Cognitive and Anatomical Locus of Lesion in a Patient with a Category-specific Semantic Impairment for Living Beings

Abstract

The goal of this study was two fold and consisted of:(a) reassessing the extent and the nature of the cognitive defect shown by a post-encephalitic patient (LA) previously reported as showing a category-specific impairment for living beings; (b) obtaining a more precise picture of the underlying anatomical lesions. The experimental study of the cognitive disorders of LA has given the follow ing results: 1. Her category-specific semantic impairment for living beings still persisted even when the influence of confounding factors (such as word frequency or stimulus familiarity) was controlled. Her performance, however, was disproportionately influenced by familiarity factors. 2. The pattern of impaired and spared semantic categories was very similar to that observed by other authors and taken as proof that the “living/nonliving” dichotomy suffers from important, systematic exceptions. Within the “living” categories, “body parts” were selectively spared, whereas within the “nonliving” categories “food” and “musical instruments” were severely impaired. 3. Both on a naming-by-definition task and on a sentence verification task, in which the same stimuli were described with reference once to visuoperceptual and once to functional-encyclopaedic information, LA showed a disproportionate deficit in using the visual perceptual attributes of animals and of other living beings for identification. 4. The dissociation between knowledge of living and nonliving beings was not limited to tasks exploring the shape of living stimuli (considered as the core of their structural description) but also extended to other aspects of their visual knowledge, such as their colour. 5. On a sound identification task, LA did not show the usual selective impairment for living beings, since she scored as poorly with anim als' sounds as w ith inanimate objects' sounds. From the anatomical point of view, the bilateral lesions resulting from a previous herpes simplex encephalitis involved both the temporo-limbic structures and the inferior temporal cortex. The possible relationships between the selective cognitive defects and the anatomical locus of lesion of patient LA are briefly discussed.