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Recent debates in the literature discuss commonalities between Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) at multiple levels of putative causal networks. This debate requires systematic comparisons between these disorders that have been studied in isolation in the past, employing potential markers of each disorder to be investigated in tandem. The present study, choose superior local processing, typical to ASD, and increased Intra-Subject Variability (ISV), typical to ADHD, for a head-to-head comparison of the two disorders, while also considering the comorbid cases. It directly examined groups of participants aged 10–13 years with ADHD, ASD with (ASD+) or without (ASD−) comorbid ADHD and a typically developing (TD) group (total N = 85). A visual search task consisting of an array of paired words was designed. The participants needed to find the specific pair of words, where the first word in the pair was the cue word. This visual search task was selected to compare these groups on overall search performance and trial-to-trial variability of search performance (i.e., ISV). Additionally, scanpath analysis was also carried out using Recurrence Quantification Analysis (RQA) and the Multi-Match Model. Results show that only the ASD− group exhibited superior search performance; whereas, only the groups with ADHD symptoms showed increased ISV. These findings point towards a double dissociation between ASD and ADHD, and argue against an overlap between ASD and ADHD. [ABSTRACT FROM AUTHOR]

Recent discussions in the literature, along with the revision of the Diagnostic and Statistical Manual (DSM) (American Psychiatric Association 2013), suggest aetiological commonalities between the highly comorbid Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD). Addressing this discussion requires studying these disorders together by comparing constructs typical to each of them. In the present study, we investigate global processing, known to be difficult for participants with ASD, and Intra-Subject Variability (ISV), known to be consistently increased in participants with ADHD, in groups, aged 10–13 years, with ADHD (n = 25), ASD without comorbid ADHD (ASD-) (n = 13) and ASD with ADHD (ASD+) (n = 18) in comparison with a typically developing group (n = 22). A Copying task, typically requiring global processing and in this case particularly designed using equally complex stimuli to also measure ISV across trials, was selected. Oculomotor measures in this task proved to be particularly sensitive to group differences. While increased ISV was not observed in the present task in participants with ADHD, both ASD groups looked longer on the figure to be drawn, indicating that global processing takes longer in ASD. However, the ASD+ group fixated on the figure only between drawing movements, whereas the ASD- group did this throughout the drawing process. The present study provides evidence towards ASD and ADHD being separate, not-overlapping, disorders. Since the pure ASD- group was affected more by central coherence problems than the ASD+ group, it may suggest that neuropsychological constructs interact differently in different clinical groups and sub-groups. [ABSTRACT FROM AUTHOR]

A flickering light can be seen during a saccadic eye movement as a pattern of contours known as a phantom array. On repeated pairs of trials, observers made saccades across a narrow (1 arc minutes), bright (10−4 cd/m2) source of flickering light and were required to detect the phantom array. On one of each pair of trials, chosen at random, the light flickered at 60 kHz and on the other at a frequency chosen in the range 1–11 kHz. In two such studies, a few observers were reliably able to discriminate 11 kHz from 60 kHz on the basis of the visibility of the phantom array. The average threshold at which the array was visible was about 6 kHz and therefore double that previously obtained with larger targets. Those observers who were able to see the phantom array tended reliably to report more symptoms of visual discomfort in everyday life. [ABSTRACT FROM AUTHOR]

Human saccades and fixations have numerous functions in complex everyday tasks, which have sometimes been neglected in simple experimental situations. In this review I describe some of the characteristics of eye movement behaviour during real-world interactions with objects, while walking in natural environments and while holding a conversation. When performing real-world actions and walking around the world, we fixate relevant features at critical time points during the task. The eye movements between these fixations are planned and coordinated alongside head and body movements, often occurring a short time before the corresponding action. In social interactions, eye movements are both a mechanism for taking in information (for example, when looking at someone's face or following their gaze) and for signalling one's attention to another person. Thus eye movements are specific to a particular task context and subject to high-level planning and control during everyday actions. [ABSTRACT FROM AUTHOR]

Avoiding distractors is crucial for our daily lives. Load theory argues that high perceptual load facilitates distractor avoidance, while high cognitive load impedes distractor avoidance (see, Lavie, 2005). Difficulty in avoiding distractors is one of the key symptoms of Attention Deficit/Hyperactivity Disorder (ADHD; APA, 2013). In a series of experiments, we investigated visual attention during the viewing of complex scenes (featuring social and non-social objects), while manipulating Working Memory Load (WM) in a concurrent task. We also explored the relationship between these tasks and ADHD-like traits. Fixations during scene viewing were investigated with reference to objects of high and low saliency with social area (a person) also imbedded in the image. We tested the hypothesis that high WM load would lead to increased capture by the salient distractor. In contrast, attending to the social item might require more top-down resources and so be disrupted by WM load. The pattern of results suggests that during image viewing the social object was fixated to a greater degree than the other object (regardless of salience). While, there was a relationship between the degree of ADHD-like traits and performance on the memory task, WM load did not seem to affect scanning in scenes. Such findings suggest that top-down resources are not needed to attend to a social area in complex stimuli. [ABSTRACT FROM AUTHOR]

Background: Endophenotypes are intermediate variables in the hypothetical causal chain from observed behavior of a clinical disorder to its underlying genotype. Recent literature trends point to the potential etiological overlap between Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD). The present study aims to systematically compare these groups, by studying the potential endophenotypes of ASD (local-global processing; social cueing) and ADHD (Intra-Subject Variability (ISV)) in tandem. Methods: Three tasks, namely visual search, copying down and gaze cueing were administered to directly examine ASD- (ASD without co-morbid ADHD), ADHD and ASD+ (ASD with co-morbid ADHD) groups, in comparison to a typically developing (TD) group (N=100). Step-by-step process analysis and scan-path models were employed to analyze the oculomotor and behavioural data collected. Results: Results from the visual search task show that groups with ADHD symptoms (ADHD and ASD+) have increased intra-subject variability, whereas only the ASD- group showed signs of superior performance. Fixation durations during the copying down task can differentiate ASD- and ADHD groups on the strategies used. The gaze cueing task, shows the ASD+ group to use different strategies as compared to TD, and have slower and more variable saccadic RTs as compared to ADHD and ASD-. Conclusion: The present study gives evidence for a double dissociation between ADHD and ASD when no comorbid symptoms are present, on paradigms of local-global processing and social cueing. Oculomotor paradigms and analysis have successfully teased apart this interaction in the present study and can aid greatly in the quest for these endophenotypes. [ABSTRACT FROM AUTHOR]