Is integer arithmetic fundamental to mental processing?: the mind's secret arithmetic

Should absolute pitch be considered as a unique kind of absolute sensory judgment in humans? A systematic and theoretical review of the literature

Absolute pitch is the name given to the rare ability to identify a musical note in an automatic and effortless manner without the need for a reference tone. Those individuals with absolute pitch can, for example, name the note they hear, identify all of the tones of a given chord, and/or name the pitches of everyday sounds, such as car horns or sirens. Hence, absolute pitch can be seen as providing a rare example of absolute sensory judgment in audition. Surprisingly, however, the intriguing question of whether such an ability presents unique features in the domain of sensory perception, or whether instead similar perceptual skills also exist in other sensory domains, has not been explicitly addressed previously. In this paper, this question is addressed by systematically reviewing research on absolute pitch using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) method. Thereafter, we compare absolute pitch with two rare types of sensory experience, namely synaesthesia and eidetic memory, to understand if and how these phenomena exhibit similar features to absolute pitch. Furthermore, a common absolute perceptual ability that has been often compared to absolute pitch, namely colour perception, is also discussed. Arguments are provided supporting the notion that none of the examined abilities can be considered like absolute pitch. Therefore, we conclude by suggesting that absolute pitch does indeed appear to constitute a unique kind of absolute sensory judgment in humans, and we discuss some open issues and novel directions for future research in absolute pitch.

Neuroenhancement of High-Level Cognition: Evidence for Homeostatic Constraints of Non-invasive Brain Stimulation

Neuroenhancement aims to improve cognitive performance in typically and atypically functioning populations. However, it is currently debated whether it is also effective in exceptionally high-functioning individuals. Present theories suggest that homeostatic set points for learning and cortical plasticity limit the beneficial effects of neuroenhancement. To examine this possibility, we used transcranial random noise stimulation (tRNS) to non-invasively stimulate bilateral dorsolateral prefrontal cortices (DLPFC) of the world champion in mental calculation, G.M. TRNS did not change G.M.’s calculation performance compared to sham stimulation on an exceptionally complex arithmetic task. However, a sample of mathematicians who were not calculation prodigies (N = 6) showed reduced accuracy on a complex multiplication task in response to tRNS, relative to sham. Our findings suggest that there may be an upper limit for cognitive enhancement and that further attempts to enhance performance using tRNS (at least with the current parameters) may impair optimal functioning. The discussion of potential negative effects of brain stimulation for cognitive enhancement is critical, as it may lead to unintended impairments in different subgroups of the population.

Trust the Process: A New Scientific Outlook on Psychodramatic Spontaneity Training

Human mind is hypothesis-driven and our observations of the world are strongly shaped by preconceptions. This "top-down" principle is biologically driven and contraindicative to spontaneity, which is non-linear, condensed, and initially incomprehensible. My first argument is that spontaneity entails "bottom up" information processing, as articulated in the hierarchical neurocognitive model of perception. My second argument is that changing the balance between these two processes is important and feasible. Insights from psychodynamic transference and savant syndrome are presented to support these ideas. Uniting these contemporary notions with some essentials of J. L. Moreno's philosophy is my third goal. By violating predictions and expectations, psychodrama interferes with top-down "conserved" processing and cultivates here and now, stimulus-dependent spontaneous acts. Further evidence is presented in support of the claim that adult spontaneity leads to enhanced cognition and creativity through imitating the child's brain, as Moreno envisioned. Because spontaneity is formed before having the evidence for its truth or adequacy, it entails, in adults, overcoming apprehensions about acting without a theory in mind. This is what trusting-the-process means and it requires training, which psychodrama fosters on its stage laboratory.

The evolution of cognitive mechanisms in response to cultural innovations

When humans and other animals make cultural innovations, they also change their environment, thereby imposing new selective pressures that can modify their biological traits. For example, there is evidence that dairy farming by humans favored alleles for adult lactose tolerance. Similarly, the invention of cooking possibly affected the evolution of jaw and tooth morphology. However, when it comes to cognitive traits and learning mechanisms, it is much more difficult to determine whether and how their evolution was affected by culture or by their use in cultural transmission. Here we argue that, excluding very recent cultural innovations, the assumption that culture shaped the evolution of cognition is both more parsimonious and more productive than assuming the opposite. In considering how culture shapes cognition, we suggest that a process-level model of cognitive evolution is necessary and offer such a model. The model employs relatively simple coevolving mechanisms of learning and data acquisition that jointly construct a complex network of a type previously shown to be capable of supporting a range of cognitive abilities. The evolution of cognition, and thus the effect of culture on cognitive evolution, is captured through small modifications of these coevolving learning and data-acquisition mechanisms, whose coordinated action is critical for building an effective network. We use the model to show how these mechanisms are likely to evolve in response to cultural phenomena, such as language and tool-making, which are associated with major changes in data patterns and with new computational and statistical challenges.

Savant-like Numerosity Skills Revealed in Normal People by Magnetic Pulses

Oliver Sacks observed autistic twins who instantly guessed the exact number of match-sticks that had just fallen on the floor, saying in unison “111”. To test the suggestion that normal individuals have the capacity for savant numerosity, we temporarily simulated the savant condition in normal people by inhibiting the left anterior temporal lobe of twelve participants with repetitive transcranial magnetic stimulation (rTMS). This site has been implicated in the savant condition. Ten participants improved their ability to accurately guess the number of discrete items immediately following rTMS and, of these, eight became worse at guessing as the effects of the pulses receded. The probability of as many as eight out of twelve people doing best just after rTMS and not after sham stimulation by chance alone is less than one in one thousand.

Cognitive Expertise: An ALE Meta-Analysis

Expert performance constitutes the endpoint of skill acquisition and is accompanied by widespread neuroplastic changes. To reveal common mechanisms of reorganization associated with long-term expertise in a cognitive domain (mental calculation, chess, language, memory, music without motor involvement), we used activation likelihood estimation meta-analysis and compared brain activation of experts to nonexperts. Twenty-six studies matched inclusion criteria, most of which reported an increase and not a decrease of activation foci in experts. Increased activation occurred in the left rolandic operculum (OP 4) and left primary auditory cortex and in bilateral premotor cortex in studies that used auditory stimulation. In studies with visual stimulation, experts showed enhanced activation in the right inferior parietal cortex (area PGp) and the right lingual gyrus. Experts' brain activation patterns seem to be characterized by enhanced or additional activity in domain-specific primary, association, and motor structures, confirming that learning is localized and very specialized.

Treating autism by targeting the temporal lobes

Compelling new findings suggest that an early core signature of autism is a deficient left anterior temporal lobe response to language and an atypical over-activation of the right anterior temporal lobe. Intriguingly, our recent results from an entirely different line of reasoning and experiments also show that applying cathodal stimulation (suppressing) at the left anterior temporal lobe together with anodal stimulation (facilitating) at the right anterior temporal lobe, by transcranial direct current stimulation (tDCS), can induce some autistic-like cognitive abilities in otherwise normal adults. If we could briefly induce autistic like cognitive abilities in healthy individuals, it follows that we might be able to mitigate some autistic traits by reversing the above stimulation protocol, in an attempt to restore the typical dominance of the left anterior temporal lobe. Accordingly, we hypothesize that at least some autistic traits can be mitigated, by applying anodal stimulation (facilitating) at the left anterior temporal lobe together with cathodal stimulation (suppressing) at the right anterior temporal lobe. Our hypothesis is supported by strong convergent evidence that autistic symptoms can emerge and later reverse due to the onset and subsequent recovery of various temporal lobe (predominantly the left) pathologies. It is also consistent with evidence that the temporal lobes (especially the left) are a conceptual hub, critical for extracting meaning from lower level sensory information to form a coherent representation, and that a deficit in the temporal lobes underlies autistic traits.

Atypical resource allocation may contribute to many aspects of autism

Based on a review of the literature and on reports by people with autism, this paper suggests that atypical resource allocation is a factor that contributes to many aspects of autism spectrum conditions, including difficulties with language and social cognition, atypical sensory and attentional experiences, executive and motor challenges, and perceptual and conceptual strengths and weaknesses. Drawing upon resource theoretical approaches that suggest that perception, cognition, and action draw upon multiple pools of resources, the approach hypothesizes that compared with resources in typical cognition, resources in autism are narrowed or reduced, especially in people with strong sensory symptoms. In narrowed attention, resources are restricted to smaller areas and to fewer modalities, stages of processing, and cognitive processes than in typical cognition; narrowed resources may be more intense than in typical cognition. In reduced attentional capacity, overall resources are reduced; resources may be restricted to fewer modalities, stages of processing, and cognitive processes than in typical cognition, or the amount of resources allocated to each area or process may be reduced. Possible neural bases of the hypothesized atypical resource allocation, relations to other approaches, limitations, and tests of the hypotheses are discussed.

Seeing mathematics: perceptual experience and brain activity in acquired synesthesia

We studied the patient JP who has exceptional abilities to draw complex geometrical images by hand and a form of acquired synesthesia for mathematical formulas and objects, which he perceives as geometrical figures. JP sees all smooth curvatures as discrete lines, similarly regardless of scale. We carried out two preliminary investigations to establish the perceptual nature of synesthetic experience and to investigate the neural basis of this phenomenon. In a functional magnetic resonance imaging (fMRI) study, image-inducing formulas produced larger fMRI responses than non-image inducing formulas in the left temporal, parietal and frontal lobes. Thus our main finding is that the activation associated with his experience of complex geometrical images emerging from mathematical formulas is restricted to the left hemisphere.

The neural architecture of expert calendar calculation: a matter of strategy?

Savants and prodigies are individuals with exceptional skills in particular mental domains. In the present study we used functional magnetic resonance imaging to examine neural correlates of calendar calculation in two individuals, a savant with Asperger's disorder and a self-taught mathematical prodigy. If there is a modular neural organization of exceptional performance in a specific mental domain, calendar calculation should be reflected in a considerable overlap in the recruitment of brain circuits across expert individuals. However, considerable individual differences in activation patterns during calendar calculation were noted. The present results indicate that activation patterns produced by complex mental processing, such as calendar calculation, seem to be influenced strongly by learning history and idiosyncratic strategy usage rather than a modular neural organization. Thus, well-known individual differences in complex cognition play a major role even in experts with exceptional abilities in a particular mental domain and should in particular be considered when examining the neural architecture of complex mental processes and skills.

Electromagnetic evidence of altered visual processing in autism

Individuals with autism spectrum disorder (ASD) demonstrate intact or superior local processing of visual-spatial tasks. We investigated the hypothesis that in a disembedding task, autistic individuals exhibit a more local processing style than controls, which is reflected by altered electromagnetic brain activity in response to embedded stimuli and enhanced activity of early visual areas. Ten autistic and ten matched control participants underwent 151-channel whole-head magnetoencephalography. Participants were presented with 400 embedded or isolated letters ('S' or 'H') and asked to indicate which of the two letters was shown. Performance was equal in both groups, but event-related magnetic fields differed between groups in an early (100-150 ms) and a later (350-400 ms) time window. In the early time window, autistic individuals differed from control participants in the embedded, but not in the isolated condition, reflecting reduced processing of the irrelevant context in autistic individuals. In the later time window, amplitude differences between the embedded and isolated conditions were measured in control participants only, suggesting that "disembedding" processes were not required in autistic individuals. Source localisation indicated that activity in individuals with ASD peaked in the primary visual cortex in both conditions and time windows indicating an effortless (automatic, bottom-up) local process, whereas activity in controls peaked outside the visual cortex.

Facilitate insight by non-invasive brain stimulation

Our experiences can blind us. Once we have learned to solve problems by one method, we often have difficulties in generating solutions involving a different kind of insight. Yet there is evidence that people with brain lesions are sometimes more resistant to this so-called mental set effect. This inspired us to investigate whether the mental set effect can be reduced by non-invasive brain stimulation. 60 healthy right-handed participants were asked to take an insight problem solving task while receiving transcranial direct current stimulation (tDCS) to the anterior temporal lobes (ATL). Only 20% of participants solved an insight problem with sham stimulation (control), whereas 3 times as many participants did so (p = 0.011) with cathodal stimulation (decreased excitability) of the left ATL together with anodal stimulation (increased excitability) of the right ATL. We found hemispheric differences in that a stimulation montage involving the opposite polarities did not facilitate performance. Our findings are consistent with the theory that inhibition to the left ATL can lead to a cognitive style that is less influenced by mental templates and that the right ATL may be associated with insight or novel meaning. Further studies including neurophysiological imaging are needed to elucidate the specific mechanisms leading to the enhancement.

The mind of the mnemonists: an MEG and neuropsychological study of autistic memory savants

About 10% of autistic individuals exhibit some form of islets of abilities in the face of serious intellectual or mental disability ("savant syndrome"). The aim of this study was to investigate brain mechanisms in a sample of autistic subjects with outstanding memory. We investigated seven mnemonist savants with high-functioning autism spectrum disorder and seven matched controls with 151-channel whole-head magnetencephalography in a continuous old-new paradigm. They were presented with 300 pseudowords and 300 shapes and had to indicate by button press, whether the presented stimulus had been shown before. Unexpectedly, mnemonist savants did not perform better than controls, but were outperformed in the recognition of pseudowords. Accordingly, event-related magnetic fields elicited by pseudowords showed widespread old-new effects in controls, but not in savants. A source analysis of its early components revealed right occipital activation in savants, but left parietal activation in controls. This might be related to a visual processing style in mnemonist savants that proved to be inefficient in this task. During the possibly familiarity-based recognition of shapes, there were earlier and more widespread bilateral old-new effects in mnemonist savants, what might reflect their experience with figural material. In a neuropsychological test battery, mnemonist savants performed comparably to autistic people without special memory skills. However, a different factor structure of these tests pointed to a different organization of memory in mnemonist savants compared to controls that is characterized by its relative independence of general intelligence.

When seeing depends on knowing: adults with Autism Spectrum Conditions show diminished top-down processes in the visual perception of degraded faces but not degraded objects

Behavioural, neuroimaging and neurophysiological approaches emphasise the active and constructive nature of visual perception, determined not solely by the environmental input, but modulated top-down by prior knowledge. For example, degraded images, which at first appear as meaningless 'blobs', can easily be recognized as, say, a face, after having seen the same image un-degraded. This conscious perception of the fragmented stimuli relies on top-down priming influences from systems involved in attention and mental imagery on the processing of stimulus attributes, and feature-binding [Dolan, R. J., Fink, G. R., Rolls, E., Booth, M., Holmes, A., Frackowiak, R. S. J., et al. (1997). How the brain learns to see objects and faces in an impoverished context. Nature, 389, 596-599]. In Autism Spectrum Conditions (ASC), face processing abnormalities are well-established, but top-down anomalies in various domains have also been shown. Thus, we tested two alternative hypotheses: (i) that people with ASC show overall reduced top-down modulation in visual perception, or (ii) that top-down anomalies affect specifically the perception of faces. Participants were presented with sets of three consecutive images: degraded images (of faces or objects), corresponding or non-corresponding grey-scale photographs, and the same degraded images again. In a passive viewing sequence we compared gaze times (an index of focal attention) on faces/objects vs. background before and after viewers had seen the undegraded photographs. In an active viewing sequence, we compared how many faces/objects were identified pre- and post-exposure. Behavioural and gaze tracking data showed significantly reduced effects of prior knowledge on the conscious perception of degraded faces, but not objects in the ASC group. Implications for future work on the underlying mechanisms, at the cognitive and neurofunctional levels, are discussed.

Do calendrical savants use calculation to answer date questions? A functional magnetic resonance imaging study

Calendrical savants can name the weekdays for dates from different years with remarkable speed and accuracy. Whether calculation rather than just memory is involved is disputed. Grounds for doubting whether they can calculate are reviewed and criteria for attributing date calculation skills to them are discussed. At least some calendrical savants possess date calculation skills. A behavioural characteristic observed in many calendrical savants is increased response time for questions about more remote years. This may be because more remote years require more calculation or because closer years are more practised. An experiment is reported that used functional magnetic resonance imaging to attempt to discriminate between these explanations. Only two savants could be scanned and excessive head movement corrupted one savant's mental arithmetic data. Nevertheless, there was increased parietal activation during both mental arithmetic and date questions and this region showed increased activity with more remote dates. These results suggest that the calendrical skills observed in savants result from intensive practice with calculations used in solving mental arithmetic problems. The mystery is not how they solve these problems, but why.

Explaining and inducing savant skills: privileged access to lower level, less-processed information

I argue that savant skills are latent in us all. My hypothesis is that savants have privileged access to lower level, less-processed information, before it is packaged into holistic concepts and meaningful labels. Owing to a failure in top-down inhibition, they can tap into information that exists in all of our brains, but is normally beyond conscious awareness. This suggests why savant skills might arise spontaneously in otherwise normal people, and why such skills might be artificially induced by low-frequency repetitive transcranial magnetic stimulation. It also suggests why autistic savants are atypically literal with a tendency to concentrate more on the parts than on the whole and why this offers advantages for particular classes of problem solving, such as those that necessitate breaking cognitive mindsets. A strategy of building from the parts to the whole could form the basis for the so-called autistic genius. Unlike the healthy mind, which has inbuilt expectations of the world (internal order), the autistic mind must simplify the world by adopting strict routines (external order).

Enhanced perception in savant syndrome: patterns, structure and creativity

According to the enhanced perceptual functioning (EPF) model, autistic perception is characterized by: enhanced low-level operations; locally oriented processing as a default setting; greater activation of perceptual areas during a range of visuospatial, language, working memory or reasoning tasks; autonomy towards higher processes; and superior involvement in intelligence. EPF has been useful in accounting for autistic relative peaks of ability in the visual and auditory modalities. However, the role played by atypical perceptual mechanisms in the emergence and character of savant abilities remains underdeveloped. We now propose that enhanced detection of patterns, including similarity within and among patterns, is one of the mechanisms responsible for operations on human codes, a type of material with which savants show particular facility. This mechanism would favour an orientation towards material possessing the highest level of internal structure, through the implicit detection of within- and between-code isomorphisms. A second mechanism, related to but exceeding the existing concept of redintegration, involves completion, or filling-in, of missing information in memorized or perceived units or structures. In the context of autistics' enhanced perception, the nature and extent of these two mechanisms, and their possible contribution to the creativity evident in savant performance, are explored.

Reducing false memories by magnetic pulse stimulation

False memories are ubiquitous and often to our detriment. Yet, certain pathologies, including anterior temporal lobe dementia and autism, can lead to literal recall and thus greater resistance to false memories. This inspired us to reduce false memories by temporarily inhibiting the left anterior temporal lobe, using low frequency magnetic pulse stimulation. This site has been implicated in semantic memory and conceptual labelling. After active stimulation, participants in the sham/TMS group had 36% fewer false memories than they had with sham stimulation, and intact veridical memory. This is comparable to the improvement that people with autism and semantic dementia show over "normal" individuals. This finding suggests a potential method for reducing certain types of false memories.

Deactivation of the limbic system during acute psychosocial stress: evidence from positron emission tomography and functional magnetic resonance imaging studies

BACKGROUND

Stress-induced metabolic changes can have detrimental health effects. Newly developed paradigms to investigate stress in neuroimaging environments allow the assessment of brain activation changes in association with the perception of and the metabolic response to stress.

METHODS

We exposed human subjects to a psychosocial stressor in one positron emission tomography (n = 10) and one functional magnetic resonance imaging (fMRI; n = 40) experiment.

RESULTS

We observed a profound deactivation of limbic system components including hippocampus, hypothalamus, medio-orbitofrontal cortex and anterior cingulate cortex in subjects who reacted to the stressor with a significant increase of the endocrine stress marker cortisol. Further, in the fMRI study, the degree of deactivation in the hippocampus was correlated with the release of cortisol in response to the stress task.

CONCLUSIONS

The observed deactivation of limbic system structures suggests elevated activation at rest and during nonstressful situations. A model is proposed where the observed reduction in limbic system activity is essential for the initiation of the stress response.

An Electrophysiological Investigation of Semantic Incongruity Processing by People with Asperger’s Syndrome

The aim of this study was to investigate whether a physiological measure of impaired use of context could be obtained in people with Asperger's Syndrome (AS). The experimental paradigm employed was the use of electroencephalography to measure the detection of semantic incongruity within written sentences, as indexed by an N400 event-related potential. Whilst the seven controls appropriately demonstrated N400 potentials only to semantically incongruent stimuli, the seven participants with AS inappropriately demonstrated N400 potentials to congruent stimuli. These results are compatible with the possibility that the participants with AS did not use the context within sentences to predict the final word of the sentences.

Drawing on either side of the brain

Although both the cerebral laterality of processing visual information and human drawing skill have long been sources of investigation, there is not much empirical work combining the two. In this study, an attempt was made to explore if known different specialisations of the two cerebral hemispheres could help in predicting qualities of drawings produced by each hand. For this purpose, an amateur artist who is able to draw with either the left or the right hand produced a series of realistic drawings of 3D objects. Then 28 participants rated the drawings for several predetermined perceptual and aesthetic properties. The participants judged drawings made with the left hand as superior to those made with the right hand. Given that the right hemisphere controls the left hand, we suggest that this hand might also benefit from the more direct access to lateralised areas that are involved in the processing aspects of visual information and spatial properties (e.g., depth and shading). These perceptual processes may thus play an important role in the ability to draw realistic depictions of objects.

Calendrical savants: exceptionality and practice

The exceptionality of the skills of calendrical savants and the role of practice were investigated. Experiment 1 compared four autistic calendrical savants to Professor Conway, a distinguished mathematician with calendrical skills. Professor Conway answered questions over a greater range of years but some savants knew more calendrical regularities. Experiment 2 studied the development of a calendrical savant's ability to answer date questions for very remote future years. He started by making written calculations and progressed to mental calculation. His variation in response time for remote dates was similar to that for near dates. The findings are consistent with the view that calendrical savants develop their skills through practice.

CONCEPT FORMATION: 'OBJECT' ATTRIBUTES DYNAMICALLY INHIBITED FROM CONSCIOUS AWARENESS

We advance a dominant neural strategy for facilitating conceptual thought. Concepts are groupings of "object" attributes. Once the brain learns such critical groupings, the "object" attributes are inhibited from conscious awareness. We see the whole, not the parts. The details are inhibited when the concept network is activated, ie. the inhibition is dynamic and can be switched on and off. Autism is suggested to be the state of retarded concept formation. Our model predicts the possibility of accessing nonconscious information by artificially disinhibiting (turning off) the inhibiting networks associated with concept formation, using transcranial magnetic brain stimulation (TMS). For example, this opens the door for the restoration of perfect pitch, for recalling detail, for acquiring accent-free second languages beyond puberty, and even for enhancing creativity. The model further shows how unusual autistic savant skills as well as certain psychopathologies can be due respectively to privileged or inadvertent access to information that is normally inhibited from conscious awareness.

SAVANT-LIKE SKILLS EXPOSED IN NORMAL PEOPLE BY SUPPRESSING THE LEFT FRONTO-TEMPORAL LOBE

The astonishing skills of savants have been suggested to be latent in everyone, but are not normally accessible without a rare form of brain impairment. We attempted to simulate such brain impairment in healthy people by directing low-frequency magnetic pulses into the left fronto-temporal lobe. Significant stylistic changes in drawing were facilitated by the magnetic pulses in four of our 11 participants. Some of these "facilitated" participants also displayed enhanced proofreading ability. Our conclusions are derived from 11 right-handed male university students, eight of whom underwent placebo stimulation. We examined performance before, during and after exposure to the stimulation.

Das Savant-Syndrom: Eine Übersicht

Zusammenfassung. Theoretischer Hintergrund: Unter dem Savant-Syndrom versteht man das Auftreten eines herausragenden umschriebenen kognitiven Funktionsbereichs oder einer erstaunlichen Fertigkeit vorwiegend bei allgemeiner Intelligenzminderung. Fragestellung: Mit dieser Arbeit soll ein aktueller Überblick zur Beschreibung, Prävalenz, Neuropsychologie und Theoriebildung bezüglich des Syndroms gegeben werden. Methode: Auf der Basis historischer Berichte und derzeitiger empirischer Studien wird der Forschungsstand zum Savant-Phänomen dargestellt und diskutiert. Ergebnisse: Savants zeigen vor allem Kompetenzen in den Bereichen Gedächtnis, Musik, Zeichnen, Rechnen und Lesen. Spektakuläre Fälle dieser Inselbegabungen sind selten. Öfter anzutreffen sind Leistungen, die nur angesichts der vorherrschenden Psychopathologie der Person bemerkenswert sind. Savants sind unter autistisch beeinträchtigten Individuen vergleichbar häufig zu finden. Zum Verständnis der besonderen Fertigkeiten wurden in der Vergangenheit vielfältige, im Wesentlichen auf Fallstudien basierende Erklärungsansätze angeboten. Darunter die Involvierung von mechanischen Gedächtnisleistungen (rote memory), regelbasierten kognitiven Strategien, low-level-Informationsverarbeitung, repetitiv-übendem Verhalten, genetischen Faktoren und cerebralen Besonderheiten. Schlussfolgerungen: Angesichts der Heterogenität des Phänomens ist eine uneinheitliche Genese des Savant-Syndroms wahrscheinlich.

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.