Dopamine transporter genotype is associated with a lateralized resistance to distraction during attention selection.

Although lateral asymmetries in orienting behavior are evident across species and have been linked to interhemispheric asymmetries in dopamine signaling, the relative contribution of attentional versus motoric processes remains unclear. Here we took a cognitive genetic approach to adjudicate between roles for dopamine in attentional versus response selection. A sample of nonclinical adult humans (N = 518) performed three cognitive tasks (spatial attentional competition, spatial cueing, and flanker tasks) that varied in the degree to which they required participants to resolve attentional or response competition. All participants were genotyped for two putatively functional tandem repeat polymorphisms of the dopamine transporter gene (DAT1; SLC6A3), which are argued to influence the level of available synaptic dopamine and confer risk to disorders of inattention. DAT1 genotype modulated the task-specific effects of the various task-irrelevant stimuli across both the spatial competition and spatial cueing but not flanker tasks. Specifically, compared with individuals carrying one or two copies of the 10-repeat DAT1 allele, individuals without this allele demonstrated an immunity to distraction, such that response times were unaffected by increases in the number of distractor stimuli, particularly when these were presented predominantly in the left hemifield. All three genotype groups exhibited uniform costs of resolving leftward response selection in a standard flanker task. None of these significant effects could be explained by speed-accuracy trade-offs, suggesting that participants without the 10-repeat allele of the DAT1 tandem repeat polymorphism possess an enhanced attentional ability to suppress task-irrelevant stimuli in the left hemifield.

An association between a dopamine transporter gene (SLC6A3) haplotype and ADHD symptom measures in nonclinical adults.

Previous genetic studies have postulated that attention deficit hyperactivity disorder (ADHD) should be regarded as the extreme end of a set of behavioural traits that can be continuously measured in the general population. The current study adopted a quantitative trait approach to examine the relationship between dopamine gene variants and self-reported ADHD symptoms in 517 nonclinical adults. Although genetic associations with variants of both the dopamine transporter (DAT1; SLC6A3) and D4 receptor (DRD4) genes have been reliably reported in children, results in adults are less consistent. We probed two potentially functional variable number of tandem repeat (VNTR) polymorphisms in the 3'UTR and intron 8 of DAT1, the 10-repeat and 6-repeat alleles of which respectively form a haplotype (10/6 DAT1 haplotype) that is associated with childhood ADHD. We also genotyped the exon 3 VNTR of DRD4, the 7-repeat allele of which is also an established risk factor for childhood ADHD. Permutation analysis showed an influence of the 10/6 DAT1 haplotype on both CAARS-G and CAARS-H (DSM-IV ADHD Symptoms Total and ADHD Index respectively), such that ADHD symptom scores increased with each additional copy of the 10/6 DAT1 haplotype. This result survived corrections for multiple comparisons both at the level of genotype and phenotype. A nominal association with CAARS-G was also found for the 7-repeat allele of the DRD4 VNTR however this did not survive multiple comparison correction. Our results provide further support for the influence of variation in the 10/6 DAT1 haplotype and individual differences in ADHD symptoms in adults.

Functional play in young children with autism and Williams syndrome: A cross-syndrome comparison.

Functional play during early childhood paves the way to symbolic play and social communicative skills. However, functional play is surprisingly understudied in children with developmental disorders affecting social and communicative domains, such as Autism Spectrum Disorder (ASD) and Williams syndrome (WS). To address this issue and to evaluate both the quantity and quality of functional play in children with ASD and WS, we examined different play types using fine grained behavioral analysis with a group of age and IQ-matched developmentally delayed children with ASD (n = 14) and WS (n = 14) in comparison with 12 age-matched typically developing (TD) children. Significant differences were found in the quantity of functional play in the ASD and WS groups compared to TD children, with a limited breadth of object exploration found in children with ASD. While TD children engaged more frequently in functional versus nonfunctional play, this was not the case for children with ASD and WS, who showed the same amount of functional and nonfunctional play. Furthermore, functional play behavior was associated with intellectual and adaptive function in children with WS, but not ASD. These results point to the importance of intervention strategies that focus on functional play in improving developmental outcomes for children with ASD and WS.

Delineation of a spatial working memory profile using a non-verbal eye-tracking paradigm in young children with autism and Williams syndrome.

Working memory deficits profoundly inhibit children's ability to learn. While deficits have been identified in disorders such as autism spectrum disorder (ASD) and Williams syndrome (WS), findings are equivocal, and very little is known about the nature of these deficits early in development. A major barrier to advances in this area is the availability of tasks suitable for young children with neurodevelopmental disorders who experience difficulties with following verbal instructions or who are distressed by formal testing demands. To address these issues, a novel eye-tracking paradigm was designed based on an adaptation of the classic A not B paradigm in order to examine the early foundations of spatial working memory capabilities in 26 developmentally delayed preschool children with ASD, 18 age- and IQ-matched children with WS, and 19 age-matched typically-developing (TD) children. The results revealed evidence that foundational spatial working memory performance in ASD and WS was comparable with that of TD children. Performance was associated with intellectual ability in the ASD and TD groups, but not in the WS group. Performance was not associated with adaptive behavior in any group. These findings are discussed in the context of previous research that has been largely limited to older and substantially less developmentally delayed children with these neurodevelopmental disorders.

Reduced Motor Interference in Preschoolers with Autism Spectrum Disorder and Williams Syndrome.

Motor interference occurs when action execution is hindered by the observation of an incongruent action. The present study used a novel eye-tracking paradigm to test the motor interference effect in 22 preschoolers with autism spectrum disorder (ASD), 14 preschoolers with Williams syndrome (WS), and 18 typically developing (TD) peers. In TD children, performance of a pre-determined action was slower after the observation of an incongruent motor action and faster following observation of a congruent motor action, indicating a motor interference effect. In both the ASD and WS groups, performance was unaffected by the congruent versus incongruent nature of the observed motor action.

Attention to novelty versus repetition: Contrasting habituation profiles in Autism and Williams syndrome.

BACKGROUND: Abnormalities in habituation have been documented in Autism Spectrum Disorder (ASD) and Williams syndrome (WS). Such abnormalities have been proposed to underlie the distinctive social and non-social difficulties that define ASD, including sensory features and repetitive behaviours, and the distinctive social phenotype characterizing WS. METHODS: We measured habituation in 39 preschoolers with ASD, 20 peers with WS and 19 typically developing (TD) children using an eye-tracking protocol that measured participants' duration of attention in response to a repeating stimulus and a novel stimulus presented side by side across multiple trials. RESULTS: Participants in the TD group and the WS group decreased their attention toward the repeating stimulus and increased their attention to the novel stimulus over time. Conversely, the ASD group showed a similar attentional response to the novel and repeating stimuli. Habituation was correlated with social functioning in the WS but not in the ASD group. Contrary to predictions, slower habituation in ASD was associated with lower severity of repetitive behaviours. CONCLUSIONS: Habituation appears to be intact in WS and impaired in ASD. More research is needed to clarify the nature of the syndrome-specific patterns of correlations between habituation and social and non-social functioning in these neurodevelopmental disorders.

The social nature of overimitation: Insights from Autism and Williams syndrome.

When imitating novel actions, typically developing preschoolers often copy components of the demonstration that are unrelated to the modeled action's goal, a phenomenon known as 'overimitation'. According to the social motivation account, overimitation fulfills social affiliation motives (i.e., the imitator's drive to experience social connectedness with the demonstrator and the social context). Conversely, according to the social-cognitive account, overimitation reflects overattribution of causal relevance (i.e., the imitator's failure to appreciate that some components of the demonstration are not relevant to the action's outcome). Autism Spectrum Disorder (ASD) and William syndrome (WS) are characterized by reduced and enhanced spontaneous social motivation, respectively, as well as similar impairments in social-cognition, thus providing helpful test cases to understand the nature of overimitation. Using a novel eye-tracking paradigm, we examined overimitation in 31 preschoolers with ASD, 18 age- and IQ-matched peers with WS, and 19 age-matched typically developing children. We found that children with WS and typically developing children were more likely to overimitate, and to increase their attention to the model's face during demonstration of causally irrelevant actions, compared to those with ASD. These findings will be discussed in the context of support for the social-motivational account of overimitation.

Social Attention, Joint Attention and Sustained Attention in Autism Spectrum Disorder and Williams Syndrome: Convergences and Divergences.

There is limited knowledge on shared and syndrome-specific attentional profiles in autism spectrum disorder (ASD) and Williams syndrome (WS). Using eye-tracking, we examined attentional profiles of 35 preschoolers with ASD, 22 preschoolers with WS and 20 typically developing children across social and non-social dimensions of attention. Children with ASD and those with WS presented with overlapping deficits in spontaneous visual engagement with the target of others' attention and in sustained attention. Children with ASD showed syndrome-specific abnormalities in monitoring and following a person's referential gaze, as well as a lack of preferential attention to social stimuli. Children with ASD and WS present with shared as well as syndrome-specific abnormalities across social and non-social dimensions of attention.

Social affiliation motives modulate spontaneous learning in Williams syndrome but not in autism.

BACKGROUND: Children with autism spectrum disorder (ASD) and those with Williams syndrome (WS) have difficulties with learning, though the nature of these remains unclear. METHODS: In this study, we used novel eye-tracking and behavioral paradigms to measure how 36 preschoolers with ASD and 21 age- and IQ-matched peers with WS attend to and learn novel behaviors (1) from the outcomes of their own actions (non-social learning), (2) through imitation of others' actions (social learning), and across situations in which imitative learning served either an instrumental function or fulfilled social affiliation motives. RESULTS: The two groups demonstrated similar abilities to learn from the consequences of their own actions and to imitate new actions that were instrumental to the achievement of a tangible goal. Children with WS, unlike those with ASD, increased their attention and imitative learning performance when the model acted in a socially engaging manner. CONCLUSIONS: Learning abnormalities in ASD appear to be linked to the social rather than instrumental dimensions of learning.

Verbal labels increase the salience of novel objects for preschoolers with typical development and Williams syndrome, but not in autism.

BACKGROUND: Early research has documented that young children show an increased interest toward objects that are verbally labeled by an adult, compared to objects that are presented without a label. It is unclear whether the same phenomenon occurs in neurodevelopmental disorders affecting social development, such as autism spectrum disorder (ASD) and Williams syndrome (WS). METHODS: The present study used a novel eye-tracking paradigm to determine whether hearing a verbal label increases the salience of novel objects in 35 preschoolers with ASD, 18 preschoolers with WS, and 20 typically developing peers. RESULTS: We found that typically developing children and those with WS, but not those with ASD, spent significantly more time looking at objects that are verbally labeled by an adult, compared to objects that are presented without a label. CONCLUSIONS: In children without ASD, information accompanied by the speaker's verbal label is accorded a "special status," and it is more likely to be attended to. In contrast, children with ASD do not appear to attribute a special salience to labeled objects compared to non-labeled objects. This result is consistent with the notion that reduced responsivity to pedagogical cues hinders social learning in young children with ASD.