Effects of prior exposure on music liking and recognition in patients with temporal lobe lesions

Prior exposure to music typically increases liking. This manifestation of implicit memory can be dissociated from explicit memory recognition. To examine the contribution of the medial temporal lobe to musical preference and recognition, we tested patients with either left (LTL) or right (RTL) temporal lobe lesions as well as normal control (NC) participants using the procedure of Peretz et al. The results in the affect task showed that NC and LTL participants preferred the studied over nonstudied melodies, thereby demonstrating an implicit exposure effect on liking judgments, whereas RTL patients failed to exhibit this effect. Explicit recognition was impaired in both LTL and RTL patients as compared to NC participants. On the basis of these findings, we suggest that RTL structures play a critical role in the formation of melody representations that support both priming and memory recognition, whereas LTL structures are more involved in the explicit retrieval of melodies. Furthermore, we were able to test an amnesic patient (PC) with bilateral lesions of the temporal lobe. In this case, the exposure effect on liking was also absent. However, repeated exposure to melodies was found to enhance both liking and recognition judgments. This remarkable sparing of memory observed through melody repetition suggests that extensive exposure may assist both implicit and explicit memory in the presence of global amnesia.