sample Cerebellar dysfunction , cognitive flexibility and autistic traits in a non-clinical

A D D R E S S Correspondence should be addressed to: N I C O L E R I D L E Y , Department of Psychology, Macquarie University, NSW 2109,Australia. Email: nicole.ridley@students. mq.edu. au Several sets of data suggest motor problems are present in individuals with autism spectrum disorders (ASD), to the extent that Rinehart and McGinley (2010) suggested that motor dysfunction may be considered a core feature of ASD. Retrospective analyses of children diagnosed with ASD indicate that motor abnormalities are commonly present during the first year of the K E Y W O R D S cerebellum, autistic traits, AQ, cognitive flexibility, autismspectrum quotient 728 Copyright © The Author(s), 2011. Reprints and permissions: http://www.sagepub. co.uk/journalspermissions.nav DOI: 10.1177/1362361310395956 at Univ. of Tasmania Library on August 31, 2014 aut.sagepub. com Downloaded from CEREBELLAR DYSFUNCTION, COGNITIVE FLEXIBILITY AND AUTISTIC TRAITS 729 child’s life, before even linguistic and social difficulties have emerged (Nayate et al., 2005). Children (four to nine years of age) with a diagnosis of, or at risk for, ASD have been found to have significantly poorer performance on the Movement Assessment Battery for Children than age-matched controls, although the apparent non-linear trajectory of motor development in children complicates cross-sectional comparisons (Van Waelvelde et al., 2010). A qualitative neurological assessment of adults with autism by Hallett et al. (1993) revealed irregular gait in four of the five participants, whilst difficulties in the accuracy and timing of movements and with posture and gait have likewise been noted in adults and children with ASD (Minshew et al., 2004; Rinehart et al., 2006a,b). However, the origin of any motor dysfunction remains unclear. Rinehart et al. (2006a,b) propose that it is likely that both fronto-striatal and cerebellar involvement contribute to the motor symptoms of autism, with basal ganglia integrity crucial to the initiation and mediation of movements as well as postural formation, and cerebellar function central to the control and refinement of end-stage movement, with cerebellar lesions resulting in inaccurate, irregular and variable movements. Their analysis of gait disturbances in children with ASD suggested that cerebellar dysfunction is qualitatively distinguishable in ASD, with greater difficulty walking in a straight line, reduced stride regularity, less coordination and reduced smoothness relative to the comparison group. Further support for the link between cerebellar abnormality and the motor impairment in autism is provided by functional imaging studies which have reported abnormal and more extensive patterns of cerebellar activation in autistic subjects than in neurotypicals during simple motor tasks and motor learning exercises (Allen et al., 2004; Mueller et al., 2003). The hypothesis that motor problems described in ASD arise from cerebellar dysfunction is consistent with the larger body of work showing abnormalities in cerebellar structure or function in ASD (e.g., Allen et al., 2004; Bauman and Kemper, 2005; Rinehart et al., 2006c; Wegiel et al., 2010). Anatomical links between the cerebellum and frontal lobe are now being described (e.g., Krienen and Buckner, 2009) so it is not surprising that the literature suggests a possible role of the cerebellum in cognitive and executive function (Durisko and Fiez, 2010; Schmahmann and Sherman, 1997). Impairment in the area of ‘executive functions’ has been frequently reported in individuals with ASD, particularly in the domain of ‘set-shifting’, a term used interchangeably with cognitive flexibility in executive function research. Perseverative responding on the Wisconsin Card Sorting Test by individuals with autism has been repeatedly demonstrated (Rumsey and Hamburger, 1988; South et al., 2007), along with impairments on other setshifting tasks, including Intradimensional/Extradimensional shifting tasks (Yerys et al., 2009), visual attention switching tasks such as the Trail Making at Univ. of Tasmania Library on August 31, 2014 aut.sagepub. com Downloaded from Task (Goldstein et al., 2001) and poorer performance on verbal fluency switching tasks (Kleinhans et al., 2005). Such impairment in cognitive flexibility has been suggested to play a key role in the manifestation of the limited and repetitive behaviours seen in autism, with Lopez et al. (2005) initially describing a direct relationship between measures of cognitive flexibility and of the restricted and repetitive behaviours in ASD. More recently, South et al. (2007) also found a significant positive relationship between scores on the stereotyped behaviour subscale of the Autism Diagnostic Interview-Revised Battery and perseverative responses on the Wisconsin Card Sorting Test (WCST). Whilst set-shifting impairment remains the most consistently reported executive function deficit in ASD research, deficits in other domains such as response inhibition and working memory are less frequently reported, with the majority of literature suggesting that these may remain relatively spared in ASD (Kleinhans et al., 2005; Ozonoff and Jensen, 1999). The literature is less consistent on fluency and generativity tasks, with several studies reporting impaired verbal fluency abilities in individuals with ASD and others reporting no differences on non-verbal (design fluency) and verbal (letter and semantic fluency) measures (see Lopez et al., 2005). Kleinhans et al. (2005) proposed that verbal tasks that require generation of efficient cognitive search strategies and problem-techniques, such as verbal switching and letter fluency, best indicate fluency deficits in high-functioning ASD. One area of increasing interest in the literature is the form of repetitive behaviours in high-functioning individuals with ASD. An analysis by South et al. (2005) suggested that in disorders such as Asperger’s syndrome (AS) and high-functioning autism (HFA) repetitive behaviour usually manifests as excessive circumscribed interests, or areas of intense interest. These interests are likely to have a systems focus, such as mechanical properties of objects, physics, mathematics or categories in the natural environment, rather than being person-oriented in nature (Baron-Cohen and Wheelwright, 1999). Proponents of the ‘weak central coherence’ theory suggest that this obsession with systems is a function of a style of processing which involves a deficit in the ability to process information into a meaningful whole but preserved ability to focus on detail (Happe and Frith, 2006). This local processing bias may represent more of a talent than a disability in domains that require a thorough understanding of the mechanisms of systems. If, as Frith (2003), suggests, high intelligence can camouflage problems with social communication, individuals at the higher end of the spectrum may potentially be able to hide their social deficits and reduce or restrict social interaction and make use of their strengths in system analysis. A bias for local processing has also been found in relatives of individuals with ASD (Baron-Cohen, 2002), providing support for a ‘subclinical’ A U T I S M 15(6)