Modeling memory consolidation during posttraining periods in cerebellovestibular learning.
Long-term depression (LTD) at parallel fiber-Purkinje cell (PF-PC) synapses is thought to underlie memory formation in cerebellar motor learning. Recent experimental results, however, suggest that multiple plasticity mechanisms in the cerebellar cortex and cerebellar/vestibular nuclei participate in memory formation. To examine this possibility, we formulated a simple model of the cerebellum with a minimal number of components based on its known anatomy and physiology, implementing both LTD and long-term potentiation (LTP) at PF-PC synapses and mossy fiber-vestibular nuclear neuron (MF-VN) synapses. With this model, we conducted a simulation study of the gain adaptation of optokinetic response (OKR) eye movement. Our model reproduced several important aspects of previously reported experimental results in wild-type and cerebellum-related gene-manipulated mice. First, each 1-h training led to the formation of short-term memory of learned OKR gain at PF-PC synapses, which diminished throughout the day. Second, daily repetition of the training gradually formed long-term memory that was maintained for days at MF-VN synapses. We reproduced such memory formation under various learning conditions. Third, long-term memory formation occurred after training but not during training, indicating that the memory consolidation occurred during posttraining periods. Fourth, spaced training outperformed massed training in long-term memory formation. Finally, we reproduced OKR gain changes consistent with the changes in the vestibuloocular reflex (VOR) previously reported in some gene-manipulated mice.
Graduate School of Informatics and Engineering, and pnas14@neuralgorithm.org.
Tadashi
T
Yamazaki
Brain Science Promotion Division, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan; and.
Soichi
S
Nagao
Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093.
William
W
Lennon
Brain Science Inspired Life Support Research Center, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan;
Shigeru
S
Tanaka
D000222:Adaptation, Physiological; D000818:Animals; D002531:Cerebellum / Q000502:physiology*; D003198:Computer Simulation; D008568:Memory / Q000502:physiology*; D008822:Mice, Transgenic; D008959:Models, Neurological; D009473:Neuronal Plasticity / Q000502:physiology; D011689:Purkinje Cells / Q000502:physiology; D014726:Vestibular Nuclei / Q000502:physiology*
Marr–Albus–Ito theory; cerebellum; memory consolidation; plasticity; posttraining period