential mental capacities of human self-consciousness are implemented at least in part in distinct brain regions. Press

Current directions in research on autism

One of the most active areas of current research in the field of developmental disorders is autism. Since the NIH State of the Science conference, held in 1995 (Bristol et al. [1996] J. Autism Dev. Disorders 26:121-154), funding opportunities for comprehensive research programs addressing genetic, neurobiological, and behavioral aspects of this complex disorder have grown exponentially. Although we are far from having a complete understanding of the causes and deficits that define autism, significant progress has been made over the past few years. In this review, we summarize recent developments across a number of different areas of research in the field of autism, including diagnosis; defining the phenotypic features in individuals with autism; genetic bases; and neurobiological deficits.

Atypical patterns of cerebral motor activation in autism: a functional magnetic resonance study

BACKGROUND

Early neurodevelopmental pathogenesis in autism potentially affects emerging functional maps, but little imaging evidence is available.

METHODS

We studied eight male autistic and eight matched normal subjects, using functional magnetic resonance imaging during visually paced finger movement, compared to a control condition (visual stimulation in the absence of motor response).

RESULTS

Groupwise analyses showed activation in contralateral perirolandic cortex, basal ganglia, and thalamus, bilateral supplementary motor area, and ipsilateral cerebellum for both groups. However, activations were less pronounced in the autism group. Direct group comparisons demonstrated greater activation in perirolandic and supplementary motor areas in the control group and greater activation (or reduced deactivation) in posterior and prefrontal cortices in the autism group. Intraindividual analyses further showed that strongest activations were consistently located along the contralateral central sulcus in control subjects but occurred in locations differing from individual to individual in the autism group.

CONCLUSIONS

Our findings, though based on a rather small sample, suggest abnormal individual variability of functional maps and less distinct regional activation/deactivation patterns in autism. The observations may relate to known motor impairments in autism and are compatible with the general hypothesis of disturbances of functional differentiation in the autistic cerebrum.

The neurobiology of social cognition

Recent studies have begun to elucidate the roles played in social cognition by specific neural structures, genes, and neurotransmitter systems. Cortical regions in the temporal lobe participate in perceiving socially relevant stimuli, whereas the amygdala, right somatosensory cortices, orbitofrontal cortices, and cingulate cortices all participate in linking perception of such stimuli to motivation, emotion, and cognition. Open questions remain about the domain-specificity of social cognition, about its overlap with emotion and with communication, and about the methods best suited for its investigation.

Movement preparation in high-functioning autism and Asperger disorder: a serial choice reaction time task involving motor reprogramming

Autism and Asperger disorder have long been associated with movement abnormalities, although the neurobehavioural details of these abnormalities remain poorly defined. Clumsiness has traditionally been associated with Asperger disorder but not autism, although this is controversial. Others have suggested that both groups demonstrate a similar global motor delay. In this study we aimed to determine whether movement preparation or movement execution was atypical in these disorders and to describe any differences between autism and Asperger disorder. A simple motor reprogramming task was employed. The results indicated that individuals with autism and Asperger disorder have atypical movement preparation with an intact ability to execute movement. An atypical deficit in motor preparation was found in Asperger disorder, whereas movement preparation was characterized by a "lack of anticipation" in autism. The differences in movement preparation profiles in these disorders were suggested to reflect differential involvement of the fronto-striatal region, in particular the supplementary motor area and anterior cingulate.

Das Asperger Syndrom. Eine aktuelle Übersicht

Zusammenfassung Das Asperger-Syndrom (AS) ist gekennzeichnet durch eine ausgeprägte Kontakt- und Kommunikationsstörung, die meist im Vorschulalter evident wird, sowie durch eine qualitative Beeinträchtigung des Interaktionsverhaltens, mangelndes Einfühlungsvermögen, motorische Auffälligkeiten und (inkonstant) ausgeprägte Sonderinteressen. Es wird zu den tiefgreifenden Entwicklungsstörungen gerechnet. Als Ursache werden genetische Faktoren angenommen im Verein mit umschriebenen Hirnfunktionsstörungen und neuropsychologischen Ausfällen, die alle auf eine Einschränkung nonverbalen Lernens hinweisen, wobei sich das Intelligenzniveau meist im Normbereich bewegt. Die Behandlung stützt sich auf verhaltenstherapeutische Vorgehensweisen zur Einübung sozialer Fertigkeiten sowie die angemessene schulische Förderung und Beschäftigung, unter Berücksichtigung der individuellen Besonderheiten des Einzelfalles. Eine medikamentöse Behandlung kann angezeigt sein, wenn besondere Symptome wie Hyperaktivität und Unruhe, aggressives Verhalten, Schlafstörungen oder depressive Verstimmungen auftreten.

Dissociation between 'theory of mind' and executive functions in a patient with early left amygdala damage

There have been recent suggestions that the amygdala may be involved in the development or mediation of 'theory of mind'. We report a patient, B.M., with early or congenital left amygdala damage who, by adulthood, had received the psychiatric diagnoses of schizophrenia and Asperger's syndrome. We conducted a series of experimental investigations to determine B.M.'s cognitive functioning. In line with his diagnoses, B.M. was found to be severely impaired in his ability to represent mental states. Following this, we conducted a second series of studies to determine B.M.'s executive functioning. In the literature, there have been frequent claims that theory of mind is mediated by general executive functioning. B.M. showed no indication of executive function impairment, passing 16 tests assessing his ability to inhibit dominant responses, create and maintain goal-related behaviours, and temporally sequence behaviour. The findings are discussed with reference to models regarding the role of the amygdala in the development of theory of mind and the degree of dissociation between theory of mind and executive functioning. We conclude that theory of mind is not simply a function of more general executive functions, and that executive functions can develop and function on-line, independently of theory of mind. Moreover, we conclude that the amygdala may play some role in the development of the circuitry mediating theory of mind.

The functional neuroanatomy of social behaviour: changes in cerebral blood flow when people with autistic disorder process facial expressions

Although high-functioning individuals with autistic disorder (i.e. autism and Asperger syndrome) are of normal intelligence, they have life-long abnormalities in social communication and emotional behaviour. However, the biological basis of social difficulties in autism is poorly understood. Facial expressions help shape behaviour, and we investigated if high-functioning people with autistic disorder show neurobiological differences from controls when processing emotional facial expressions. We used functional MRI to investigate brain activity in nine adults with autistic disorder (mean age +/- standard deviation 37 +/- 7 years; IQ 102 +/- 15) and nine controls (27 +/- 7 years; IQ 116 +/- 10) when explicitly (consciously) and implicitly (unconsciously) processing emotional facial expressions. Subjects with autistic disorder differed significantly from controls in the activity of cerebellar, mesolimbic and temporal lobe cortical regions of the brain when processing facial expressions. Notably, they did not activate a cortical 'face area' when explicitly appraising expressions, or the left amygdala region and left cerebellum when implicitly processing emotional facial expressions. High-functioning people with autistic disorder have biological differences from controls when consciously and unconsciously processing facial emotions, and these differences are most likely to be neurodevelopmental in origin. This may account for some of the abnormalities in social behaviour associated with autism.

Functional neuroimaging of autistic disorders

Functional neuroimaging methods hold promise for elucidating the neurobiology of autistic disorders, yet they present difficult practical and scientific challenges when applied to these complex and heterogeneous syndromes. Single-state studies of brain metabolism and blood flow thus far have failed to yield consistent findings, but suggest considerable variability in regional patterns of cerebral synaptic activity. Patients with idiopathic autism are less likely to show abnormalities than are patients with comorbid illness or epilepsy. Activation studies have begun to suggest alterations in brain organization for language and cognition. Neurotransmitter studies using positron emission tomography (PET) suggest abnormalities of serotonergic and dopaminergic function. Studies using magnetic resonance spectroscopy (MRS) have begun to document metabolic deficits in the frontal cortex and cerebellum. A single study using magnetoencephalography suggests a high incidence of epileptiform activity in children with autistic regression. Research needs include well-controlled developmental studies, particularly of young subjects and relatively homogeneous subgroups, which balance scientific rigor with ethical constraints. Investigations of the serotonergic and dopaminergic systems, limbic-based memory and emotional systems, and the role of epileptiform activity in autism represent priorities for future research.

Developmental depersonalization: the prefrontal cortex and self-functions in autism

The human self model suggests that the construct of self involves functions such as agency, body-centered spatial perspectivity, and long-term unity. Vogeley, Kurthen, Falkai, and Maieret (1999) suggest that agency is subserved by the prefrontal cortex and other association areas of the cortex, spatial perspectivity by the prefrontal cortex and the parietal lobes, and long-term unity by the prefrontal cortex and the temporal lobes and that all of these functions are impaired in schizophrenia. Exploring the connections between the prefrontal cortex and the construct of self, the present article extends the application of the self model to autism. It suggests that in contrast to schizophrenia, agency and spatial perspectivity are probably preserved in autism, but that, similarly to schizophrenia, long-term unity is probably impaired. This hypothesis is compatible with a model of neuropsychological dysfunction in autism in a neural network including parts of the prefrontal cortex, the temporal lobes, and the cerebellum.

Movement and mind: a functional imaging study of perception and interpretation of complex intentional movement patterns

We report a functional neuroimaging study with positron emission tomography (PET) in which six healthy adult volunteers were scanned while watching silent computer-presented animations. The characters in the animations were simple geometrical shapes whose movement patterns selectively evoked mental state attribution or simple action description. Results showed increased activation in association with mental state attribution in four main regions: medial prefrontal cortex, temporoparietal junction (superior temporal sulcus), basal temporal regions (fusiform gyrus and temporal poles adjacent to the amygdala), and extrastriate cortex (occipital gyrus). Previous imaging studies have implicated these regions in self-monitoring, in the perception of biological motion, and in the attribution of mental states using verbal stimuli or visual depictions of the human form. We suggest that these regions form a network for processing information about intentions, and speculate that the ability to make inferences about other people's mental states evolved from the ability to make inferences about other creatures' actions.

A componential view of theory of mind: evidence from Williams syndrome

In this paper we argue that there are two distinct components of a theory of mind: a social-cognitive and a social-perceptual component. Evidence for this proposal is presented from various sources, including studies of children with Williams syndrome, a rare genetic neurodevelopmental disorder. Earlier work has demonstrated that people with Williams syndrome appear to be spared in the social-perceptual component of a theory of mind. In this paper we present evidence that they are not spared in the social-cognitive component of theory of mind. Three experiments with young children with Williams syndrome were conducted. In each experiment the children with Williams syndrome were compared to age-, IQ-, and language-matched children with Prader-Willi syndrome, and children with non-specific mental retardation. The experiments used different measures of theory of mind ability, including false belief (Experiment 1), explanation of action (Experiment 2), and recognition of emotional expressions (Experiment 3). In none of these experiments did the children with Williams syndrome evidence superior performance compared to the control groups. The results from this and other studies on Williams syndrome support the view that the social-cognitive and social-perceptual components of a theory of mind are dissociable. In Williams syndrome only the latter components, which are linked to distinct neurobiological substrates, are spared.

Neuroimaging in child and adolescent psychiatric disorders

Neuroimaging in child psychiatry is a rapidly developing field and the number of different techniques being used is increasing rapidly. This review describes the current status of neuroimaging in childhood psychopathology and discusses limitations of the various studies. As yet, no specific and consistent abnormality has been detected in childhood psychiatric disorders. Obsessive compulsive disorder has shown the most consistent findings so far, with orbitofrontal cortex and the caudate nucleus being implicated. Better understanding of the corticostriatal neural networks will shed more light on the neurodevelopmental disorders of childhood.

Functional neuroimaging in child psychiatry

Functional neuroimaging in child psychiatry presents unique scientific, ethical, and technical challenges. The study of childhood disorders presupposes knowledge of neurodevelopment and brain maturation. However, much of human brain science is based on inferences from animal work and indirect neurochemical measures from body fluids. Neuroimaging can examine brain development directly in humans. The benefits can be enormous for learning how and when to intervene to prevent or treat a disorder. These unprecedented potential gains are countered by complex and difficult ethical issues. Technical advances can reduce ethical concerns by minimizing risks. They also promise to enhance the sensitivity and specificity of the measures (eg, by improving spatial and temporal resolution). Judiciously designed investigations will permit the testing of a priori hypotheses built on rational models of neuropathology. Finally, it is the integration of scientific knowledge across the various fields of neuroscience and clinical research that will push the limits of our understanding of health and disease.

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.

Reading the mind in cartoons and stories: an fMRI study of 'theory of mind' in verbal and nonverbal tasks

Previous functional imaging studies have explored the brain regions activated by tasks requiring 'theory of mind'--the attribution of mental states. Tasks used have been primarily verbal, and it has been unclear to what extent different results have reflected different tasks, scanning techniques, or genuinely distinct regions of activation. Here we report results from a functional magnetic resonance imaging study (fMRI) involving two rather different tasks both designed to tap theory of mind. Brain activation during the theory of mind condition of a story task and a cartoon task showed considerable overlap, specifically in the medial prefrontal cortex (paracingulate cortex). These results are discussed in relation to the cognitive mechanisms underpinning our everyday ability to 'mind-read'.

Development of theory of mind and executive control

Several recent studies have demonstrated a developmental link, in the age range of 3-5 years, between the acquisition of a 'theory of mind' and self control. In this review, we consider the existence of such a link in assessing five competing theoretical hypotheses that might help us to understand the nature of this developmental advance: (1) executive control depends on theory of mind; (2) theory of mind development depends on executive control; (3) the relevant theory of mind tasks require executive control; (4) both kinds of task require the same kind of embedded conditional reasoning; (5) theory of mind and executive control involve the same brain region. We briefly describe these theoretical accounts and evaluate them in the light of existing empirical evidence. At present, only account (3) can be ruled out with some confidence.

Exploring the process of inference generation in sarcasm: a review of normal and clinical studies

This article evaluates two theoretical accounts of how sarcasm is understood; the traditional model, which asserts that listeners derive a counterfactual inference from the sarcastic comment, and relevance theory, which asserts that listeners recognize sarcasm as a scornful echo of a previous assertion. Evidence from normal speakers provides only partial support for both theories. Evidence from brain-injured populations suggests that aspects of the pragmatic process can be arrested in ways not predicted by either theory. It is concluded that sarcasm is more effortful to process than nonsarcastic comments and that inferences about the facts of the situation and the mental state of the speaker (e.g., attitudes, knowledge, and intentions) are important to comprehending sarcasm. It is questioned whether inferences about mental state are relatively more difficult for brain-injured subjects and, if so, whether this is a continuum of difficulty or reflects reliance upon different cognitive processes.