PARIETAL DAMAGE AND NARROW SPOTLIGHT SPATIAL ATTENTION

Patients with parietal volume loss showed electrophysiological and beh avioral signs of abnormally narrow regions of enhancement of sensory s timulation at an attended location. On a test of focused spatial atten tion, when compared to normal control subjects and patients without pa rietal abnormality, patients with abnormalities of parietal cortex dem onstrated (1) faster button press RTs to targets, (2) earlier P3b even t-related potential (ERP) latencies to targets, and (3) larger than no rmal P1 ERP attention effects (i.e., greater than normal enhancement o f sensory responses at an attended location). These data are evidence for visual attention distributed as a spotlight at the attentional foc us with little surrounding processing enhancement. This dysfunctional attentional map facilitates simple responses within the attentional be am quite well, but could hinder responses outside the beam. Severely g ated sensory responses outside the immediate attentional focus are lik ely to result in severely delayed responses to information in those lo cations. This would be consistent with the response delays seen in pat ients with parietal damage following an incorrect spatial cue (extinct ion-like pattern), and also with clinical observations of inattention in such patients. The patterns of sensory enhancement seen in these da ta suggest a mechanism that may underlie the impairments in spatial at tention that follow damage to parietal cortex, and help to specify the role of parietal cortex in spatial attention.