Cortical processing and perceived timing

Abstract

As of yet, it is unclear how we determine relative perceived timing. One controversial suggestion is that timing perception might be related to when analyses are completed in the cortex of the brain. An alternate proposal suggests that perceived timing is instead related to the point in time at which cortical analyses commence. Accordingly, timing illusions should not occur owing to cortical analyses, but they could occur if there were differential delays between signals reaching cortex. Resolution of this controversy therefore requires that the contributions of cortical processing be isolated from the influence of subcortical activity. Here, we have done this by using binocular disparity changes, which are known to be detected via analyses that originate in cortex. We find that observers require longer stimulus exposures to detect small, relative to larger, disparity changes; observers are slower to react to smaller disparity changes and observers misperceive smaller disparity changes as being perceptually delayed. Interestingly, disparity magnitude influenced perceived timing more dramatically than it did stimulus change detection. Our data therefore suggest that perceived timing is both influenced by cortical processing and is shaped by sensory analyses subsequent to those that are minimally necessary for stimulus change perception.

Figure 1

Scatter plots (a,c,e) show data for four individual observers. Bar graphs (b,d,f) show data averaged across these observers. Error bars show ±1 s.e. (a) Scatter plot showing temporal detection threshold differences (TT differences), relative to temporal threshold estimates concerning disparity changes of 0.07°, as a function of disparity change magnitude. (b) Average TT differences. (c) Scatter plot showing RT differences, relative to RTs for disparity changes of 0.07°, as a function of disparity change magnitude. (d) Average RT differences. (e) Scatter plot showing perceived synchrony (PS) differences, relative to PS estimates concerning disparity changes of 0.07°, as a function of disparity change magnitude. (f) Average PS differences.