Attentional Mechanisms in Autism, ADHD, and Autism-ADHD Using a Local-Global Paradigm.

OBJECTIVE: Cognitive flexibility or attentional set-shifting capacity has long been considered a core area of executive dysfunction for individuals with autism. Whether these difficulties are due to higher-level attentional difficulties associated with comorbid ADHD remains unclear. METHOD: The current study compared the performance of 48 participants with autism, ADHD, autism-ADHD, and a comparison group ( N = 12 per group) on a set-shifting task, which included a local-global paradigm. RESULTS: Results of this study revealed that participants with attentional difficulties (autism + ADHD and ADHD alone) exhibited a significant shifting cost (difference between maintaining and shifting attention). CONCLUSION: Attentional difficulties associated with ADHD may be associated with an enhanced attentional shifting cost. Implications of these results were discussed in relation to screening for ADHD symptoms in studies of individuals with autism which seek to determine the neuropsychological profile of this condition.

Exploring factors related to the anger superiority effect in children with Autism Spectrum Disorder.

Despite face and emotion recognition deficits, individuals with Autism Spectrum Disorder (ASD) appear to experience the anger superiority effect, where an angry face in a crowd is detected faster than a neutral face. This study extended past research to examine the impacts of ecologically valid photographic stimuli, gender and anxiety symptoms on the anger superiority effect in children with and without ASD. Participants were 81, 7-12year old children, 42 with ASD matched on age, gender and perceptual IQ to 39 typically developing (TYP) children. The photographic stimuli did not impact on task performance in ASD with both groups exhibiting the anger superiority effect. There were no gender differences and no associations with anxiety. Age was associated with the effect in the TYP but not ASD group. These findings confirm a robust effect of speeded detection of threat in ASD which does not appear to be confounded by gender or anxiety, but may have different underlying age-associated mechanisms.

Parent-Child Agreement Using the Spence Children's Anxiety Scale and a Thermometer in Children with Autism Spectrum Disorder.

Children with Autism Spectrum Disorder (ASD) experience high anxiety which often prompts clinical referral and requires intervention. This study aimed to compare parent and child reports on the Spence Children's Anxiety Scale (SCAS) and a child-reported "worry thermometer" in 88 children aged 8-13 years, 44 with ASD and 44 age, gender, and perceptual IQ matched typically developing children. There were no gender differences in child report on the SCAS and worry thermometers. Results indicated generally good correlations between parent and child self-reported SCAS symptoms for typically developing children but poor agreement in parent-child ASD dyads. The worry thermometer child-report did not reflect child or parent reports on the SCAS. Findings suggest 8-13-year-old children with ASD may have difficulties accurately reporting their anxiety levels. The clinical implications were discussed.

Saccade adaptation in autism and Asperger's disorder.

Autism and Asperger's disorder (AD) are neurodevelopmental disorders primarily characterized by deficits in social interaction and communication, however motor coordination deficits are increasingly recognized as a prevalent feature of these conditions. Although it has been proposed that children with autism and AD may have difficulty utilizing visual feedback during motor learning tasks, this has not been directly examined. Significantly, changes within the cerebellum, which is implicated in motor learning, are known to be more pronounced in autism compared to AD. We used the classic double-step saccade adaptation paradigm, known to depend on cerebellar integrity, to investigate differences in motor learning and the use of visual feedback in children aged 9-14 years with high-functioning autism (HFA; IQ>80; n=10) and AD (n=13). Performance was compared to age and IQ matched typically developing children (n=12). Both HFA and AD groups successfully adapted the gain of their saccades in response to perceived visual error, however the time course for adaptation was prolonged in the HFA group. While a shift in saccade dynamics typically occurs during adaptation, we revealed aberrant changes in both HFA and AD groups. This study contributes to a growing body of evidence centrally implicating the cerebellum in ocular motor dysfunction in autism. Specifically, these findings collectively imply functional impairment of the cerebellar network and its inflow and outflow tracts that underpin saccade adaptation, with greater disturbance in HFA compared to AD.

Gait adaptation during obstacle crossing reveals impairments in the visual control of locomotion in Williams syndrome.

Recent evidence indicates that individuals with Williams syndrome (WS), a rare genetically based neurodevelopmental disorder, show abnormalities of parietal and cerebellar regions of the brain that may be involved in the visual control of locomotion. Here we examined whether parietal and cerebellar abnormalities contribute to deficits in spatiotemporal characteristics and foot placement variability during obstacle crossing in adults with WS, when compared with an IQ-matched group of adults with Down syndrome (DS) and typically developing adult controls. We used the GAITRite walkway to examine the spatiotemporal characteristics and foot placement variability relative to a small ground-based obstacle in the travel path. We found that adults with WS showed late adjustments to spatiotemporal gait characteristics alongside an exaggerated and more spatially constrained visual guidance of foot positioning in the final steps prior to stepping over the obstacle. In contrast, the adults with DS showed longer step duration and more variable step length and step duration during the crossing and recovery steps after the obstacle, suggestive of cerebellar dysfunction. Although the controls were able to reduce the variability of foot placement across the obstacle crossing trials, both the WS and DS groups did not become more consistent with practice. These findings indicate a less flexible and overly constrained visuomotor system in WS, which is consistent with more widespread and diffuse abnormalities in parietal and cerebellar regions.

Right parietal dysfunction in children with attention deficit hyperactivity disorder, combined type: a functional MRI study.

Attention deficit hyperactivity disorder, combined type (ADHD-CT) is associated with spatial working memory deficits. These deficits are known to be subserved by dysfunction of neural circuits involving right prefrontal, striatal and parietal brain regions. This study determines whether decreased right prefrontal, striatal and parietal activation with a mental rotation task shown in adolescents with ADHD-CT is also evident in children with ADHD-CT. A cross-sectional study of 12 pre-pubertal, right-handed, 8-12-year-old boys with ADHD-CT and 12 pre-pubertal, right-handed, performance IQ-matched, 8-12-year-old healthy boys, recruited from local primary schools, was completed. Participants underwent functional magnetic resonance imaging while performing a mental rotation task that requires spatial working memory. The two groups did not differ in their accuracy or response times for the mental rotation task. The ADHD-CT group showed significantly less activation in right parieto-occipital areas (cuneus and precuneus, BA 19), the right inferior parietal lobe (BA 40) and the right caudate nucleus. Our findings with a child cohort confirm previous reports of right striatal-parietal dysfunction in adolescents with ADHD-CT. This dysfunction suggests a widespread maturational deficit that may be developmental stage independent.

A deficit in shifting attention present in high-functioning autism but not Asperger's disorder.

The aim of this study was to examine executive functioning, in particular, attentional set-shifting deficits in high-functioning autism (n = 12) and Asperger's disorder (n = 12). A large or global digit composed of smaller or local digits was presented during each trial. The participants indicated the presence of 1s or 2s by pressing the appropriate button. These targets could appear globally or locally Relative to IQ, sex and age matched controls, reaction time to global targets in individuals with autism was retarded when the previous target appeared locally. This deficiency in shifting from local to global processing, however, was not observed in individuals with Asperger's disorder. The theoretical and neurobiological significance of this dissociation in executive functioning in these clinically related disorders was explored.

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.

Atypical interference of local detail on global processing in high-functioning autism and Asperger's disorder.

This study explored the claim that individuals with autism and Asperger's disorder tend to process locally rather than holistically. Participants observed a large or "global" number composed of smaller or "local" numbers. The response was contingent upon the identification of either the large stimulus or the small stimuli. Relative to age, sex, and IQ matched controls, global processing in children and adolescents with autism (N = 12) and Asperger's disorder (N = 12) was more vulnerable when the local stimuli were incongruent. The autism group made more global errors than their matched control group, regardless of whether there was local incongruence. In contrast, the Asperger's disorder group made a similar number of global errors as their respective control group. These results were discussed in relation to an "absence of global precedence" notion, "weak central coherence" theory, and right-hemisphere dysfunction. The neurobiological significance of these findings were discussed in the context of a fronto-striatal model of dysfunction.