Cortical Cell Assemblies: A Possible Mechanism for Motor Programs

Abstract

The concept of a motor program has been used to interpret a diverse range of empirical findings related to preparation and initiation of voluntary movement. In the absence of an underlying mechanism, its exploratory power has been limited to that of an analogy with running a stored computer program. We argue that the theory of cortical cell assemblies suggests a possible neural mechanism for motor programming. According to this view, a motor program may be conceptualized as a cell assembly, 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 assembly is ignited. The dynamics of cell assembly ignition are considered in relation to the problem of serial order. These considerations lead to a plausible neural mechanism for the programming of movements and movement sequences that is compatible with the effects of precue information and sequence length on reaction times. Anatomical and physiological guidelines for future quantitative models of cortical cell assemblies are suggested. By taking into account the parallel re-entrant loops between the cerebral cortex and basal ganglia, the theory of cortical 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.

Bradykinesia Induced by Dopamine D2 Receptor Blockade Is Associated with Reduced Motor Cortex Activity in the Rat

“…Together, the reduced baseline and task-related firing rates and indices of bursting and synchronization are consistent with disordered recruitment of cortical cell assemblies (Wickens et al, 1994), secondary to impaired basal ganglia-thalamocortical loop function (Voloshin et al, 1994;Pessiglione et al, 2005). In turn, task-related bursts of activity in motor cortex neurons are directly involved in coding force output by muscles (Evarts, 1968;Smith et al, 1975;Cheney and Fetz, 1980;Evarts et al, 1983;Kalaska et al, 1989).…”

Deficit in late-stage contingent negative variation provides evidence for disrupted movement preparation in patients with conversion paresis

“…Such inappropriate right prefrontal activation may thus reflect activation of an (unconscious) inhibitory system that could suppress motor preparation occurring in more caudal motor areas. This would leave motor cortical cell assemblies (Wickens, Hyland, & Anson, 1994) coding the motor program poorly formed or dysfunctional, leading to weakness and RT deficits in conversion paresis.…”

Feature integration across perception and action: event files affect response choice

“…Feature integration is a common theme in visual perception but much less topical in the area of action planning (Stoet & Hommel, 1999, 2002Wickens et al, 1994), and even less with respect to the relation between perception and action planning. However, considering that higher organisms acquire associations between stimuli and responses, the assumption that stimuli as well as responses are represented in terms of distributed feature codes does raise the question of how and according to which principles these features are integrated.…”

“…For instance, the speed of both detecting a visual stimulus and planning an action varies strongly with the number of features the stimulus or action is defined by (see overviews in Wolfe, 1998;Rosenbaum, 1987, respectively), and failures in both perception and action planning often result in featurebased errors (e.g., Treisman & Gelade, 1980;Rosenbaum, Weber, Hazelett, & Hindorff, 1986, respectively). As several authors have pointed out, the existence of distributed representations poses the question of how the distributed codes of a given event are integrated in perception (Treisman, 1996) and action planning (Stoet & Hommel, 1999;Wickens, Hyland, & Anson, 1994).…”