September 2021
Volume 21, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2021
The Temporal Clocking Rates of Where (Dorsal) and What (Ventral) Visual Systems: Measurement of Motion and Color-Hue Direction Thresholds
Author Affiliations & Notes
  • R. Chandler Krynen
  • Michael K. McBeath
    Max Planck Institute for Empirical Aesthetics
  • Footnotes
    Acknowledgements  ASU SciHub
Journal of Vision September 2021, Vol.21, 2833. doi:
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      R. Chandler Krynen, Michael K. McBeath; The Temporal Clocking Rates of Where (Dorsal) and What (Ventral) Visual Systems: Measurement of Motion and Color-Hue Direction Thresholds. Journal of Vision 2021;21(9):2833.

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

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Introduction: We tested stimulus discrimination speeds associated with the Where (Dorsal Stream) and What (Ventral Stream) visual processing systems. The dual-stream model of neural processing specifies that the Where System is used for rapid perception-action and general motion-processing tasks, while the What System is used to distinguish object related information like type and color. Our study measures the fastest rates for discriminating motion and hue direction, as respective metrics of Where and What System processing speeds. Method: To measure the Where System processing rate, four LEDs, arranged in a diamond configuration, were successively flashed on and off in either clockwise or counter clockwise direction. Ten participants judged direction, with presentation speed following a staircase procedure to determine temporal thresholds. To measure the What System processing rate, a disk lit with equal luminance LEDs successively cycled through the hue circle in either CW or CCW direction (red-green-blue… or red-blue-green-…). The same participants judged hue change direction, again with a temporal staircase procedure. Results: The mean speed threshold for processing CW vs CCW direction was statistically the same for all colors at 19.15 Hz per cycle (equals 76.60 individual LED flashes per second). The mean speed threshold for processing hue direction was 2.28 Hz per cycle (equals 6.84 individual colors per second). The two processing speed rates statistically differed (Δµ=16.87Hz, t(9) = 11.31, p<0.001, d=4.97). Discussion: Our findings support a Where System processing rate of around 20 Hz, consistent with classic findings of flicker fusion rates. They also support a What System processing rate of about 7 Hz consistent with preferred temporal rates of higher level cognitive processes like shape discrimination judgments and preferred speech syllable rate. These findings support the distinction of two visual processing systems and provide a metric for neural research that examines relative dorsal and ventral processing rates.


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