Stereopsis and magnocellular sensitivity in schizophrenia.

There is evidence to indicate that schizophrenic individuals, in addition to cognitive deficiencies, also suffer from visual deficits. These deficits, it has been proposed, are the result of a deficiency in the magnocellular portion of the early visual system. A number of approaches have been used in attempts to assess the sensitivity of the magnocellular system in individuals with schizophrenia. It has recently been proposed that magnocellular sensitivity can be tested by measuring stereo acuity, i.e. by measuring the accuracy with which visual depth can be detected based on differences in the retinal images in the two eyes. This suggestion was based on early claims which linked stereopsis, i.e. the visual perception of depth generated from differences in the two retinal images, to the magnocellular system. We here review more recent results which indicate that stereopsis and stereo acuity are more closely linked to the parvocellular system. It is concluded that stereo acuity is not an appropriate test for assessing magnocellular sensitivity. The present considerations undermine the claim that magnocellular deficits are linked to schizophrenia.