Distractibility after unilateral resections from the frontal and anterior cingulate cortex in humans

The prefrontal and anterior cingulate cortex figure prominently in current models of directed attention. The efficacy of selective attention was studied in a distractibility study carried out with patients who had unilateral surgical excisions from the frontal cortex with or without involvement of the cingulate gyrus, patients with unilateral anterior temporal resections, and normal control subjects. In Task A, participants responded to target stimuli presented at the foveal location in the presence or absence of distracting peripheral stimuli that appeared 200 ms before the target's onset. The presence of a distractor caused a comparable increase in reaction times to targets across all groups. In Task B, a distractor appeared during every trial but it appeared at a new location on 12% of the trials. A comparable transient increase in reaction times was observed in patients with frontal cortical resections that spared the anterior cingulate gyrus, patients with anterior temporal lobe resections, and the normal control group. Thus, lesions restricted to the prefrontal cortex need not impair the ability to attend and respond to a target event in the presence of distraction. Interestingly, no distracting effect was observed during Task B in patients with lesions that invaded the anterior cingulate gyrus, suggesting that this cortical region is involved in responding to or habituating to environmental stimuli.