title: Improved motion perception and impaired spatial suppression following disruption of cortical area MT/V5.
abstract: As stimulus size increases, motion direction of high-contrast patterns becomes increasingly harder to perceive. This counterintuitive behavioral result, termed "spatial suppression," is hypothesized to reflect center-surround antagonism-a receptive field property ubiquitous in sensory systems. Prior research proposed that spatial suppression of motion signals is a direct correlate of center-surround antagonism within cortical area MT. Here, we investigated whether human MT/V5 is indeed causally involved in spatial suppression of motion signals. The key assumption is that a disruption of neural mechanisms that play a critical role in spatial suppression could allow these normally suppressed motion signals to reach perceptual awareness. Thus, our hypothesis was that a disruption of MT/V5 should weaken spatial suppression and, consequently, improve motion perception of large, moving patterns. To disrupt MT/V5, we used offline 1 Hz transcranial magnetic stimulation (TMS)-a method that temporarily attenuates normal functioning of the targeted cortex. Early visual areas were also targeted as a control site. The results supported our hypotheses and showed that disruption of MT/V5 improved motion discrimination of large, moving stimuli, presumably by weakening surround suppression strength. This effect was specific to MT/V5 stimulation and contralaterally presented stimuli. Evidently, the critical neural constraints limiting motion perception of large, high-contrast stimuli involve MT/V5. Additionally, our findings mimic spatial suppression deficits that are observed in several patient populations and implicate impaired MT/V5 processes as likely neural correlates for the reported perceptual abnormalities in the elderly, patients with schizophrenia and those with a history of depression.
authors.affiliation: Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY 14627, USA. duje@cvs.rochester.edu
authors.forename: Duje
authors.initials: D
authors.lastname: Tadin
authors.forename: Juha
authors.initials: J
authors.lastname: Silvanto
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
authors.forename: Lorella
authors.initials: L
authors.lastname: Battelli
mesh_terms: D000328:Adult; D006801:Humans; D008279:Magnetic Resonance Imaging; D009039:Motion Perception; D010468:Perceptual Disorders / Q000503:physiopathology / Q000523:psychology; D013028:Space Perception; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000503:physiopathology*; D055815:Young Adult