Left hemisphere strategies in visual recognition, topographical orientation and time planning.

Right hemisphere lesions are known to impair, in many cases, visual recognition and visuospatial orientation. We report here on the compensatory strategies used by a patient whose posterior part of the right hemisphere was either destroyed or visually deafferented. She presented a slight appreceptive agnosia, memory disorders, and severe topographical disorientation. Her strategy relied on detail-by-detail analysis of buildings for recognition and on identification of landmarks and memorization of their sequences for finding routes. Time planning was impaired; the patient was unable to use a bi-dimensional timetable, but relied on a (linear) list of assignments. The linear, speech-related strategy she used was sustained uniquely by left hemisphere networks, since no processing of visual information occurred in the right hemisphere.