Exploring the influence of perceptual and attentional load to unmask a spatially selective attention deficit in children with ADHD and unaffected siblings.

Miss Sarah Pollock (). Exploring the influence of perceptual and attentional load to unmask a spatially selective attention deficit in children with ADHD and unaffected siblings. Professional Doctorate, School of Psychology, The University of Queensland.

       
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Author Miss Sarah Pollock
Thesis Title Exploring the influence of perceptual and attentional load to unmask a spatially selective attention deficit in children with ADHD and unaffected siblings.
School, Centre or Institute School of Psychology
Institution The University of Queensland
Thesis type Professional Doctorate
Supervisor A/Prof Mark Bellgrove
Total pages 144
Abstract/Summary Attention Deficit Hyperactivity Disorder (ADHD) is a disorder of childhood affecting up to 6% of children. Increased distractibility and difficulty sustaining attention are diagnostic for ADHD, yet an objective attention deficit has been hard to isolate. An intriguing aspect of the attention deficit of children with ADHD is a subtle inattention to left space, which resembles that seen in right-hemisphere patients with the ‘neglect’ syndrome. This thesis further explores this phenomenon in ADHD using tasks that have been validated on neglect patients. It has been observed in neglect patients that awareness of left hemi-field stimuli is poorer under a cognitive load. What is currently not known is whether this phenomenon of left-neglect in ADHD also runs in families. Since siblings share 50% of their genes in common, one way to approach this problem is to compare ADHD probands with unaffected siblings and non-ADHD controls. If left-neglect in ADHD has its basis in genetics, then a sub-threshold form of this phenomenon might also be present in related but unaffected individuals, compared to controls. Study1- In the current study 11 children ADHD, 10 non-affected siblings and 14 controls performed a variant of the standard flanker task, in which perceptual load (low-load and high-load), congruency (congruent, incongruent) and position of targets (centre, left and right) were varied independently. Specifically, participants were asked to respond to the target presented along a central horizontal row and ignore any flankers that appeared above or below the target. In the low load condition, the target appeared by itself in the centre, left or right position. In the high load condition, the target appeared among five non-target, uppercase letters (S,K,V,J,R), which were randomly placed in each of the five remaining locations. In each condition the target and flanker could be congruent (i.e. both x) or incongruent (i.e. target x and flanker z). In support of previous research, control children demonstrated a larger incongruency effect for left targets then children with ADHD under low perceptual load. This effect is consistent with the phenomenon of pseudo-neglect in non-clinical participants, in which there is subtle directing of attention to left space. Although children with ADHD tended to show greater incongruency effects for right targets under low perceptual load than controls it was not significant in this relatively small sample. In a matched samples analysis of controls, ADHD and siblings, ADHD children tended to be slowest overall for left targets followed by centre and then right positions. Siblings had similar reaction times to left and right targets but slowest for middle, whilst there was no difference in response times for controls. Study 2-Previous research in right hemisphere patients has found that when participants are required to monitor a central Rapid Serial Visual Presentation (RSVP) stream for a nominated stimulus, they are slower to detect concurrent peripheral targets in the left, but not right hemi-field. Eleven children with ADHD, 10 siblings and 14 non-clinical children were asked to detect briefly presented peripheral stimuli (left and right locations). The children were concurrently required to monitor a centrally presented RSVP stream for a nominated probe that occurred under three load conditions: no-load, low-load and high-load. In the RSVP task participants were required to make a non-speeded judgment of probe presence vs. absence, whereas they made a speeded response upon detection of peripheral targets. An interaction between group, load and target location was predicted with ADHD children being slower than non-clinical children to detect targets presented in the left hemi-field under the high-load RSVP condition. Although load robustly slowed reaction times to peripheral targets more in ADHD than non-ADHD children, this effect did not differ as a function of peripheral target side. This thesis found mixed support for the notion of impaired spatial selective attention for left events in ADHD and unaffected siblings. Possible reasons for this non-replication of past work are discussed.
Keyword ADHD Children

 
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Created: Tue, 01 Jun 2010, 22:48:59 EST by Miss Sarah Pollock