CELL-ASSEMBLY CODING IN SEVERAL MEMORY PRECESSES

The present paper discusses why the cell assembly, i.e., an ensemble p opulation of neurons with flexible functional connections, is a tenabl e view of the basic code for information processes in the brain. The m ain properties indicating the reality of cell-assembly coding are neur ons overlaps among different assemblies and connection dynamics within and among the assemblies. The former can be detected as multiple func tions of individual neurons in processing different kinds of informati on, individual neurons appear to be involved in multiple information p rocesses. The latter can be detected as changes of functional synaptic connections in processing different kinds of information. Correlation s of activity among some of the recorded neurons appear to change in m ultiple information processes. Recent experiments have compared severa l different memory processes (tasks) and detected these two main prope rties, indicating cell-assembly coding of memory in the working brain. The first experiment compared different types of processing of identi cal stimuli, i.e., working memory and reference memory of auditory sti muli. The second experiment compared identical processes of different types of stimuli, i.e., discriminations of simple auditory, simple vis ual, and configural auditory-visual stimuli. The third experiment comp ared identical processes of different types of stimuli with or without temporal processing of stimuli, i.e., discriminations of elemental au ditory, configural auditory-visual, and sequential auditory-visual sti muli. Some possible features of the cell-assembly coding, especially ' 'dual coding'' by individual neurons and cell assemblies, are discusse d for future experimental approaches. (C) 1998 Academic Press.