title: The chronometry of visual perception: review of occipital TMS masking studies.
abstract: Transcranial magnetic stimulation (TMS) continues to deliver on its promise as a research tool. In this review article we focus on the application of TMS to early visual cortex (V1, V2, V3) in studies of visual perception and visual awareness. Depending on the asynchrony between visual stimulus onset and TMS pulse (SOA), TMS can suppress visual perception, allowing one to track the time course of functional relevance (chronometry) of early visual cortex for vision. This procedure has revealed multiple masking effects ('dips'), some consistently (∼+100ms SOA) but others less so (∼-50ms, ∼-20ms, ∼+30ms, ∼+200ms SOA). We review the state of TMS masking research, focusing on the evidence for these multiple dips, the relevance of several experimental parameters to the obtained 'masking curve', and the use of multiple measures of visual processing (subjective measures of awareness, objective discrimination tasks, priming effects). Lastly, we consider possible future directions for this field. We conclude that while TMS masking has yielded many fundamental insights into the chronometry of visual perception already, much remains unknown. Not only are there several temporal windows when TMS pulses can induce visual suppression, even the well-established 'classical' masking effect (∼+100ms) may reflect more than one functional visual process.
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200MD Maastricht, The Netherlands; Maastricht Brain Imaging Center, PO Box 616, 6200MD Maastricht, The Netherlands. Electronic address: tom.degraaf@maastrichtuniversity.nl.
authors.forename: Tom A
authors.initials: TA
authors.lastname: de Graaf
authors.affiliation: Centre for Cognitive Neuroscience and Department of Psychology, University of Turku, FIN-20014 Turku, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Koivisto
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200MD Maastricht, The Netherlands; Maastricht Brain Imaging Center, PO Box 616, 6200MD Maastricht, The Netherlands; Department of Psychology, Faculty of Science and Technology, University of Westminster, 309 Regent Street, W1B 2HW London, United Kingdom.
authors.forename: Christianne
authors.initials: C
authors.lastname: Jacobs
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, PO Box 616, 6200MD Maastricht, The Netherlands; Maastricht Brain Imaging Center, PO Box 616, 6200MD Maastricht, The Netherlands.
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Sack
mesh_terms: D000818:Animals; D006801:Humans; D009778:Occipital Lobe / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014796:Visual Perception / Q000502:physiology*
keywords: Chronometry; Conscious vision; Early visual cortex; Feedback; Masking; Suppression; Transcranial magnetic stimulation (TMS); Unconscious vision; Visual perception