August 2023
Volume 23, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2023
Contextual Modulation of Sensory Encoding in the Tilt Illusion
Author Affiliations
  • Ling-Qi Zhang
    University of Pennsylvania
  • Alan A. Stocker
    University of Pennsylvania
Journal of Vision August 2023, Vol.23, 5551. doi:
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      Ling-Qi Zhang, Alan A. Stocker; Contextual Modulation of Sensory Encoding in the Tilt Illusion. Journal of Vision 2023;23(9):5551.

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

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The perceived orientation of a grating is dependent on its surrounding orientation. This “tilt illusion” (Gibson, 1937) is one of the examples demonstrating how perception is influenced by both the spatial and temporal context (Schwartz, Hsu & Dayan, 2007). Explanations of these effects tend to focus on the mechanism by which the response properties of sensory neurons, such as gain and tuning preferences, are modified in response to stimulus context (Clifford, 2014). However, linking changes in neural encoding to behavior is difficult because it requires specific assumptions regarding both how stimulus information is represented (i.e., encoded) but also how it is interpreted (i.e., decoded). Here, we present a method that allows us to directly characterize the contextual modulations of sensory encoding based on psychophysical behavior in a tilt-illusion experiment. Participants in the experiment were asked to estimate the orientation of briefly presented (1500 ms, with 1 Hz contrast modulation) sine wave grating stimuli by rotating a line probe. Gratings were presented within a stimulus surround consisting of either non-oriented filtered noise, or gratings with one of two possible fixed orientations (+/- 30 degree off vertical). We extracted sensory encoding accuracy, based on the lawful relationship between perceptual bias, variance, and Fisher information, with only minimal assumptions about decoding. We found that for a non-oriented surround, sensory encoding accurately reflected the statistics of visual orientations in natural scenes. However, with oriented stimulus surrounds, encoding accuracy was significantly boosted at the corresponding surround orientation yet slightly reduced for neighboring orientations. Our results are consistent with the notion that contextual modulations of sensory encoding represent a form of efficient coding where encoding accuracy is optimized toward the conditional stimulus statistics within the specific context. Lastly, our method is generally applicable to estimate sensory encoding accuracy in other contexts and for other perceptual variables.


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