Elsevier

Research in Autism Spectrum Disorders

Volume 4, Issue 4, October–December 2010, Pages 555-564
Research in Autism Spectrum Disorders

The neurobiology of autism: Theoretical applications

https://doi.org/10.1016/j.rasd.2010.01.004Get rights and content

Abstract

Autism spectrum disorders (ASD) are complex neurological disorders characterized by heterogeneity in skills and impairments. A variety of models have been developed to describe the disorders and a wide range of brain processes have been implicated. This review attempts to integrate some of the consistent neurological findings in the research with three of the dominant models of core deficits of ASDs: the weak central coherence model, the theory of mind model, and the mirror neuron system model. A review of the literature suggests that the cerebellum and the frontal lobes may be implicated in all three of the models, while the temporal lobe is associated with the theory of mind model and the mirror neuron model. In particular, the theory of mind model and the mirror neuron system model both implicate the inferior frontal gyrus and the superior temporal sulcus. This review indicates that each model appears to be heavily substantiated by neurological research, suggesting that each may capture important aspects of ASDs.

Section snippets

Etiology of autism

The etiology of ASDs is complex and has been associated with genes, neurological pathways, neurotransmitters, and environmental influences. Although etiologies have not been firmly established in the majority of cases, it is of interest to review possible causal factors to understand the incidence and prevalence of the spectrum of outcomes.

Weak central coherence model

The weak central coherence (WCC) model, originally proposed by Frith and Happé (1994), asserts that autism is characterized by a cognitive bias towards local processing over global processing. As a result, individuals with autism fail to automatically use context to aid in understanding their environment. Evidence for this theory includes the enhanced performance of individuals with autism on block design tasks, embedded-figures tasks, and several illusions that involve the influence of context

Cerebellum: function

While the cerebellum is known to regulate sequenced movement, research in the past few decades has emphasized the importance of the cerebellum in a wide variety of psychological functions (for reviews see Katz and Steinmetz, 2002, Schmahmann, 1997). Some of these functions include: procedural learning, emotion, thought, and attention (Allen and Courchesne, 2003, Courchesne et al., 1995). In particular, it appears to be implicated in attention shifting (Iarocci & McDonald, 2006). The cerebellum

Frontal lobe: function

The frontal lobe is central to many functions that may be implicated in autism. The prefrontal cortex is involved in executive functioning with respect to working memory, inhibition, planning, organization, set shifting, cognitive flexibility, orienting, and disengaging attention, all of which appear to be deficient among individuals with ASDs (Hughes et al., 1994, Ozonoff et al., 1991). Also, 40–70% of individuals with ASDs exhibit higher order cognitive impairment, suggesting that the frontal

Temporal lobe: function

The functions of the temporal lobe are numerous and include audition, memory, and object perception, as well as functions that may be affected in individuals with autism. The temporal lobe is associated with receptive language, particularly because it includes Wernickes's area (Wernicke, 1874). The temporal lobe also appears to be involved in many of the functions that can be considered part of social cognition: joint attention, action observation, and empathy (Schultz, 2005). Finally, it

Other brain regions

Converging evidence suggests that deficits in parts of the cerebellum, frontal lobes, and temporal lobes are implicated in the development of ASDs; however, reviews of the literature suggest that impairments in several other brain areas may also be involved. Parts of the parietal lobe may be implicated in deficits in the mirror neuron system of individuals with autism, particularly in challenges with action imitation (Hadjikhani et al., 2006, Williams et al., 2006; for reviews see Oberman and

Models

With a better understanding of some of the neural mechanisms underlying autism, it is now possible to re-evaluate the major theories of autism, in light of this research (summarized in Table 2).

The weak central coherence model predicts deficits in the cerebellum, and possibly in the frontal lobes and the corpus callosum among individuals with ASDs. A substantial amount of research implicates the cerebellum and the frontal lobes, while fewer studies implicate the corpus callosum. The theory of

Challenges in research

One of the major challenges in autism research is the heterogeneity of the causes, symptoms, severity, and labels for the disorder. Descriptions of samples range from “pure” autism, through ASD, and pervasive developmental disorder (PDD), which encompasses a large range of deficits. This range makes it difficult to generalize across studies in which the samples may be quite different (Bebko et al., 2008). In addition, co-morbidities such as cognitive impairment, seizure disorders, and

Future directions

Based on the previous section, it is clear that there are gaps in the autism research literature. With regard to the issue of age, research should continue to examine at-risk children (siblings of individuals with autism) longitudinally, tracking their neurological development from shortly after birth to see if they develop autism. Given the challenges of running fMRI and PET research with younger children, more EEG/ERP studies need to be conducted with infants and young children because these

Acknowledgement

Schroeder was supported during the preparation of this manuscript as a trainee through the Canadian Institutes of Health Research-National Alliance for Autism Research (CIHR-NAAR) Autism Spectrum Disorders Strategic Training Program (PI:JHH) & Canadian Institutes of Health Research-Canadian Graduate Scholarship. Cappadocia was supported through Social Sciences and Humanities Research Council and Ontario Graduate Scholarship. Bebko and Desrocher were each supported through Canadian Institutes of

References (48)

  • L.M. Oberman et al.

    EEG evidence for mirror neuron dysfunction in autism spectrum disorders

    Cognitive Brain Research

    (2005)
  • G. Rizzolatti et al.

    Premotor cortex and the recognition of motor actions

    Cognitive Brain Research

    (1996)
  • R. Schultz

    Developmental deficits in social perception in autism: The role of the amygdala and fusiform face area

    International Journal of Developmental Neuroscience

    (2005)
  • J.H.G. Williams et al.

    Neural mechanisms of imitation and ‘mirror neuron’ functioning in autistic spectrum disorder

    Neuropsychologia

    (2006)
  • M. Zilbovicius et al.

    Autism, the superior temporal sulcus and social perception

    Trends in Neuroscience

    (2006)
  • G. Allen et al.

    Differential effects on developmental Cerebellar abnormality on cognitive and motor functions in the Cerebellum: An fMRI study of autism

    American Journal of Psychiatry

    (2003)
  • S.W. Anderson et al.

    Impairment of social and moral behavior related to early damage in human prefrontal cortex

    Nature Neuroscience

    (1999)
  • S. Baron-Cohen et al.

    Social intelligence in the normal and autistic brain: An fMRI study

    European Journal of Neuroscience

    (1999)
  • R. Beaumont et al.

    Theory of mind and central coherence in adults with high-functioning autism or Asperger syndrome

    Autism

    (2006)
  • E.D. Bigler et al.

    Superior temporal gyrus, language function, and autism

    Developmental Neuropsychology

    (2007)
  • P. Broca

    Remarques sur le siège de la faculté du langagé articule, suivies d’une observation d’aphémie

    Bulletin et Mémoires de la Société Anatomique de Paris

    (1861)
  • R.A. Carper et al.

    Inverse correlation between frontal lobe and cerebellum sizes in children with autism

    Brain

    (2000)
  • A.E. Chudley

    Genetic landmarks through philately-autism spectrum disorders: A genetic update

    Clinical Genetics

    (2004)
  • E. Courchesne et al.

    Neurodevelopmental principles guide research on developmental psychopathologies

  • Cited by (25)

    • Fuzzy Synchronization Likelihood-wavelet methodology for diagnosis of autism spectrum disorder

      2012, Journal of Neuroscience Methods
      Citation Excerpt :

      Autism is a complex behavioral, cognitive and developmental brain disorder, originally described in 1940s (Belmonte et al., 2004; Verhoeven et al., 2010). It is characterized by social impairments, deficits in communication, and restricted and repetitive behavior (Rippon et al., 2007; Schroeder et al., 2010). These symptoms begin normally before a child is about three (2–4) years old (Courchesne et al., 2004; Redcay and Courchesne, 2005; Klin et al., 2009).

    • Autism diagnosis and screening: Factors to consider in differential diagnosis

      2012, Research in Autism Spectrum Disorders
      Citation Excerpt :

      We argue that with respect to the assessment and diagnosis of autism, no such gold standard exists, nor is one particular measure likely to emerge in the foreseeable future. Also, despite the notion that autism has a neurodevelopmental cause, diagnosis is at this point based solely on observable behaviors (Brown, Ouellette-Kuntz, Hunter, & Kelley, 2010; Clifford, Hudry, Brown, Pasco, & Charman, 2010; Nydén et al., 2010a, 2010b; Schroeder et al., 2010). As a result, diagnosis is typically accomplished through observation of the child, interview of one or more caregivers, typically involving one or more tests of core symptoms of autism with established reliability and validity, and review of client history.

    • Defining the cognitive phenotype of autism

      2011, Brain Research
      Citation Excerpt :

      There is increasing evidence that multiple aetiologies may converge to disrupt the development and function of several brain systems that are implicated in the social and non-social behaviours that define ASDs (Happé and Ronald, 2008; Schroeder et al., 2010), including the frontal and temporal neocortex, the caudate, and the cerebellum (Abrahams and Geschwind, 2010).

    View all citing articles on Scopus
    View full text