Memories are made of this: the effects of time on stored visual knowledge in a case of visual agnosia

We report the effects of the passage of time on the longterm visual knowled ge for objects in a patient with visual agnosia (H.J.A.). The naming of rea l objects was found to have improved, although this was not associated with any change in H,J,A,'s basic perceptual abilities which were stable ever a 16-year period, The improvement in object naming was attributed to better use of non-contour-based visual information (such as surface detail and dep th cues). In addition, we demonstrate a deterioration in H.J.A.'s long-term memory for the visual properties of objects, and argue that this has occur red as a result of his having impaired perceptual input, The deterioration was only apparent in drawing from memory and in the verbal descriptions of items; with forced-choice testing, H.J.A. operated at ceiling; we propose t hat current tests of visual imagery may not be sufficiently sensitive to de tect subtle impairments of visual memory, Our findings can be taken to indi cate that perceptual and memorial processes are not functionally independen t, but are linked in an interactive manner.