Bloch's law and the dynamics of feature fusion.

How the visual brain integrates temporally dispersed information is an open question. Often, it is assumed that the visual system simply sums light over a certain period of time (e.g. Bloch's law). However, in feature fusion, information presented later dominates, suggesting complex temporal dynamics that cannot be described by simple energy summation. For example, if two verniers are presented in rapid succession at the same location, they are not perceived individually but they fuse to one single vernier. The perceived offset of the fused vernier is a combination of the offsets of the two presented verniers, with the later one dominating. Here, we show that indeed, Bloch's law does not hold across verniers in a sequence. However, changes in the luminance of a single vernier can be compensated for by changes in its duration in accordance with Bloch's law. We present a simple model to demonstrate that these findings can be explained by decaying neural activation.