title: Shining new light on dark percepts: visual sensations induced by TMS.
abstract: Phosphenes induced by transcranial magnetic stimulation (TMS) are sensations of light, whereas a missing region in the visual field induced by TMS is generally referred to as a scotoma. It is believed that phosphenes are caused by neural excitation, while scotomas are due to neural inhibition. In light of the recent literature it might, however, be surmised that both phenomena are the result of neural noise injected into the cortex by TMS and that the likelihood of perceiving the two kinds of percepts depends on the state of the cortex at the time of stimulation. In the present study, TMS was applied over the left occipital cortex under different background conditions (Experiments 1-2) and using different TMS intensities (Experiment 3). Behavioral responses indicate the visual system processes luminance in a standardized manner, as lighter percepts were reacted to faster than darker percepts; this effect, however, did not extend to percept size. Our results suggest that phenomenological characteristics of artificial visual percepts are in line with the proposed effects of TMS as the induction of random neural noise interfering with the neural dynamics (the state of the cortex) at the time of stimulation.
authors.affiliation: University of Verona and National Institute of Neuroscience, Verona, Italy.|Perception and Awareness (PandA) Laboratory, Department of Neurological and Movement Sciences, Section of Physiology and Psychology, University of Verona, Strada le Grazie, 8, 37134, Verona, Italy.
authors.forename: Ramisha
authors.initials: R
authors.lastname: Knight
authors.affiliation: University of Verona and National Institute of Neuroscience, Verona, Italy.|Perception and Awareness (PandA) Laboratory, Department of Neurological and Movement Sciences, Section of Physiology and Psychology, University of Verona, Strada le Grazie, 8, 37134, Verona, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Mazzi
authors.affiliation: University of Verona and National Institute of Neuroscience, Verona, Italy. silvia.savazzi@univr.it.|Perception and Awareness (PandA) Laboratory, Department of Neurological and Movement Sciences, Section of Physiology and Psychology, University of Verona, Strada le Grazie, 8, 37134, Verona, Italy. silvia.savazzi@univr.it.
authors.forename: Silvia
authors.initials: S
authors.lastname: Savazzi
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008027:Light; D008297:Male; D010719:Phosphenes / Q000502:physiology*; D010775:Photic Stimulation; D012684:Sensory Thresholds / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014794:Visual Fields / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Phosphene; Psychological phenomena; Visual perception