| Summary: | 碩士 === 國立臺灣大學 === 心理學研究所 === 103 === This study aims to understand the neural mechanisms underlying storage of fear memory and its update over time. The neural mechanism subserving consolidation of fear memory has been well documented, but little is known for storage maintenance of it. Previous evidence showed that inhibition of protein kinase M zeta (PKMz), which is proposed to support cellular changes for memory storage within the amygdala, dorsal hippocampus (DH) or medial prefrontal cortex (mPFC), impaired tasks involving fear, space or drug related information respectively. The inhibitory avoidance (IA) task and contextual fear conditioning (CFC) task are two different types of fear learning that respectively engaged instrumental or classical conditioning. However, the role of PKMz within these three areas in memory storage of the IA and CFC tasks remains unknown. To address this question, male Wistar rats with cannulae implanted in one of these areas were trained on either one-trial step-through IA task or two-phase training paradigm of CFC task. They were randomly assigned to receive a PKMz inhibitor - ZIP (10 nmole/ul) or vehicle infusion in different time points. The results showed that for IA task, intra-amygdala, -DH, or -mPFC infusion of ZIP one day after training impaired fear memory. For treatments in the amygdala and DH, the effect was apparent in the recent memory tests, but that in the mPFC was not apparent until the remote memory test. On the other hand, for the CFC task infusion of ZIP into the amygdala impaired recent memory, however, there was no such effect on memory when intra-mPFC infusion of ZIP. These findings suggest that fear memory would store in different brain regions according to different types of learning tasks. Further, PKMz may have different roles in different kinds of memory processes.
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