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Athena Buckthought, Jeounghoon Kim, Hugh R. Wilson; Hysteresis effects in stereopsis and binocular rivalry. Journal of Vision 2006;6(6):846. doi: 10.1167/6.6.846.
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© ARVO (1962-2015); The Authors (2016-present)
Neural hysteresis plays a fundamental role in stereopsis and reveals the existence of positive feedback at the cortical level (Wilson & Cowan, 1972). Using a model of cortical dynamics, we predicted that it should be possible to measure hysteresis as a function of orientation disparity in tilted gratings in which a transition is perceived between stereopsis and binocular rivalry.
Methods. The patterns were 2 cpd or 4 cpd sinewave gratings with orientation disparities (0–40 deg) resulting in various degrees of tilt. A sequence of 40 pattern pairs was used, with the orientation disparity increased by a fixed increment in successive pairs. During each experimental trial a movie of the 40 pairs was shown at a rate of 0.5, 1 or 2 pairs per second. In separate trials the same movie was shown in reverse order. Two transition points were measured: the point at which the single tilted grating broke into two rivalrous gratings (T1), and the point at which the two rivalrous gratings merged into a single tilted grating (T2).
Results. Transitions occurred at different orientation disparities (T1=24.7 deg, T2=17.8 deg at 2 cpd; T1=27.1 deg, T2=18.0 deg at 4 cpd) corresponding to a timing difference of 3.5–4.6 sec. This was consistent with hysteresis and far exceeded the effects which could be attributed to reaction time or adaptation.
The results are consistent with a cortical model with positive feedback arising from recurrent inhibition between binocular units coding different disparities and orientations. Stereopsis and rivalry are two possible states of the network.
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