Nicolas Catz1, Peter W Dicke, Peter Thier. 1. Department of Cognitive Neurology, Center of Neurology, University of Tübingen, Hertie Institute for Clinical Brain Research, Ottfried Müller Strasse 27, 72076 Tübingen, Germany.
Abstract
BACKGROUND: Cerebellar Purkinje cells (PC) generate two responses: the simple spike (SS), with high firing rates (>100 Hz), and the complex spike (CS), characterized by conspicuously low discharge rates (1-2 Hz). Contemporary theories of cerebellar learning suggest that the CS discharge pattern encodes an error signal that drives changes in SS activity, ultimately related to motor behavior. This then predicts that CS will discharge in relation to the error and at random once the error has been nulled by the new behavior. RESULTS: We tested this hypothesis with saccadic adaptation in macaque monkeys as a model of cerebellar-dependent motor learning. During saccadic adaptation, error information unconsciously changes the endpoint of a saccade prompted by a visual target that shifts its final position during the saccade. We recorded CS from PC of the posterior vermis before, during, and after saccadic adaptation. In clear contradiction to the "error signal" concept, we found that CS occurred at random before adaptation onset, i.e., when the error was maximal, and built up to a specific saccade-related discharge profile during the course of adaptation. This profile became most pronounced at the end of adaptation, i.e., when the error had been nulled. CONCLUSIONS: We suggest that CS firing may underlie the stabilization of a learned motor behavior, rather than serving as an electrophysiological correlate of an error.
BACKGROUND: Cerebellar Purkinje cells (PC) generate two responses: the simple spike (SS), with high firing rates (>100 Hz), and the complex spike (CS), characterized by conspicuously low discharge rates (1-2 Hz). Contemporary theories of cerebellar learning suggest that the CS discharge pattern encodes an error signal that drives changes in SS activity, ultimately related to motor behavior. This then predicts that CS will discharge in relation to the error and at random once the error has been nulled by the new behavior. RESULTS: We tested this hypothesis with saccadic adaptation in macaque monkeys as a model of cerebellar-dependent motor learning. During saccadic adaptation, error information unconsciously changes the endpoint of a saccade prompted by a visual target that shifts its final position during the saccade. We recorded CS from PC of the posterior vermis before, during, and after saccadic adaptation. In clear contradiction to the "error signal" concept, we found that CS occurred at random before adaptation onset, i.e., when the error was maximal, and built up to a specific saccade-related discharge profile during the course of adaptation. This profile became most pronounced at the end of adaptation, i.e., when the error had been nulled. CONCLUSIONS: We suggest that CS firing may underlie the stabilization of a learned motor behavior, rather than serving as an electrophysiological correlate of an error.
Authors: Mario Manto; James M Bower; Adriana Bastos Conforto; José M Delgado-García; Suzete Nascimento Farias da Guarda; Marcus Gerwig; Christophe Habas; Nobuhiro Hagura; Richard B Ivry; Peter Mariën; Marco Molinari; Eiichi Naito; Dennis A Nowak; Nordeyn Oulad Ben Taib; Denis Pelisson; Claudia D Tesche; Caroline Tilikete; Dagmar Timmann Journal: Cerebellum Date: 2012-06 Impact factor: 3.847
Authors: P C A van Broekhoven; C K L Schraa-Tam; A van der Lugt; M Smits; M A Frens; J N van der Geest Journal: Cerebellum Date: 2009-05-27 Impact factor: 3.847