title: Induced deficits in speed perception by transcranial magnetic stimulation of human cortical areas V5/MT+ and V3A.
abstract: In this report, we evaluate the role of visual areas responsive to motion in the human brain in the perception of stimulus speed. We first identified and localized V1, V3A, and V5/MT+ in individual participants on the basis of blood oxygenation level-dependent responses obtained in retinotopic mapping experiments and responses to moving gratings. Repetitive transcranial magnetic stimulation (rTMS) was then used to disrupt the normal functioning of the previously localized visual areas in each participant. During the rTMS application, participants were required to perform delayed discrimination of the speed of drifting or spatial frequency of static gratings. The application of rTMS to areas V5/MT and V3A induced a subjective slowing of visual stimuli and (often) caused increases in speed discrimination thresholds. Deficits in spatial frequency discrimination were not observed for applications of rTMS to V3A or V5/MT+. The induced deficits in speed perception were also specific to the cortical site of TMS delivery. The application of TMS to regions of the cortex adjacent to V5/MT and V3A, as well as to area V1, produced no deficits in speed perception. These results suggest that, in addition to area V5/MT+, V3A plays an important role in a cortical network that underpins the perception of stimulus speed in the human brain.
authors.affiliation: School of Optometry and Vision Science, University of Bradford, Bradford, West Yorkshire BD7 1DP, United Kingdom. d.mckeefry@bradford.ac.uk
authors.forename: Declan J
authors.initials: DJ
authors.lastname: McKeefry
authors.forename: Mark P
authors.initials: MP
authors.lastname: Burton
authors.forename: Chara
authors.initials: C
authors.lastname: Vakrou
authors.forename: Brendan T
authors.initials: BT
authors.lastname: Barrett
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Morland
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology / Q000528:radiation effects; D004574:Electromagnetic Fields / Q000009:adverse effects; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology* / Q000528:radiation effects; D009415:Nerve Net / Q000033:anatomy & histology / Q000502:physiology / Q000528:radiation effects; D010468:Perceptual Disorders / Q000209:etiology / Q000503:physiopathology*; D010775:Photic Stimulation / Q000379:methods; D012160:Retina / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology / Q000528:radiation effects; D013997:Time Factors; D013998:Time Perception / Q000502:physiology* / Q000528:radiation effects; D050781:Transcranial Magnetic Stimulation / Q000009:adverse effects / Q000379:methods; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology* / Q000528:radiation effects; D014794:Visual Fields / Q000502:physiology / Q000528:radiation effects; D014795:Visual Pathways / Q000033:anatomy & histology / Q000502:physiology / Q000528:radiation effects