title: Motion area V5/MT+ response to global motion in the absence of V1 resembles early visual cortex.
abstract: Motion area V5/MT+ shows a variety of characteristic visual responses, often linked to perception, which are heavily influenced by its rich connectivity with the primary visual cortex (V1). This human motion area also receives a number of inputs from other visual regions, including direct subcortical connections and callosal connections with the contralateral hemisphere. Little is currently known about such alternative inputs to V5/MT+ and how they may drive and influence its activity. Using functional magnetic resonance imaging, the response of human V5/MT+ to increasing the proportion of coherent motion was measured in seven patients with unilateral V1 damage acquired during adulthood, and a group of healthy age-matched controls. When V1 was damaged, the typical V5/MT+ response to increasing coherence was lost. Rather, V5/MT+ in patients showed a negative trend with coherence that was similar to coherence-related activity in V1 of healthy control subjects. This shift to a response-pattern more typical of early visual cortex suggests that in the absence of V1, V5/MT+ activity may be shaped by similar direct subcortical input. This is likely to reflect intact residual pathways rather than a change in connectivity, and has important implications for blindsight function. It also confirms predictions that V1 is critically involved in normal V5/MT+ global motion processing, consistent with a convergent model of V1 input to V5/MT+. Historically, most attempts to model cortical visual responses do not consider the contribution of direct subcortical inputs that may bypass striate cortex, such as input to V5/MT+. We have shown that the signal change driven by these non-striate pathways can be measured, and suggest that models of the intact visual system may benefit from considering their contribution.
authors.affiliation: 1 FMRIB Centre, University of Oxford, UK 2 Nuffield Department of Clinical Neurosciences, University of Oxford, UK sara.ajina@ndcn.ox.ac.uk.
authors.forename: Sara
authors.initials: S
authors.lastname: Ajina
authors.affiliation: 2 Nuffield Department of Clinical Neurosciences, University of Oxford, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Kennard
authors.affiliation: 3 Wellcome Trust Centre for Neuroimaging, University College London, UK 4 Institute of Cognitive Neuroscience, University College London, UK.
authors.forename: Geraint
authors.initials: G
authors.lastname: Rees
authors.affiliation: 1 FMRIB Centre, University of Oxford, UK 2 Nuffield Department of Clinical Neurosciences, University of Oxford, UK.
authors.forename: Holly
authors.initials: H
authors.lastname: Bridge
mesh_terms: D000328:Adult; D000368:Aged; D001766:Blindness / Q000473:pathology / Q000503:physiopathology; D001930:Brain Injuries / Q000150:complications / Q000473:pathology*; D016022:Case-Control Studies; D005133:Eye Movements; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D010468:Perceptual Disorders / Q000209:etiology*; D010775:Photic Stimulation; D014793:Visual Cortex / Q000503:physiopathology*; D014794:Visual Fields / Q000502:physiology; D014795:Visual Pathways / Q000503:physiopathology
keywords: functional MRI; hemianopia; motion coherence; subcortical; visual cortex