| 研究実績の概要 |
A study was undertaken to determine the functional significance of medial and lateral entorhinal cortex (MEC, LEC) in episodic memory. We optogenetically inhibited neuronal activity in either MEC or LEC while animals were learning a spatial/object recognition task, which previous lesion/pharmacological studies hinted to be processed by MEC/LEC, respectively. A strong point to our study was the fact that we inhibited neuronal activity specifically during the acquisition period, which was not the case with the lesion/pharmacological manipulations. We also developed a unique behavioral test - fear conditioning to a place or object - to tease out differential functions of the two entorhinal cortex subregions. We found that indeed inhibiting LEC during acquisition suppressed memory of object. Following MEC inhibition, animal's memory for place was inhibited, however, the LEC inhibited animals also showed a fear for place, although not to the same extent.
A second objective was to determine how inputs from MEC/LEC may play a role in neuronal organization in the hippocampus. We had previously shown that the hippocampus is organized in cell clusters to encode all types of memories - spatial, fear, sequential. However, the driving input for cluster formation is totally unknown. To solve this question, we have investigated the effects of optogenetic activation of each input arising from the MEC/LEC on cellular activation patterns in the hippocampus using the activity dependent IEG Zif268. Data indicate that these inputs may indeed provide the input for cluster formation.
|
