Neuronal connection changes related to auditory working and reference memory in the rat.

点击翻译按钮获取中文摘要

This research project experimentally investigates connection changes in small neuronal circuits, cell assemblies, in relation to information processing of higher memory. The subjects were albino rats. The to-be-remembered stimuli were high and low tones. A method was defined to test working and reference memory alternatively in a short period in which units could be recorded continuously. The apparatus and stimuli were identical for both the working and reference memory tasks. Several units were recorded simultaneously from the hippocampal or auditory regions during the performance of both of the tasks. Frequency histograms revealed that units showed task-related activities in the reference memory task or working memory task or both of the tasks. The reference memory task had more task-related units than the working memory task had. Cross-correlation analysis was conducted for each pair of simultaneously recorded units to see synaptic connectivity diagrams of the units. To the present, the analysis has shown a few units which changed their synaptic connections between the tone-presented and the retention periods or between the working and reference memory tasks. There were more common excitatory or inhibitory inputs than mutual direct synaptic connections. These preliminary results indicate the followings : 1. A neuron could have different functions between the different memory processes. 2. Synaptic connections in a small neuronal circuit could show dynamic changes between the different processes in a memory task or between the different memory tasks. The followings should be investigated in the near future : 1. Relationship of functions of individual neurons and possibility of their synaptic changes. 2. Changes of contribution of synaptic changes. 3. Differences between the sensory and hippocampal regions.