title: Modulatory effects of low- and high-frequency repetitive transcranial magnetic stimulation on visual cortex of healthy subjects undergoing light deprivation.
abstract: The aim of the present study was to explore further the effects of light deprivation (LD) on visual cortex excitability. Healthy subjects reporting reliable induction of phosphenes by occipital transcranial magnetic stimulation (TMS) underwent 60 min of complete LD. Phosphene threshold (PT) was measured before (T0), after 45 min (T1) and 60 min (T2) of LD, and then every 10 min after light re-exposure until recovery to T0 values. Repetitive TMS (rTMS) (at 1 or 10 Hz) was applied in separate sessions during the last 15 min of LD. PTs significantly decreased after 45 min of LD. rTMS differentially modified the effects of 60 min LD on PTs depending on stimulation frequency. One hertz rTMS did not change the decreasing of PT values as observed in baseline condition, but significantly prolonged the time to recover T0 PT values after light re-exposure. By contrast, 10 Hz rTMS significantly increased PT and the time to recover T0 PT values after light re-exposure was shortened. The results of this study show that the modulatory effects of different rTMS frequencies on visual cortex critically depend on the pre-existing excitability state of inhibitory and facilitatory circuits, and provide novel insights into the neurophysiological changes that take place in the visual cortex following functional visual deafferentation.
authors.affiliation: Neurophysiological Unit, University of Palermo, Via G. La Loggia, 1, 90128, Palermo, Italy.
authors.forename: Brigida
authors.initials: B
authors.lastname: Fierro
authors.forename: Filippo
authors.initials: F
authors.lastname: Brighina
authors.forename: Gaetano
authors.initials: G
authors.lastname: Vitello
authors.forename: Aurelio
authors.initials: A
authors.lastname: Piazza
authors.forename: Simona
authors.initials: S
authors.lastname: Scalia
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Giglia
authors.forename: Ornella
authors.initials: O
authors.lastname: Daniele
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology; D010719:Phosphenes / Q000502:physiology; D010775:Photic Stimulation; D012683:Sensory Deprivation / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000502:physiology*