11 Neurophysiology / Circuitry

Theories of the role of the basal ganglia within the functional circuitry of the basal ganglia-thalamic-cortical system are entering a state of flux. Current theories, while of heuristic value in explaining many observations, are now inconsistent with an expanding body of knowledge. Most likely, observations supportive of the current theories and their associated circumstances will be found to be special cases of a larger new theory. There is no new general theory yet proposed that is a clear successor. Consequently, there is considerable value in analyzing the epistemic basis of current theories, if for no other reason than avoiding the types of inferences that, in retrospect, are erroneous. Also, such an exercise may help to form a framework by which new theories can develop and be judged. As Charcot said, ‘‘we see only what we are ready to see’’ (1). Typically this statement is made in retrospect to explain why observations and insights are missed or late in being made. A better use would be to prepare prospectively to facilitate new observations and insights. Such preparation must necessarily be theoretical and, to some extent, philosophical because such discussions precede recognition of data. Understanding the functional circuitry of the basal ganglia-thalamuscortex in terms of neuronal activities and interrelationships within a large-