Cerebellar-dependent motor learning is based on pruning a Purkinje cell population response.
The improvement of motor behavior, based on experience, is a form of learning that is critically dependent on the cerebellum. A well studied example of cerebellar motor learning is short-term saccadic adaptation (STSA). In STSA, information on saccadic errors is used to improve future saccades. The information optimizing saccade metrics is conveyed by Purkinje cells simple spikes (PC-SS) because they are the critical input to the premotor circuits for saccades. We recorded PC-SS of monkeys undergoing STSA to reveal the code used for improving behavior. We found that the discharge of individual PC-SS was unable to account for the behavioral changes. The PC-SS population burst (PB), however, exhibited changes that closely paralleled the qualitatively different changes of saccade kinematics associated with gain-increase and gain-decrease STSA, respectively. Gain-increase STSA, characterized by an increase in saccade duration, replicates the relationship between saccade duration and the end of the PB valid for unadapted saccades. In contrast, gain-decrease STSA, which sports normal saccade duration but reduced saccadic velocity, is characterized by a PB that ends well before the adapted saccade. This suggests that the duration of normal as well as gain-increased saccades is determined by appropriately setting the end of PB end. However, the duration of gain-decreased saccades is apparently not modified by the cerebellum because the PB signals ends too early to determine saccade end. In summary, STSA, and most probably cerebellar-dependent learning in general, is based on optimizing the shape of a PC-SS population response.
Catz
Nicolas
N
Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Hoppe-Seyler Strasse 3, 72076 Tübingen, Germany.
Dicke
Peter W
PW
Thier
Peter
P
D000200:Action Potentials; D000818:Animals; D001522:Behavior, Animal; D001696:Biomechanical Phenomena; D002529:Cerebellar Nuclei; D002531:Cerebellum / Q000473:pathology*; D004594:Electrophysiology; D007858:Learning; D008253:Macaca mulatta; D008954:Models, Biological; D009048:Motor Skills; D009434:Neural Pathways; D011323:Primates; D011689:Purkinje Cells / Q000166:cytology*; D012438:Saccades