Poster B136, Sunday, March 26, 8:00 – 10:00 am, Pacific Concourse
Model-free population receptive field profile estimates reveal information about orientation and ellipticity in early visual areas.
Christian Merkel1, Jens-Max Hopf1,2, Mircea Ariel Schoenfeld1,2; 1Otto-von-Guericke University, Magdeburg, 2Leibniz Institute for Neurobiology, Magdeburg
Estimates of visual field topographies in human visual cortex obtained through fMRI travelling wave techniques usually provide the parameters of population receptive field (pRF) location (polar angle, eccentricity) as well as receptive field size. These parameters are obtained by fitting the recorded data to a standard model population receptive field. In the current work pRF profiles are measured directly by back-projecting preprocessed fMRI time series to sweeps of a bar across the visual field in different angles. These model-free pRF profiles not only contain information about receptive field location and size but also about the pRF shape characteristics. The current data suggests that the elongation (ellipticity) of pRFs decreases across the early visual hierarchy to a different degree for the ventral and the dorsal stream. This suggests that the information on parvo- and magnocellular pathway properties is preserved at a population-level. Furthermore, ellipticity changes as a function of eccentricity. pRF orientation shows a high degree of collinearity with its angular position, which could be observed in particular within area V2. Using model-free pRF measurements, the traveling wave technique provides additional characteristics of pRF topographies that are not restricted to size.
Topic Area: PERCEPTION & ACTION: Vision