Conditional Discrimination Learning in Patients With Bilateral Medial Temporal Lobe Amnesia.

The ability of bilateral medial temporal lobe amnesic patients (MT; n=8) and normal participants (NC; n=8) to acquire a conditional discrimination in trace and delay eyeblink conditioning paradigms was investigated. Experiment 1 assessed trace conditional discrimination learning by using a light conditional stimulus (S+/S-) and tone conditioned stimulus (CS) separated by a 1-s trace. NCs responded differentially on S+ trials (mean percent conditioned responses=66) versus S- trials (30). Whereas MTs were impaired in their acquisition of the conditional discrimination (S+=51, S-=43). In Experiment 2, the temporal separation was eliminated. NCs acquired the conditional discrimination (S+=70, S-=29). MTs were unable to respond differentially (S+=42, S-=37). The findings indicate that the hippocampal system is essential in acquiring a conditional discrimination, even in a delay paradigm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)