The effect of stroke on object recognition.

Stroke patients were tested for their ability to recognize familiar objects shown in photographs, and we have confirmed previous reports that damage to the right hemisphere impairs recognition of objects shown at an "unusual angle". Additionally, these patients were impaired in matching unfamiliar (nonsense) objects which had been rotated. These impairments are discussed in the context of key task demands, particularly the need to extract depth cues from the photographs, and to rotate form elements to determine whether the samples provided different views of the same object. In the context of other work, these results suggest impairment of advanced perceptual skills which are needed to establish relationships of and among features of the forms.