The contribution of the right inferior frontal cortex to response inhibition has been demonstrated by previous studies of neuropsychology, electrophysiology, and neuroimaging. The inferior frontal cortex is also known to be activated during processing of infrequent stimuli such as stimulus-driven attention. Response inhibition has most often been investigated using the go/no-go task, and the no-go trials are usually given infrequently to enhance prepotent response tendency. Thus, it has not been clarified whether the inferior frontal activation during the go/no-go task is associated with response inhibition or processing of infrequent stimuli. In the present functional magnetic resonance imaging study, we employed not only frequent-go trials but also infrequent-go trials that were presented as infrequently as the no-go trials. The imaging results demonstrated that the posterior inferior frontal gyrus (pIFG) was activated during response inhibition as revealed by the no-go vs. infrequent-go trials, whereas the inferior frontal junction (IFJ) region was activated primarily during processing of infrequent stimuli as revealed by the infrequent-go versus frequent-go trials. These results indicate that the pIFG and IFJ within the inferior frontal cortex are spatially close but are associated with different cognitive control processes in the go/no-go paradigm.

The go/no-go task, which effectively taps the ability to inhibit prepotent response tendency, has consistently activated the lateral prefrontal cortex, particularly the right inferior frontal gyrus (rIFG). On the other hand, rIFG activation has rarely been reported in the antisaccade task, seemingly an oculomotor version of the manual go/no-go task. One possible explanation for the variable IFG activation is the modality difference of the two tasks: The go/no-go task is performed manually, whereas the antisaccade task is performed in the oculomotor modality. Another explanation is that these two tasks have different task structures that require different cognitive processes: The traditional antisaccade task requires (i) configuration of a preparatory set prior to antisaccade execution and (ii) response inhibition at the time of antisaccade execution, whereas the go/no-go task requires heightened response inhibition under a minimal preparatory set. To test these possibilities, the traditional antisaccade task was modified in the present functional magnetic resonance imaging study such that it required heightened response inhibition at the time of antisaccade execution under a minimal preparatory set. Prominent activation related to response inhibition was observed in multiple frontoparietal regions, including the rIFG. Moreover, meta-analyses revealed that the rIFG activation in the present study was observed in the go/no-go tasks but not in the traditional antisaccade task, indicating that the rIFG activation was sensitive to the task structure difference, but not to the response modality difference. These results suggest that the rIFG is part of a network active during response inhibition across different response modalities.

PTU therapy may be related to the appearance of MPO-ANCA, but MPO-ANCA does not appear to be closely related to vasculitis.

No abstract

The prefrontal cortex implements a set-shifting function that includes inhibition of a previously acquired cognitive set. The impairment of the inhibitory function results in perseverative behavior that forms one characteristic feature of frontal lobe dysfunction. Previous neuroimaging studies have revealed inhibitory mechanisms in the inferior prefrontal cortex. The present functional magnetic resonance imaging study devised "dual-match" stimuli in a set-shifting paradigm that allowed us to temporally isolate the inhibitory processes recruited during exposure to a previously acquired set. Transient activation time-locked to the isolated inhibition was revealed in the left middle frontal gyrus near the superior frontal sulcus. In a control experiment conducted after subjects had been informed and made aware of the exposure, however, the superior prefrontal activation disappeared, and prominent activation was revealed in a set of brain regions that included the left posterior inferior frontal sulcus. These double dissociation results indicate inhibitory mechanisms in the superior prefrontal cortex, alternative to the inferior prefrontal ones, that are activated depending on the subjects' strategy for inhibition of cognitive set.