Visual evoked responses in lesions of the higher optic pathways

Abstract

Effects of higher visual pathway lesions upon visual evoked responses have been described, the findings in 29 patients with visual field loss being contrasted with those of 80 normal individuals and 19 patients with brain lesions not affecting vision. While the observed distortions were complex and variable, no patient of 23 with hemianopic homonymous field defect had a normally symmetrical response. Of 6 patients with quadrantic field defect, 2 had symmetrical responses, both having superior quadrantanopsias. Patients with macular involvement could not be differentiated from those without. Slow rise times with later culminations of waves OI and OH, surface-negative and -positive, respectively, opposite the affected homonymous foeld, were most characteristic of visual pathway damage. Suppression of OV, also contralateral to the affected field, correlated both with visual system damage and suppression of the resting alpha rhythm. Reconstitution of the normal features of the visual evoked response accompanied recovery from a visual field defect. It was concluded that, in man, electrophysiologic activity of the occipital region extending over approximately 100 msec. after stimulation is associated with basic visual perceptual processes.