We will continue static and dynamic studies of neuronal assemblies by recording simultaneously from as many neurons as the currently developed extracellular technology permits. Such recording methods will be further extended both with multiple fine wire methods, and with optical dye fluorescence methods. Additional mathematical methods for analysis of multiple spike trains and for finding favored firing pattern sequences among several neurons will be examined. These various developments will be brought together in experimental studies of neuronal assemblies during the passage of appropriate sensory information or during behavioral paradigms that force placticity. Preparations to be examined inculde cat auditory cortex and the crayfish claw control system. In each case we will measure the possibly dynamic membership of individual neurons in assemblies as a function of stimulus or behavioral variables. We will seek the organizing principles as well as the anatomical description of assemblies that we detect. As in pilot projects, the cortical work will emphasize intracolumnar versus intercolumnar relationships by using appropriate electrode geometries and stimulus parameters.