September 2019
Volume 19, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2019
Long-term spatial memory representations in human visual cortex
Author Affiliations & Notes
  • Serra E Favila
    Department of Psychology, New York University
  • Brice A Kuhl
    Department of Psychology, University of Oregon
  • Jonathan Winawer
    Department of Psychology, New York University
Journal of Vision September 2019, Vol.19, 291c. doi:https://doi.org/10.1167/19.10.291c
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      Serra E Favila, Brice A Kuhl, Jonathan Winawer; Long-term spatial memory representations in human visual cortex. Journal of Vision 2019;19(10):291c. doi: https://doi.org/10.1167/19.10.291c.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Space is a primary organizing dimension in the visual system, with over 20 visual field maps identified in human neocortex. Activity evoked in neocortical areas during perception is thought to be reinstated during later memory retrieval. Memory-driven activity is unlikely to be identical to perceptual activity, but how it differs is unknown. We used fMRI to investigate whether and how remembering learned visual stimuli evokes topographically organized responses in many visual areas. We first trained human subjects to associate colored fixation dot cues with spatially localized stimuli. Stimuli were four unique radial frequency patterns presented at 45°, 135°, 225°, or 315° of polar angle and 2° eccentricity, each paired with a different fixation color. After subjects demonstrated reliable memory performance, we collected fMRI data while subjects either viewed or recalled these stimuli in separate scans. We used population receptive field (pRF) models estimated from independent data to evaluate the BOLD response during memory retrieval as a function of preferred visual field location. We found that memory reactivation is precisely retinotopically mapped, with peak activation during memory at cortical locations whose pRF centers matched the location of the remembered stimulus. There were also clear systematic differences between perception and memory. Memory activation was lower amplitude than visual activation, and this difference was largest for early visual areas. Further, while the spatial profile of visually-driven responses became increasingly broad in higher visual areas (V1: 51°; V3ab: 148°, FWHM), the spatial profile during memory retrieval was similarly broad in all visual areas measured (V1: 123°; V3ab: 109°). We simulated a simple hierarchical model of cortical feedforward and feedback responses that may account for these observations. Our findings support the hypothesis that memory representations make use of sensory maps, but point to differences in how feedforward and feedback activity may propagate through this system.

Acknowledgement: NIH Blueprint D-SPAN F99/K00 Award 
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