title: Three timescales in prism adaptation.
abstract: It has been proposed that motor adaptation depends on at least two learning systems, one that learns fast but with poor retention and another that learns slowly but with better retention (Smith MA, Ghazizadeh A, Shadmehr R. PLoS Biol 4: e179, 2006). This two-state model has been shown to account for a range of behavior in the force field adaptation task. In the present study, we examined whether such a two-state model could also account for behavior arising from adaptation to a prismatic displacement of the visual field. We first confirmed that an "adaptation rebound," a critical prediction of the two-state model, occurred when visual feedback was deprived after an adaptation-extinction episode. We then examined the speed of decay of the prism aftereffect (without any visual feedback) after repetitions of 30, 150, and 500 trials of prism exposure. The speed of decay decreased with the number of exposure trials, a phenomenon that was best explained by assuming an "ultraslow" system, in addition to the fast and slow systems. Finally, we compared retention of aftereffects 24 h after 150 or 500 trials of exposure: retention was significantly greater after 500 than 150 trials. This difference in retention could not be explained by the two-state model but was well explained by the three-state model as arising from the difference in the amount of adaptation of the "ultraslow process." These results suggest that there are not only fast and slow systems but also an ultraslow learning system in prism adaptation that is activated by prolonged prism exposure of 150-500 trials.
authors.affiliation: Department of Neurophysiology, Graduate School of Medicine, Juntendo University, Bunkyo, Tokyo, Japan;
authors.forename: Masato
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Department of Neurophysiology, Graduate School of Medicine, Juntendo University, Bunkyo, Tokyo, Japan; Dynamic Brain Network Laboratory, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan;
authors.forename: Motoaki
authors.initials: M
authors.lastname: Uchimura
authors.affiliation: Department of Neurophysiology, Graduate School of Medicine, Juntendo University, Bunkyo, Tokyo, Japan;
authors.forename: Ayaka
authors.initials: A
authors.lastname: Karibe
authors.affiliation: Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; ImpAct, Centre des Neurosciences de Lyon, INSERM UMR-S 1028, CNRS UMR 5292, Université Lyon 1, Bron, France;
authors.forename: Jacinta
authors.initials: J
authors.lastname: O'Shea
authors.affiliation: ImpAct, Centre des Neurosciences de Lyon, INSERM UMR-S 1028, CNRS UMR 5292, Université Lyon 1, Bron, France; Plate-forme Mouvement et Handicap, Hospices Civils de Lyon; Centre de Recherche en Neurosciences de Lyon, Service de Rééducation Neurologique, Hôpital Henry Gabrielle, Saint Genis Laval, France;
authors.forename: Yves
authors.initials: Y
authors.lastname: Rossetti
authors.affiliation: Department of Neurophysiology, Graduate School of Medicine, Juntendo University, Bunkyo, Tokyo, Japan; Dynamic Brain Network Laboratory, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan; Department of Brain Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan; and Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology and Osaka University, Suita, Osaka, Japan kitazawa@fbs.osaka-u.ac.jp.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kitazawa
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D056228:Feedback, Sensory; D005260:Female; D006801:Humans; D007909:Lenses; D008297:Male; D008568:Memory; D008875:Middle Aged; D008959:Models, Neurological; D011597:Psychomotor Performance; D011601:Psychophysics; D013997:Time Factors; D014796:Visual Perception; D055815:Young Adult
keywords: motor learning; prism adaptation; reaching; three-state model; two-state model