Abstract: We ask what cerebellum and basal ganglia “do,” arguing that cerebellum tunes motor schemas and their coordination. We argue for a synthesis of models addressing the real-time role and error signaling roles of climbing fibers. “Synthetic PET” bridges between regional and neurophysiological studies, while “synaptic eligibility” relates the neurochemistry of learning to neural and behavioral levels, [CRÉPEL et al.; HOUK et al.; KANO; LINDEN; SIMPSON et al.; SMITH; THACH; VINCENT]

1. Does the cerebellum control muscles or tune motor schemas? SMITH (sect. 2.2, para. 5) tells us that the mutant mouse Lurcher, in which no Purkinje cells survive beyond early adulthood, “show deficits in both the ability to simultaneously (e.g., asynergia) and sequentially (e.g., dysdiadocokinesia) command the desired muscle synergies.” However, the spinal cat can walk on a treadmill if properly supported and stimulated, and so I would argue that cerebellum serves to adjust the spinal motor schema for walking rather than “commanding” the muscle synergies (For clarity, I will reserve “synergy” for this sense of “muscle synergy,” and “motor schema” for a task-specific “program” of coordinated motor control.) Earlier, SMITH notes “The locomotion was very ataxic and the frequent interruptions from a loss of equilibrium accounted for the absence of modulation in the contralateral limb”; moreover (Smith, personal communication), Lurcher mice can coordinate their limbs for swimming.