PATTERNS OF OCULOMOTOR SCANNING IN PATIENTS WITH UNILATERAL POSTERIORPARIETAL OR FRONTAL-LOBE DAMAGE

Eye movements were recorded during the inspection of dot patterns in c ontrol subjects and in patients with acquired unilateral brain damage involving posterior parietal or frontal cortical regions. Normal subje cts adapted their oculomotor scanning pattern effectively to the stimu lus configuration. Patients' oculomotor scanning patterns were charact erized by a rather rigid sequence of fixations and saccades, with no e vidence for a systematic and flexible spatio-temporal organization. In a stimulus condition where dots were grouped, patients with frontal d amage accurately shifted their gaze between the dot groups, but had di fficulties with dot sampling. These observations suggest that the post erior parietal damage mainly affected the visuo-spatial guidance of th e scanpath, whereas the frontal damage impaired its planning. It is co ncluded that both, posterior parietal and frontal brain structures, an d their reciprocal connections, are part of a distributed neural netwo rk subserving visually-guided oculomotor scanning, and that the spatio temporal organization of the scanpath depends critically on both struc tures and their close co-operation. (C) 1997 Elsevier Science Ltd.