BACKGROUND: Motion perception may be preserved after damage to striate cortex (primary visual cortex, area V1). Awareness and normal discrimination of fast-moving stimuli have been observed even in the complete absence of V1. These facts suggest that motion-sensitive cortex (the V5/MT complex or V5/MT+) may be activated by direct thalamic or collicular inputs that bypass V1. Such projections have been identified previously in monkeys but have not been shown in humans using neuroimaging techniques. METHODS: We used diffusion tensor imaging (DTI) tractography to visualize white matter fiber tracts connecting with V5/MT+ in 10 healthy volunteers. V5/MT+ was localized for each subject using functional MRI (fMRI). Functional activity maps were overlaid on high-resolution anatomical images and registered with the diffusion-weighted images to define V5/MT+ as the region of interest (ROI) for DTI tractography analysis. Fibers connecting to V1 were excluded from the analysis. RESULTS: Using conservative tractography parameters, we found connections between the V5/MT+ region and the posterior thalamus and/or superior colliculus in 4 of 10 subjects. CONCLUSIONS: Connections between the V5/MT+ region and the posterior thalamus and/or superior colliculus may explain visual motion awareness in the absence of a functioning V1.
BACKGROUND: Motion perception may be preserved after damage to striate cortex (primary visual cortex, area V1). Awareness and normal discrimination of fast-moving stimuli have been observed even in the complete absence of V1. These facts suggest that motion-sensitive cortex (the V5/MT complex or V5/MT+) may be activated by direct thalamic or collicular inputs that bypass V1. Such projections have been identified previously in monkeys but have not been shown in humans using neuroimaging techniques. METHODS: We used diffusion tensor imaging (DTI) tractography to visualize white matter fiber tracts connecting with V5/MT+ in 10 healthy volunteers. V5/MT+ was localized for each subject using functional MRI (fMRI). Functional activity maps were overlaid on high-resolution anatomical images and registered with the diffusion-weighted images to define V5/MT+ as the region of interest (ROI) for DTI tractography analysis. Fibers connecting to V1 were excluded from the analysis. RESULTS: Using conservative tractography parameters, we found connections between the V5/MT+ region and the posterior thalamus and/or superior colliculus in 4 of 10 subjects. CONCLUSIONS: Connections between the V5/MT+ region and the posterior thalamus and/or superior colliculus may explain visual motion awareness in the absence of a functioning V1.
Authors: Maria Barleben; Christian M Stoppel; Jörn Kaufmann; Christian Merkel; Thoralf Wecke; Michael Goertler; Hans-Jochen Heinze; Jens-Max Hopf; Mircea A Schoenfeld Journal: Hum Brain Mapp Date: 2014-12-19 Impact factor: 5.038
Authors: Barry M Seemungal; Jessica Guzman-Lopez; Qadeer Arshad; Simon R Schultz; Vincent Walsh; Nada Yousif Journal: Cereb Cortex Date: 2012-01-30 Impact factor: 5.357
Authors: Alexis Hervais-Adelman; Lore B Legrand; Minye Zhan; Marco Tamietto; Beatrice de Gelder; Alan J Pegna Journal: Front Integr Neurosci Date: 2015-10-22