CORTICAL CELL ASSEMBLIES - A POSSIBLE MECHANISM FOR MOTOR PROGRAMS

The concept of a motor program has been used to interpret a diverse ra nge of empirical findings related to preparation and initiation of vol untary movement. In the absence of an underlying mechanism, its explan atory power has been limited to that of an analogy with running a stor ed computer program. We argue that the theory of cortical cell assembl ies suggests a possible neural mechanism for motor programming. Accord ing to this view, a motor program may be conceptualized as a cell asse mbly. which is stored in the form of strengthened synaptic connections between cortical pyramidal neurons. These connections determine which combinations of corticospinal neurons are activated when the cell ass embly is ignited. The dynamics of cell assembly ignition are considere d in relation to the problem of serial order. These considerations lea d to a plausible neural mechanism for the programming of movements and movement sequences that is compatible with the effects of precue info rmation and sequence length on reaction times. Anatomical and physiolo gical guidelines for future quantitative models of cortical cell assem blies are suggested. By taking into account the parallel, re-entrant l oops between the cerebral cortex and basal ganglia. the theory of cort ical cell assemblies suggests a mechanism for motor plans that involve longer sequences. The suggested model is compared with other existing neural network models for motor programming.