OBJECT RECOGNITION DIFFICULTY IN VISUAL APPERCEPTIVE AGNOSIA

Two patients with visual apperceptive agnosia were examined on tasks a ssessing the appreciation of visual material. Elementary visual functi oning was relatively preserved, but they had profound difficulty recog nizing and naming line drawings. More detailed evaluation revealed acc urate recognition of regular geometric shapes and colors, but performa nce deteriorated when the shapes were made more complex visually, when multiple-choice arrays contained larger numbers of simple targets and foils, and when a mental manipulation such as a rotation was required . The recognition of letters and words was similarly compromised. Nami ng, recognition, and anomaly judgments of colored pictures and real ob jects were more accurate than similar decisions involving black-and-wh ite line drawings. Visual imagery for shapes, letters, and objects app eared to be more accurate than visual perception of the same materials . We hypothesize that object recognition difficulty in visual appercep tive agnosia is due to two related factors: the impaired appreciation of the visual perceptual features that constitute objects, and a limit ation in the cognitive resources that are available for processing dem anding material within the visual modality. (C) 1997 Academic Press.