title: Adaptation to Leftward Shifting Prisms Alters Motor Interhemispheric Inhibition.
abstract: Adaptation to rightward shifting prisms (rightward prism adaptation, RPA) ameliorates neglect symptoms in patients while adaptation to leftward shifting prisms (leftward prism adaptation, LPA) induces neglect-like behaviors in healthy subjects. It has been hypothesized that prism adaptation (PA) modulates interhemispheric balance between the parietal cortices by inhibiting the posterior parietal cortex (PPC) contralateral to the prismatic deviation, but PA's effects on interhemispheric inhibition (IHI) have not been directly investigated. Since there are hyper-excitable connections between the PPC and primary motor cortex (M1) in the left hemisphere of neglect patients, we reasoned that LPA might mimic right hemisphere lesions by reducing parietal IHI, hyper-exciting the left PPC and PPC-M1 connections, and in turn altering IHI at the motor level. Namely, we hypothesized that LPA would increase IHI from the left to the right M1. We examined changes in left-to-right and right-to-left IHI between the 2 M1s using the ipsilateral silent period (iSP) (Meyer et al. 1995) before and after either LPA or RPA. The iSP was significantly longer after LPA but only from left-to-right and it did not change at all after RPA. This is the first physiological demonstration that LPA alters IHI in the healthy brain.
authors.affiliation: ImpAct team, Lyon Neuroscience Research Center, INSERM U1028, CRNS-UMR5292, 16 Ave. Doyen Lépine, 69676 Bron Cedex, France.|Lyon 1 University, F-69373 Lyon, France.
authors.forename: Elisa
authors.initials: E
authors.lastname: Martín-Arévalo
authors.affiliation: ImpAct team, Lyon Neuroscience Research Center, INSERM U1028, CRNS-UMR5292, 16 Ave. Doyen Lépine, 69676 Bron Cedex, France.|Lyon 1 University, F-69373 Lyon, France.|Behavioral Neurology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Bethesda, MD, USA.
authors.forename: Selene
authors.initials: S
authors.lastname: Schintu
authors.affiliation: ImpAct team, Lyon Neuroscience Research Center, INSERM U1028, CRNS-UMR5292, 16 Ave. Doyen Lépine, 69676 Bron Cedex, France.|Lyon 1 University, F-69373 Lyon, France.|Hospices Civils de Lyon, Neuro-immersion & Mouvement et Handicap, F-69676 Lyon, France.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Farnè
authors.affiliation: ImpAct team, Lyon Neuroscience Research Center, INSERM U1028, CRNS-UMR5292, 16 Ave. Doyen Lépine, 69676 Bron Cedex, France.|Lyon 1 University, F-69373 Lyon, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Pisella
authors.affiliation: ImpAct team, Lyon Neuroscience Research Center, INSERM U1028, CRNS-UMR5292, 16 Ave. Doyen Lépine, 69676 Bron Cedex, France.|Lyon 1 University, F-69373 Lyon, France.
authors.forename: Karen T
authors.initials: KT
authors.lastname: Reilly
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D010296:Parietal Lobe / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D011597:Psychomotor Performance / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: TMS; ipsilateral silent period; prism adaptation; visuospatial neglect