title: Stimulation of the human motor cortex alters generalization patterns of motor learning.
abstract: It has been hypothesized that the generalization patterns that accompany learning carry the signatures of the neural systems that are engaged in that learning. Reach adaptation in force fields has generalization patterns that suggest primary engagement of a neural system that encodes movements in the intrinsic coordinates of joints and muscles, and lesser engagement of a neural system that encodes movements in the extrinsic coordinates of the task. Among the cortical motor areas, the intrinsic coordinate system is most prominently represented in the primary sensorimotor cortices. Here, we used transcranial direct current stimulation (tDCS) to alter mechanisms of synaptic plasticity and found that when it was applied to the motor cortex, it increased generalization in intrinsic coordinates but not extrinsic coordinates. However, when tDCS was applied to the posterior parietal cortex, it had no effects on learning or generalization in the force field task. The results suggest that during force field adaptation, the component of learning that produces generalization in intrinsic coordinates depends on the plasticity in the sensorimotor cortex.
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA. jean-jacques.orban@uclouvain.be
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Orban de Xivry
authors.forename: Mollie K
authors.initials: MK
authors.lastname: Marko
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Pekny
authors.forename: Damien
authors.initials: D
authors.lastname: Pastor
authors.forename: Jun
authors.initials: J
authors.lastname: Izawa
authors.forename: Pablo
authors.initials: P
authors.lastname: Celnik
authors.forename: Reza
authors.initials: R
authors.lastname: Shadmehr
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D004558:Electric Stimulation; D005260:Female; D005793:Generalization, Psychological / Q000502:physiology*; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D010296:Parietal Lobe / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D013569:Synapses / Q000502:physiology