Temporal channels and disparity representations in stereoscopic depth perception

Abstract

Stereoscopic depth perception is supported by a combination of correlation-based and match-based representations of binocular disparity. It also relies on both transient and sustained temporal channels of the visual system. Previous studies suggest that the relative contribution of the correlation-based representation (over the match-based representation) and the transient channel (over the sustained channel) to depth perception increases with the disparity magnitude. The mechanisms of the correlation-based and match-based representations may receive preferential inputs from the transient and sustained channels, respectively. We examined near/far discrimination by observers using random-dot stereograms refreshed at various rates. The relative contribution of the two representations was inferred by changing the fraction of dots that were contrast reversed between the two eyes. Both representations contributed to depth discrimination over the tested range of refresh rates. As the rate increased, the correlation-based representation increased its contribution to near/far discrimination. Another experiment revealed that the match-based representation was constructed by exploiting the variability in correlation-based disparity signals. Thus, the relative weight of the transient over sustained channel differs between the two representations. The correlation-based representation dominates depth perception with dynamic inputs. The match-based representation, which may be a nonlinear refinement of the correlation-based representation, exerts more influence on depth perception with slower inputs.

Neurons in Striate Cortex Signal Disparity in Half-Matched Random-Dot Stereograms

“…Nonetheless, since the model prediction was made without any parameter fitting, this success provides strong evidence that V1 cells signal disparity in these stimuli by exploiting fluctuations in local correlation within the RF. Note that if responses to halfmatched stimuli represented a contribution from a pure "matching computation" (Doi et al, 2011(Doi et al, , 2013Abdolrahmani et al, 2016;Henriksen et al, 2016a), the data in Figure 5 should lie on the identity line, which they do not.…”

“…The original binocular energy model does not signal depth in half-matched stereograms because its response varies linearly as a function of binocular correlation. Thus, when the mean binocular correlation is zero, the mean response of the model is equal to its uncorrelated response (although the variability of the response is greater in the halfmatched case; Doi et al, 2013;Doi and Fujita, 2014;Henriksen et al, 2016a). The extent of this variation in binocular correlation will depend on the number of dots contained within the receptive field.…”

“…This analysis does not demonstrate whether the disparity tuning is sufficient to account for psychophysical behavior. We chose our high density (24%) because that value has been used in previous psychophysical studies (Doi et al, 2011(Doi et al, , 2013Henriksen et al, 2016a). If the weak tuning to half-matched stimuli we find with this density is not sufficient to account for psychophysical performance, it might be necessary to postulate a separate matching computation, as hypothesized in the literature (Doi et al, 2011(Doi et al, , 2013Doi and Fujita, 2014).…”

“…However, a series of recent publications by Doi et al (2011Doi et al ( , 2013Doi et al ( , 2014) has suggested that a quite different computation is needed for some stimuli because humans are able to see depth in RDS constructed with an equal number of correlated and anticorrelated dots (termed half-matched RDS; Doi et al, 2011Doi et al, , 2013Doi and Fujita, 2014). The stimulus is illustrated in Figure 1.…”

Disparity processing in primary visual cortex

“…V1 neurons approximately implement a 'correlationbased' computation, but the results with anticorrelated dots indicate that their response is not a linear function of binocular correlation-it is not a 'pure correlation' computation. Recently, an ingenious series of psychophysical experiments by Doi et al [47,48] have demonstrated that human stereo matching in some stimuli cannot be explained by a matching scheme based on pure correlation. They have suggested that this requires two separate matching mechanisms, and show that a model with two mechanisms neatly describes the data [49].…”