FUNCTIONAL LOCALIZATION OF THE SYSTEM FOR VISUOSPATIAL ATTENTION USING POSITRON EMISSION TOMOGRAPHY

PET was used to image the neural system underlying visuospatial attent ion. Analysis of data at both the group and individual-subject level p rovided anatomical resolution superior to that described to date. Six right-handed male subjects were selected from a pilot behavioural stud y in which behavioural responses and eye movements were recorded. The attention tasks involved covert shifts of attention, where peripheral cues indicated the location of subsequent target stimuli to be discrim inated. One attention condition emphasized reflexive aspects of spatia l orientation, while the other required controlled shifts of attention . PET activations agreed closely with the cortical regions recently pr oposed to form the core of a neural network for spatial attention. The two attention tasks evoked largely overlapping patterns of neural act ivation, supporting the existence of a general neural system for visuo spatial attention with regional functional specialization. Specificall y, neocortical activations were observed in the right anterior cingula te gyrus (Brodmann area 24), in the intraparietal sulcus of right post erior parietal cortex, and in the mesial and lateral premotor cortices (Brodmann area 6).