Spared Discrimination and Impaired Reversal Eyeblink Conditioning in Patients with Temporal Lobe Amnesia

Abstract

The effect of medial temporal lobe damage on a two tone delay discrimination and reversal paradigm was examined in human classical eyeblink conditioning. Eight medial temporal lobe amnesics and their demographically matched controls were compared. Amnesics were able to distinguish between two tones during the initial discrimination phase of the experiment almost as well as control participants. Amnesic patients were not able to reverse the previously acquired two tone discrimination. In contrast, the control participants showed improved discrimination performance after the reversal of the tones. These findings support the hypothesis that the hippocampus, and associated temporal lobe regions, play a role in eyeblink conditioning that becomes essential in more complex versions of the task, such as the reversal of an acquired two tone discrimination.