ALTERATIONS OF SIZE CONSTANCY ASSOCIATED WITH BRAIN LESIONS IN MAN

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Abstract
To show the association of central nervous mechanisms with the primary afferent projections of the retina, size constancy judgements were measured in 39 patients, each having a single brain lesion, and in 36 control subjects. Results indicate that in cases both of monocular and binocular vision size constancy is significantly disturbed only when the lesion is in the parietal cortex of either hemisphere. These disturbances are due to a perceptual disorder at a central level because they are independent of any defects in the visual field. The deviation in the measurements was in the direction of over-constancy. Theoretical interpretations suggest that lesions in the parietal cortex may alter size constancy judgements because afferent discharges from ocular muscle receptors can no longer be coordinated with impulses from the primary retinal afferent systems.