VISUAL-MOTION PERCEPTION AFTER BRAIN-DAMAGE .2. DEFICITS IN FORM-FROM-MOTION PERCEPTION

We investigated form-from-motion perception (FFM perception) in a samp le of 39 patients with acquired brain damage. Pronounced FFM deficits were found in two patients (FM1 and FM2) with biparietal lesions. Both patients were able to identify the relevant figure, when it was not e mbedded in obstructive texture. Moreover, they could localize the figu res in the FFM condition, although they could not reliably identify th em. The two patients had normal motion coherence thresholds. Their per formance in a static figure-ground task did not differ from that of ot her patients. These findings imply that the FFM deficits are not cause d by impairment of basic visual motion or form perception but are the consequence of damage to a parietal brain structure involved in the co mbined analysis of visual motion and form information. The nature and functional role of this brain structure as well as the implications of our results for models of FFM perception are discussed. (C) 1997 Else vier Science Ltd.