关键词: 空间工作记忆, 海马, 位置细胞, 位置野, 多通道记录

Abstract: Hippocampus plays a vital role in the formation of spatial working memory. The brain encodes spatial information by generating spatial cognitive map in hippocampus. The mechanism with which hippocampus encodes, integrates, and extracts information remains unclear. According to Hebb’s cell assembly hypothesis, spatial information is distributed in neural network. In this study, the dynamic processing of neuronal information in hippocampus CA1 neurons was observed in behaving adult rats and the neuronal mechanisms of spatial working memory were analyzed.
A 16-channel (2×8) multi-electrode array was surgically imbedded into hippocampus CA1 area under general anesthetization. After the animals recovered from the surgery, they were trained in T-maze for delay-alternation task. 13 training trials (inter-trials interval 20 sec) were performed each day for about 7-14 days. The multi-electrode array was cable-connected to a multi-channel acquisition system for simultaneous recording and displaying of neuronal units discharges and local field potentials. While the neuronal signals and animal spatial positions were recorded, the event marker was inputted in synchrony.
Relationships between the events and neuronal unit discharges or local field potentials were analyzed during spatial memory formation. It was found that hippocampus CA1 neurons exhibited discharges correlating to door-opening and turning. Based on the correlating events, CA1 neurons can be classified into door-opening neurons, turning neurons, and double-place field neurons. When the animals were in the stem of the T-maze, hippocampus neurons showed context-dependent differential discharging. Some neurons showed discharges that predicted goal-directed behavior. The place fields of place neurons were gradually formed during learning and memory, but they were not stable until the formation of memory. The correlations between neurons also became stronger during memory formation. The same or different theta oscillation (4-12Hz) was observed between neuronal discharges or between neuronal discharge and local field potential. Besides, the theta oscillation exhibited event-correlation: it appeared before door-opening or turning.
The results suggest that neurons in CA1 area of hippocampus are involved in the primary processing of spatial information to guide the prospective search behavior. In the formation of spatial memory, hippocampus neuronal assembly process information not only through spatial encoding, but also through temporal encoding.

Key words: spatial working memory, hippocampus, place cell, place field, muti-channel recording