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    ABSTRACT: Survival can depend on the ability to change a current course of action to respond to potentially advantageous or threatening stimuli. This "reorienting" response involves the coordinated action of a right hemisphere dominant ventral frontoparietal network that interrupts and resets ongoing activity and a dorsal frontoparietal network specialized for selecting and linking stimuli and responses. At rest, each network is distinct and internally correlated, but when attention is focused, the ventral network is suppressed to prevent reorienting to distracting events. These different patterns of recruitment may reflect inputs to the ventral attention network from the locus coeruleus/norepinephrine system. While originally conceptualized as a system for redirecting attention from one object to another, recent evidence suggests a more general role in switching between networks, which may explain recent evidence of its involvement in functions such as social cognition.
    Neuron 06/2008; 58(3):306-24. · 15.77 Impact Factor
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    ABSTRACT: Earlier studies have suggested an impairment in the attention and eye movement control of children with ADHD. An important phenomenon in the control of attentional shifts and eye movements is the inhibition of return (IOR), which states that our brain works in a way that prevents our attention from returning to a spatial location that has been attended to, either overtly or covertly. This current study addresses whether the IOR in oculomotor planning is compromised in children with ADHD. Eleven ADHD and 12 age- and gender-matched control subjects participated in a behavioral task, in which they made saccades to a peripheral target after a valid, invalid or neutral cue. The latency difference between cued and uncued saccades over a range of cue-target onset asynchrony as well as the positive component of this latency profile (i.e., IOR) was compared between groups. The results show that ADHD children demonstrate a biphasic latency profile that is grossly similar to that observed in control subjects, although the magnitude of IOR appears to be slightly smaller in ADHD subjects. These preliminary results suggest that the inhibitory attention mechanism subserving IOR is at least not fully compromised in ADHD children.
    Experimental Brain Research 04/2003; 149(1):125-30. · 2.22 Impact Factor
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    ABSTRACT: Heightened distractibility in participants with ADHD as indexed by increased reaction time (RT) variability has been hypothesized to be due to a failure to sufficiently suppress activation in the default attention network during cognitively demanding situations. The present study utilized fMRI to examine the relationship between intra-individual variability (IIV) in task RT and suppression of BOLD response in regions of the default network, using a working memory paradigm and two levels of control tasks. IIV was calculated separately for thirteen healthy control and twelve children with ADHD, Combined Type. Children with ADHD displayed significantly more RT variability than controls. Neural measures showed that although both groups displayed a pattern of increasing deactivation of the medial prefrontal cortex (PFC) with increasing task difficulty, the ADHD group was significantly less deactive than controls. Correlations between IIV and brain activation suggested that greater variability was associated with a failure to deactivate ventromedial PFC with increasing task difficulty. T-tests on brain activation between participants with ADHD with low versus high IIV implicated a similar region so that high variability was associated with greater activity in this region. These data provide support for the theory that increased distractibility in at least some participants with ADHD may be due to an inability to sufficiently suppress activity in the default attention network in response to increasing task difficulty.
    Brain research 04/2009; 1273:114-28. · 2.46 Impact Factor

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