Saturday, July 24, 2010

Go, no go task, parcellated and localized within the VLPFC and pre SMA

Chikazoe J.  Localizing performance of go/no-go tasks to prefrontal cortical subregions.  Curr Opin Psych 2010; 23: 267-272. 

Author divides go/no go tasks into components including working memory, stimulus-driven attention ( reorienting of attention), error monitoring, top down control processes, and response inhibition.  The literature suggests the VLPFC is key to response inhibition (see Buxbaum et al, Hum Brain Mapping 2005).  However, DLPFC and pre-SMA also are recruited for this task and for stop-signal and for antisaccade tasks.

Transcranial magnetic stimulation of right VLPFC disrupts response inhibition, but stimulation of left IFG, DLPFC, dorsal premotor cortex, and right angular gyrus does not.  Subregions of the VLPFC play different roles.  The subregions are posterior IFG, inferior frontal junction, and IFG/insula. 

pIFG usually activates with go/no go stimuli.  IFJ, located at border of inferior frontal sulcus and precentral sulcus, is associated with processing infrequent stimuli.  Thus pIFG is the "core region" for go/no go response inhibition. The same area is involved in reorienting attention (see Corbetta M, Neuron 2008).  The reorienting attention network involves pIFG, IFJ, IFG/insula, and temporal parietal junction.  This is segregated from a dorsal network involving the frontal eye fields (FEF), and intraparietal sulcus that employs a top down mechanism . pIFG may activate with both networks and provide the communication between the two. 

IFJ is involved in stimulus driven attention and is more involved in processing infrequent stimuli, such as infrequent go or infrequent no go on go/no go tasks.  By contrast pIFG is only activated on infrequent no go. 

IFG insula is activated, but is tough to differentiate from insula and IFG insula is also activated in many other tasks.  Its function is not specific and it may be more related to task awareness. 

Pre SMA on right is also core to response inhibition.  This is true on both lesion studies and TMR studies.  Pre SMA is robustly activated during go/no go whether the task is simple or complex or whether the test is oral or manual.  Pre SMA is thought to be important to conflict resolution of task.  The anteriror cingulate gyrus (ACC) activates for error processing.  DLPFC activation may be related to top down processes and working memory. 

Hemispheric asymmetry with right sided dominance is noted in most studies especially for pIFG.  However the left pre SMA and VLPFC may be important.  "Balance" may be disrupted with left sided lesions that can thus cause deficits on task also. 

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