title: Probing V5/MT excitability with transcranial magnetic stimulation following visual motion adaptation to random and coherent motion.
abstract: The response to stimulating the visual cortex with transcranial magnetic stimulation (TMS) depends on its initial activation state, for example, visual motion adaptation biases perceived TMS-induced phosphene characteristics (e.g., color). We quantified this state dependence by assessing the probability of reporting a phosphene (P(λ) ) with "threshold" TMS (i.e., the TMS intensity producing P(λ) = 0.5 at baseline) following visual motion adaptation to a random dot motion display. Postadaptation, P(λ) was increased, and this effect was confined to the adapted neuronal population. We then adapted subjects using a population of moving dots of fixed average motion direction with standard deviations (SD) ranging from 1° to 128° (SD fixed for a given trial). P(λ) was significantly increased at all dot motion SDs except SD = 1°. Neuronal adaptation increases the susceptibility of the neuronal population to activation by threshold intensity TMS. Thus the process of neuronal adaption is not necessarily synonymous with a downmodulation of neuronal excitability.
authors.affiliation: Centre for Neurosciences, Charing Cross Campus, Imperial College, London, United Kingdom.
authors.forename: Jessica
authors.initials: J
authors.lastname: Guzman-Lopez
authors.forename: Juha
authors.initials: J
authors.lastname: Silvanto
authors.forename: Nada
authors.initials: N
authors.lastname: Yousif
authors.forename: Sofia
authors.initials: S
authors.lastname: Nousi
authors.forename: Shamim
authors.initials: S
authors.lastname: Quadir
authors.forename: Barry M
authors.initials: BM
authors.lastname: Seemungal
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009799:Ocular Physiological Phenomena; D010719:Phosphenes / Q000502:physiology; D010775:Photic Stimulation; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000502:physiology*