Motion area V5/MT+ response to global motion in the absence of V1 resembles early visual cortex

• Published in: Brain (London, England : 1878) Vol. 138; no. Pt 1; pp. 164 - 178
• Main Authors: Ajina, Sara, Kennard, Christopher, Rees, Geraint, Bridge, Holly
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-01-2015
• Subjects: Adult; Aged; Blindness - pathology; Blindness - physiopathology; Brain Injuries - complications; Brain Injuries - pathology; Case-Control Studies; Eye Movements; Female; Functional Laterality - physiology; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; Middle Aged; Motion Perception - physiology; Original; Perceptual Disorders - etiology; Photic Stimulation; Visual Cortex - physiopathology; Visual Fields - physiology; Visual Pathways - physiopathology; subcortical; functional MRI; hemianopia; motion coherence; visual cortex
• ISSN: 0006-8950; 1460-2156
• DOI: 10.1093/brain/awu328

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.