title: Cerebellum as a forward but not inverse model in visuomotor adaptation task: a tDCS-based and modeling study.
abstract: Despite several pieces of evidence, which suggest that the human brain employs internal models for motor control and learning, the location of these models in the brain is not yet clear. In this study, we used transcranial direct current stimulation (tDCS) to manipulate right cerebellar function, while subjects adapt to a visuomotor task. We investigated the effect of this manipulation on the internal forward and inverse models by measuring two kinds of behavior: generalization of training in one direction to neighboring directions (as a proxy for inverse models) and localization of the hand position after movement without visual feedback (as a proxy for forward model). The experimental results showed no effect of cerebellar tDCS on generalization, but significant effect on localization. These observations support the idea that the cerebellum is a possible brain region for internal forward, but not inverse model formation. We also used a realistic human head model to calculate current density distribution in the brain. The result of this model confirmed the passage of current through the cerebellum. Moreover, to further explain some observed experimental results, we modeled the visuomotor adaptation process with the help of a biologically inspired method known as population coding. The effect of tDCS was also incorporated in the model. The results of this modeling study closely match our experimental data and provide further evidence in line with the idea that tDCS manipulates FM's function in the cerebellum.
authors.affiliation: Biomedical Engineering Department, Amirkabir University of Technology, Tehran, Iran.|Neurocognitive Laboratory, Iranian National Center for Addiction Studies (INCAS), Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Yavari
authors.affiliation: Biomedical Engineering Department, Amirkabir University of Technology, Tehran, Iran.
authors.forename: Shirin
authors.initials: S
authors.lastname: Mahdavi
authors.affiliation: Biomedical Engineering Department, Amirkabir University of Technology, Tehran, Iran.
authors.forename: Farzad
authors.initials: F
authors.lastname: Towhidkhah
authors.affiliation: Biomedical Engineering Department, Amirkabir University of Technology, Tehran, Iran.
authors.forename: Mohammad-Ali
authors.initials: MA
authors.lastname: Ahmadi-Pajouh
authors.affiliation: Neurocognitive Laboratory, Iranian National Center for Addiction Studies (INCAS), Tehran University of Medical Sciences, Tehran, Iran.|Translational Neuroscience Program, Institute for Cognitive Science Studies (ICSS), Tehran, Iran.|Neuroimaging and Analysis Group, Research Center for Molecular and Cellular Imaging (RCMCI), Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hamed
authors.initials: H
authors.lastname: Ekhtiari
authors.affiliation: Department of Psychology, McGill University, 1205 Dr. Penfield, Room W7/8, Montreal, QC, Canada. mohammad.darainy@mcgill.ca.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Darainy
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D002531:Cerebellum / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D010775:Photic Stimulation / Q000379:methods*; D011597:Psychomotor Performance / Q000502:physiology*; D011897:Random Allocation; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: Cerebellum; Finite element analysis; Internal forward model; Internal inverse model; Population coding; Visuomotor adaptation; tDCS