|Budget Amount *help
¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1996 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1995 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1994 : ¥1,100,000 (Direct Cost : ¥1,100,000)
The plausible basic code for information processing of memory is the "cell assembly", i.e., overlapped populations of neurons with flexible functional connections within and among the populations. The present series of experiment has investigated two main properties of cell assemblies, that is, the overlapping of neurons and the dynamics of synaptic connections, in processing several different processes of memory.
The first experiment compared different types of memory-process of identical stimuli, that is , Working memory and reference memory. In the tasks for them, the apparatus, stimuli and rats were identical and only the types of process required differed. The second experiment compared identical memory-processes for different types of stimuli, that is, simple auditory, simple visual, and configural auditory-visual stimuli. In the tasks for them, the apparatus, types of process and rats were identical and only the types of stimuli differed. The third experiment compared identical m
emory-processes for different aspects of compound stimuli, that is, elemental auditory, configural auditory-visual, and successive auditory-visual stimuli. The tasks for them employed identical apparatus, types of process, types of stimuli and rats. Only the aspects of stimuli to be processed differed.
Activity of individual neurons of the hippocampal formation (CA1, CA3 and dentate gyrus) were recorded during performance of the tasks. Some proportions of the recorded neurons showed task-related differential activation in one, two or all of the tasks in each experiment. These results indicate some functional overlapping of the neurons in multiple memory-processes. A cross-correlation analysis of activities among the simultaneously recorded neurons showed that some of their functional synaptic connections changed among the tasks in each experiment. This indicates the dynamic changes of synaptic connections in different memory-processes. These findings together support the cell-assembly coding of memory processes. Less