Detection of temporal structure depends on spatial structure

Observers can more easily detect correlated patterns of temporal contrast m odulation within hybrid visual images composed of two components when those components are drawn from the same original picture (Blake, R., & Yang, Y. (1997). Proceedings of the National Academy of Science, 94, 7115-7119). To learn whether spatial phase is a mediating variable, we measured threshold s for detection of contrast modulation over time among component gratings w hile manipulating spatial phase among those components. In Experiment 1, ob servers more easily detected correlated contrast modulation when two compon ent gratings were aligned in peaks-subtract phase. Experiment 2 showed that this phase-dependent detectability of synchronized contrast modulation is mediated by the phase-dependent, non-linear interaction among spatial frequ ency channels. The rigorous evaluation of several a priori reasonable hypot heses indicates that the phase-dependent detectability is not based on loca l spatial features such as local luminance, contrast or luminance gradient. Taken together, our results indicate that the spatial phase relationship a nd the temporal correlation of contrast modulation of two component grating s are both important for triggering facilitatory interaction between neural analyzers tuned to those gratings. (C) 1999 Elsevier Science Ltd. All righ ts reserved.