Tachistoscopic identification of contour in patients with brain damage.

Abstract

Tachistoscopic thresholds for correct identification of gaps in a circle were determined for a variety of gap sizes and visual field position in patients with homonymous visual defects, other brain-injured patients and in control subjects. Largest increases in threshold were in amblyopic portions of visual fields of patients with homonymous visual defects; there were also increases of threshold in areas of the involved visual field that were perimetrically normal. There were small but significant elevations of threshold in brain-injured patients as compared with controls. Completion effects of various kinds were reported in the hemianopics. "It is concluded that theories which stress a point-for-point projection of afferent impulses from retina to striate cortex are inadequate for explaining the results obtained in the present study." 17 references.