Postersession 3
Poster #: 84
Topic: MMN across species
Friday, Sep 11, 2015
1st floor

Learning-induced plasticity of mismatch negativity in rats

Hirokazu Takahashi & Tomoyo Shiramatsu

Research Center for Advanced Science and Technology, the University of Tokyo, Tokyo, Japan

In this study, we investigated how MMN is affected by acoustic saliency and valence of sound in anesthetized rats. Four groups of rats were investigated: (i), naïve control; (ii), exposed group; (iii), aversive conditioned group; (iv), and appetitive conditioned group. A surface microelectrode array was used to epipially map AEP in response to oddball tone sequences with 700-ms inter-tone interval. In the exposed group, a particular tone was passively presented without any outcome. In the conditioned groups, conditioned stimulus (CS) tone was associated with either a foot shock or food reward. In the naïve control, changes from low-frequency standard tones to high-frequency deviant tones elicited larger MMN than those from high- to low-frequency tones. This result implies that MMN is affected by a spectrum in nature, where low frequency power is usually dominating. In the exposed group, we found that MMN to an exposed tone became smaller than in the naïve control, verifying that sounds with low appearance probability enhance MMN. In addition, both in the aversive and appetitive conditioned groups, MMN to CS tone became larger than in the exposed group, suggesting that MMN represent emotional saliency. Yet, because no difference was found between the aversive and appetitive groups, MMN might not encode emotional valence. Taking together, these results suggest that MMN represents acoustic saliency determined by both infrequency of sounds and saliency of outcomes.