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Inhibitory control of memory retrieval and motor processing associated with the right lateral prefrontal cortex: evidence from deficits in individuals with ADHD.

ABSTRACT: Studies of inhibitory control have focused on inhibition of motor responses. Individuals with ADHD consistently show reductions in inhibitory control and exhibit reduced activity of rLPFC activity compared to controls when performing such tasks. Recently these same brain regions have been implicated in the inhibition of memory retrieval. The degree to which inhibition of motor responses and inhibition of memory retrieval might involve overlapping systems has been relatively unexplored. The current study examined whether inhibitory difficulties in ADHD extend to inhibitory control over memory retrieval. During fMRI 16 individuals with ADHD and 16 controls performed the Think/No-Think (TNT) task. Behaviorally, the Stop Signal Reaction Time task (SSRT) was used to assess inhibitory control over motor responses. To link both of these measures to behavior, the severity of inattentive and hyperactive symptomatology was also assessed. Behaviorally, ADHD individuals had specific difficulty in inhibiting, but not in elaborating/increasing memory retrieval, which was correlated with symptom severity and longer SSRT. Additionally, ADHD individuals showed reduced activity in rLPFC during the TNT, as compared to control individuals. Moreover, unlike controls, in whom the correlation between activity of the rMFG and hippocampus predicts inhibitory success, no such correlation was observed for ADHD individuals. Moreover, decreased activity in rIFG in individuals with ADHD predicted a decrease in the ability to inhibit motor responses. These results suggest that inhibitory functions of rLPFC include control over both memory and motoric processes. They also suggest that inhibitory deficits in individuals with ADHD extend to the memory domain.

SUBMITTER: Depue BE

PROVIDER: S-EPMC2979319 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Inhibitory control of memory retrieval and motor processing associated with the right lateral prefrontal cortex: evidence from deficits in individuals with ADHD.

Depue B E BE Burgess G C GC Willcutt E G EG Ruzic L L Banich M T MT

Neuropsychologia 20100921 13

Studies of inhibitory control have focused on inhibition of motor responses. Individuals with ADHD consistently show reductions in inhibitory control and exhibit reduced activity of rLPFC activity compared to controls when performing such tasks. Recently these same brain regions have been implicated in the inhibition of memory retrieval. The degree to which inhibition of motor responses and inhibition of memory retrieval might involve overlapping systems has been relatively unexplored. The curre ...[more]

PMID: 20863843

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Project description:The lateral prefrontal cortex (LPFC) and anterior cingulate cortex (ACC) of the primate play distinctive roles in the mediation of complex cognitive tasks. Compared with the LPFC, integration of information by the ACC can span longer timescales and requires stronger engagement of inhibitory processes. Here, we reveal the synaptic mechanism likely to underlie these differences using in vitro patch-clamp recordings of synaptic events and multiscale imaging of synaptic markers in rhesus monkeys. Although excitatory synaptic signaling does not differ, the level of synaptic inhibition is much higher in ACC than LPFC layer 3 pyramidal neurons, with a significantly higher frequency (∼6×) and longer duration of inhibitory synaptic currents. The number of inhibitory synapses and the ratio of cholecystokinin to parvalbumin-positive inhibitory inputs are also significantly higher in ACC compared with LPFC neurons. Therefore, inhibition is functionally and structurally more robust and diverse in ACC than in LPFC, resulting in a lower excitatory: inhibitory ratio and a greater dynamic range for signal integration and network oscillation by the ACC. These differences in inhibitory circuitry likely underlie the distinctive network dynamics in ACC and LPC during normal and pathological brain states.SIGNIFICANCE STATEMENT The lateral prefrontal cortex (LPFC) and anterior cingulate cortex (ACC) play temporally distinct roles during the execution of cognitive tasks (rapid working memory during ongoing tasks and long-term memory to guide future action, respectively). Compared with LPFC-mediated tasks, ACC-mediated tasks can span longer timescales and require stronger engagement of inhibition. This study shows that inhibitory signaling is much more robust and diverse in the ACC than in the LPFC. Therefore, there is a lower excitatory: inhibitory synaptic ratio and a greater dynamic range for signal integration and oscillatory behavior in the ACC. These significant differences in inhibitory synaptic transmission form an important basis for the differential timing of cognitive processing by the LPFC and ACC in normal and pathological brain states.

Dataset Information

Inhibitory control of memory retrieval and motor processing associated with the right lateral prefrontal cortex: evidence from deficits in individuals with ADHD.

Publications

Inhibitory control of memory retrieval and motor processing associated with the right lateral prefrontal cortex: evidence from deficits in individuals with ADHD.

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