PRESERVED VISUAL-IMAGERY IN VISUAL FORM AGNOSIA

We investigated the ability of a patient (D.F.) with profound visual f orm agnosia to perform a variety of tasks requiring visual imagery. De spite her inability to discriminate between objects and patterns of di fferent shapes, sizes, and orientations, D.F. showed quite normal visu al imagery involving these same 'visual' properties when the images we re drawn from long-term memory. Thus, she was able both to scan mental images in search of particular features and to form new images by com bining several known images. While there is growing evidence that perc eption and imagery share common neural substrates, the fact that D.F. shows intact visual imagery in the face of a massive perceptual defici t in form vision challenges recent suggestions that these two psycholo gical processes share common input pathways in early vision. It is sug gested that regions in the occipitotemporal pathway may be important f or the generation of visual images while regions in the posterior pari etal system might be involved in the manipulation of these images.