September 2019
Volume 19, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2019
What can be inferred about changes in neural population codes from psychophysical threshold studies?
Author Affiliations
  • Jason Hays
    Florida International University
    Speaker:
  • Fabian A. Soto
    Florida International University
Journal of Vision September 2019, Vol.19, 7. doi:https://doi.org/10.1167/19.10.7
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      Jason Hays, Fabian A. Soto; What can be inferred about changes in neural population codes from psychophysical threshold studies?. Journal of Vision 2019;19(10):7. doi: https://doi.org/10.1167/19.10.7.

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

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Abstract

The standard population encoding/decoding model is now routinely used to study visual representation through psychophysics and neuroimaging. Such studies are indispensable to understand human visual neuroscience, where more invasive techniques are usually not available, but researchers should be careful not to interpret curves obtained from such indirect measures as directly comparable to analogous data from neurophysiology. Here we explore through simulation exactly what kind of inference can be made about changes in neural population codes from observed changes in psychophysical thresholds. We focus on the encoding of orientation by a dense array of narrow-band neural channels, and assume statistically optimal decoding. We explore several mechanisms of encoding change, which could be produced by factors such as attention and learning, and which have been highlighted in the previous literature: (non) specific gain, (non)specific bandwidth-narrowing, inward/outward tuning shifts, and specific suppression with(out) nonspecific gain. We compared the pattern of psychophysical thresholds produced by the model with and without the influence of such mechanisms, in several experimental designs. Each type of model produced a distinctive behavioral pattern, but only if changes in encoding are strong enough and two or more experiments with different designs are performed (i.e., no single experiment can discriminate among all mechanisms). Our results suggest that identifying encoding changes from psychophysics is possible under the right conditions and assumptions and suggest that psychophysical threshold studies are a powerful alternative to neuroimaging in the study of visual neural representation in humans.

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