title: A chronometric exploration of high-resolution 'sensitive TMS masking' effects on subjective and objective measures of vision.
abstract: Transcranial magnetic stimulation (TMS) can induce masking by interfering with ongoing neural activity in early visual cortex. Previous work has explored the chronometry of occipital involvement in vision by using single pulses of TMS with high temporal resolution. However, conventionally TMS intensities have been high and the only measure used to evaluate masking was objective in nature. Recent studies have begun to incorporate subjective measures of vision, alongside objective ones. The current study goes beyond previous work in two regards. First, we explored both objective vision (an orientation discrimination task) and subjective vision (a stimulus visibility rating on a four-point scale), across a wide range of time windows with high temporal resolution. Second, we used a very sensitive TMS-masking paradigm: stimulation was at relatively low TMS intensities, with a figure-8 coil, and the small stimulus was difficult to discriminate already at baseline level. We hypothesized that this should increase the effective temporal resolution of our paradigm. Perhaps for this reason, we are able to report a rather interesting masking curve. Within the classical-masking time window, previously reported to encompass broad SOAs anywhere between 60 and 120 ms, we report not one, but at least two dips in objective performance, with no masking in-between. The subjective measure of vision did not mirror this pattern. These preliminary data from our exploratory design suggest that, with sensitive TMS masking, we might be able to reveal visual processes in early visual cortex previously unreported.
authors.affiliation: Faculty of Psychology and Neuroscience, Department of Cognitive Neuroscience, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. tom.degraaf@maastrichtuniversity.nl
authors.forename: Tom A
authors.initials: TA
authors.lastname: de Graaf
authors.forename: Jim
authors.initials: J
authors.lastname: Herring
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Sack
mesh_terms: D001288:Attention / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009433:Neural Inhibition / Q000502:physiology; D009483:Neuropsychological Tests / Q000592:standards; D009949:Orientation / Q000502:physiology; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis; D013997:Time Factors; D013998:Time Perception / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014796:Visual Perception / Q000502:physiology*; D014894:Weights and Measures / Q000592:standards