Residual function in cortically blind hemifields

Abstract.— Identification of figures presented in, outside and across hemianopic areas was tested on three brain injured patients by using a tachistoscope technique. It was found that the portion of a stimulus falling in the intact hemifield may facilitate the detection of a contralateral portion in the cortically blind hemifield, otherwise neglected when presented alone. This is in agreement with observations from an afterimage study (Tojussen, 1977), also suggesting that interhemispheric interactions in man are organized with a mirrorsymmetric topography. It is proposed that some previous observations of completion of bilaterally symmetrical patterns across hemianopic areas may be explained in terms of analogous interactions.