Roles of the Medial Geniculate Nucleus in Potentiated-Startle Response

Kim, Jae-Il; 김재일; Kim, Hyun-Taek; 김현택; Kim, Ki-Suk; 김기석

Abstract

In many previous studies, it has been reported that lesions of the medial geniculate nucleus (MGN) which is the part of acoustic thalmaus blocked conditioned emotional response, such as differential bradycardiac response, blood pressure, and freezing response. So, it has been suggested that MGN is a neural structure that is involved in conditioned emotional responses. But, considering MUA and LTP are developed in MGN during conditioning and MGN receives convergent acoustic CS and electrical US input, it may be regarded that MGN is a structure of plasticity, not simply a neural structure. The purpose of this was to indentify the roles of MGN whin the neural circuit involved in fear when it used fear-potentiated startle response as a measure of fear. In experiment 1, after the conditioning that paired acoustc CS with electrical shock US, electrolytic bilateral lesions were administered to the MGN. Results were that the unoperated group and the sham surgery group showed fear-potentiated startle response, but on the other hand the lesioned group did not. In experiment 2, AP-5, which blocks LTP as a NMDA receptor antagonist, was microinjected to MGN before conditioning trials and test trial. Results revealed that the animals which AP-5 was microinjected before conditioning trials did not show potentiated startle response, but the animal which AP-5 was microinjected before test trial did. These observations consist with previous reports that NMDA receptor antagonist blocked acquisition not performance of learning. So it can be concluded that these findings indicate MGN is a structure of neural plasticity as well as a neural structure in emotion conditioning using acoustic CS and electrical shock US.

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Article Contents

Vol.4

Roles of the Medial Geniculate Nucleus in Potentiated-Startle Response

Abstract

The Korean Journal of Cognitive and Biological Psychology