Modeling attention-deficit/hyperactivity disorder: a critical appraisal of the cognitive-energetic model.

https://psy.fsu.edu/clc/Publications/CLC_Kofler2013.pdf

Reaction time variability in ADHD: A meta-analytic review of 319 studies

Selective visual attention describes the tendency of visual processing to be confined largely to stimuli that are relevant to behavior. It is among the most fundamental of cognitive functions, particularly in humans and other primates for whom vision is the dominant sense. We review recent progress in identifying the neural mechanisms of selective visual attention. We discuss evidence from studies of different varieties of selective attention and examine how these varieties alter the processing of stimuli by neurons within the visual system, current knowledge of their causal basis, and methods for assessing attentional dysfunctions. In addition, we identify some key questions that remain in identifying the neural mechanisms that give rise to the selective processing of visual information.

Neural Mechanisms of Selective Visual Attention

We explored the neuropsychological profile for executive functions of children with attention deficit hyperactivity disorder (ADHD) to assess whether problems associated with the two most cited relevant processes-inhibition and attentional problems-were the core of any executive function difficulty. A battery of executive function tests was administered to 31 children with a clinical diagnosis of ADHD and to 33 normal control participants, all aged between 7 and 12. The executive function battery encompassed a number of tasks, selected because each had multiple measures: a sustained attention reaction time task, a related vigilance task, an adaptation of the Hayling Sentence Completion Test, an adaptation of the Brixton Spatial Rule Attainment Test, a Letter Fluency task, a number Stroop task, and an “n-back” working memory task. The overall pattern of the results fit well with those obtained in previous studies as far as abnormalities of the ADHD group in the domain of inhibitory processes, attentional functions, and executive functions. The children with ADHD, although performing well on baseline tasks, performed more poorly than the controls on all the experimental tasks with one borderline exception: Letter Fluency, where the children with ADHD showed a very different pattern than most adult frontal lobe subgroups. However, there was no specific impairment on measures of inhibitory processes. In addition, strategy generation and use were severely affected in the ADHD group. Particular findings fitted well with disorders of a high-level effort system and of a monitoring system.

Executive function profile of children with attention deficit hyperactivity disorder

The attentional blink reflects the impaired ability to identify the 2nd of 2 targets presented in close succession--a phenomenon that is generally thought to reflect a fundamental cognitive limitation. However, the fundamental nature of this impairment has recently been called into question by the counterintuitive finding that task-irrelevant mental activity improves attentional blink performance (C. N. L. Olivers & S. Nieuwenhuis, 2005). The present study found a reduced attentional blink when participants concurrently performed an additional memory task, viewed pictures of positive affective content, or were instructed to focus less on the task. These findings support the hypothesis that the attentional blink is due to an overinvestment of attentional resources in stimulus processing, a suboptimal processing mode that can be counteracted by manipulations promoting divided attention.

/pdf/the-beneficial-effects-of-additional-task-load-positive-1yqmj8lujy.pdf

The Beneficial Effects of Additional Task Load, Positive Affect, and Instruction on the Attentional Blink.

Background: In order to examine the mechanisms mediating selective attention in Attention Deficit Hyperactivity Disorder (ADHD), this study compared the performance of children diagnosed with ADHD to non-clinical controls on a visual search task in three conditions. Method: In the single feature condition, the target differed from distracters in terms of shape only, whilst in the conjunction baseline, the target was defined by shape and colour relative to distracters. In the preview condition, the conjunction stimuli were segmented over time, so that one set of distracters appeared first, followed 1000 ms later by the second set with the target. Results: Although children with ADHD were slower overall than controls, RTs revealed no difference in search mechanisms between groups; for all children, search was more efficient in the single feature and preview conditions than in the conjunction baseline. However, children with ADHD made more errors, especially in the conjunction and preview conditions. Conclusions: Children with ADHD were not impaired in their mechanisms of visual search relative to controls, but their error patterns implied the adoption of a premature response deadline in the conjunction search condition, and an occasional failure to inhibit old items in the preview condition. Keywords: ADHD, computerised testing, reaction time, selective attention, visual search. Abbreviations: ADHD: Attention Deficit Hyperactivity Disorder; CAPA: Child and Adolescent Psychiatric Assessment; CPT: Continuous Performance Test; CTRS: Conners Teacher Rating Scale; CPRS: Conners Parent Rating Scale; RT: Reaction time; WISC: Weschler Intelligence Scale for Children; WRAT: Wide Range Achievement Test.

Exploring selective attention in ADHD: visual search through space and time.

Background: Previous work on visual selective attention in Attention Deficit Hyperactivity Disorder (ADHD) has utilised spatial search paradigms. This study compared ADHD to control children on a temporal search task using Rapid Serial Visual Presentation (RSVP). In addition, the effects of irrelevant singleton distractors on search performance were examined. Method: In each condition, subjects reported the identity of a red letter ‘probe’ in a sequence of white letters which appeared one after the other at a central fixation point. The temporal position of the probe varied from an initial target, which was distinguished by surrounding asterisks. The target was reported in addition to the probe in condition 2, but not in the baseline condition 1. In a third condition, the initial target was not reported, but one of the asterisks appeared as a colour singleton on some trials. Results: All children displayed an ‘attentional blink’ with probe detection reduced when it appeared at close temporal relations relative to the target. This ‘blink’ reduced over time, and there were no group differences in the recovery of performance, although ADHD children made more errors overall. The ADHD group were also more vulnerable than controls to distraction from irrelevant singletons in condition 3. Conclusion: Although the basic mechanisms of selective attention were not impaired in children with ADHD, these children appeared to require more resources to execute the task and were more vulnerable to distraction by irrelevant singletons, indicating deficits in the maintenance of attentional control. Keywords: Attentional blink, selective attention, visual search, ADHD.

Insights into the control of attentional set in ADHD using the attentional blink paradigm.

We report the data on effects on visual search of (1) preview displays and (2) singleton targets and distractors in IQ-matched ADHD and control children. All children showed interference from singleton distractors even when targets never carried singleton values. This interference from singleton distractors increased under preview conditions, indicating that the children then had fewer resources available to control attention. There was also one selective deficit for ADHD children; they showed marked problems in responding to singleton targets following preview displays. This suggests that, in ADHD, there is either a selective delay or an impairment in switching attentional sets (from a negative set to the preview to a positive set to a singleton target). We discuss the implications for understanding both ADHD and the development of selective attention.

Deanna J. Mason

Papers

Exploring selective attention in ADHD: visual search through space and time.

Insights into the control of attentional set in ADHD using the attentional blink paradigm.

Visual search, singleton capture, and the control of attentional set in ADHD.