The role of the temporal lobes in recognizing visuospatial materials: remembering versus knowing.

Recognition memory for abstract visuospatial designs was assessed in unilateral temporal lobe epilepsy (TLE) patients and normal controls using a remember/know recognition paradigm. Subjects assigned "remember" judgments to recognized items for which they could recall the study presentation, and "know" judgments to items recognized on the basis of familiarity without conscious recollection of the study episode. In Experiment 1 normal controls and left TLE patients gave more "know" than "remember" recognition judgments for visuospatial materials. Right TLE subjects, however, showed the opposite response pattern. Experiment 1a demonstrated that this dissociation between left and right temporal patients occurred in both presurgery and postsurgery patients. In Experiment 2 recognition was assessed following encoding conditions in which subjects answered questions about either the number of lines in the designs or the appropriateness of verbal labels for presented stimuli. The previous pattern of "know" and "remember" responses was replicated for all groups in the line count condition, but was reversed for normal controls in the label condition. These results are interpreted within a theoretical framework in which "remember" responses are based on the contribution of distinctiveness of individual items to recognition whereas "know" judgements reflect perceptual fluency.