Material-specific deficits in "remembering" in patients with unilateral temporal lobe epilepsy and excisions

A growing body of research suggests that "remembering" and "knowing" may be dissociable aspects of recognition memory. Cognitive theorists have argued that the former reflects conceptual processing and is based on distinctive memory traces whereas the latter is associated with perceptual analysis and reflects fluency of processing. Here, we investigate whether this framework can account for memory deficits observed following right or left temporal lobe damage, as suggested by Blaxton and Theodore [Brain and Cognition 35 (1997) 5]. Recognition memory for faces and words was examined in patients with unilateral temporal lobe epilepsy or excisions (TLE) and controls using the "remember-know" recognition paradigm. Participants studied items under conditions designed to enhance either conceptual processing or focus their attention on superficial aspects of the items. For controls, there was an increase in "remember" responses following conceptually-based encoding for both words and faces. This enhancement was eliminated in patients with left TLE for words and those with right TLE showed a diminished effect for faces. This pattern indicates an impairment in the ability to benefit from conceptual encoding that is specific to material preferentially processed by the damaged hemisphere. Furthermore, this effect was only observed for "remember" responses, which are based on the participants' ability to recollect specific contextual aspects of the original study experience. These data can be interpreted in relation to current theories of hippocampal function, which emphasize the critical role played by the hippocampus in relational memory formation and retrieval. We offer this as a novel interpretation of the "remember-know" literature.