Hello,
Please join us tomorrow at 11am for this week's YNiC seminar (Wednesday 13th). We have an external speaker Dr Marc Himmelberg from New York University who will be presenting a talk titled "Linking cortical magnification in primary visual cortex to visual perception and neural encoding" (see below for the talk abstract).
Many thanks,
Jennifer
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Linking cortical magnification in primary visual cortex to visual perception and neural encoding
Human visual cortex preserves the structure of the retinal image in cortical maps. fMRI has made it possible to measure these retinotopic maps from visually evoked activity in the visual cortex, including primary visual cortex (V1). Cortical magnification (i.e., mm2 of V1 surface area/deg2 visual space) can be measured by combining fMRI retinotopic maps with MRI measurements of cortical surface area. Cortical magnification is greatest at the center of the V1 visual field representation and declines with eccentricity. Cortical magnification also markedly varies with polar angle; it is greater at the horizontal than vertical, and lower than upper vertical meridian of V1 visual field representation. Further, V1 cortical magnification varies up to 3-fold when comparing among individual observers. I will present two projects that harness this location- and observer-dependent variability in cortical magnification to better understand the link between the organisation of V1 and: (1) visual perception; and (2) neural encoding. First, I will present work showing that, when measured as a function of polar angle, V1 cortical magnification parallels behavioural measurements of contrast sensitivity at the group and individual level, demonstrating a tight link between brain and behaviour. Second, I will present recent work showing that a 2D model accounts for location-dependent variation in V1 neural properties –cortical magnification and preferred spatial frequency. I will then show that V1 cortical magnification and preferred spatial frequency covary –and scale– to different extents when measured as a function of eccentricity, polar angle, and individual observer, demonstrating a link between V1 neural resources and neural encoding.
Jennifer Ashton, PhD
Senior Research Technician