Temporally parallel facilitation of same-colored objects beyond spatial selection.

In a probabilistic spatial cueing experiment, we cued one out of four objects/arcs that were arranged in a circle to test whether the cued arc/object would result in strictly object-based processing restricting facilitation of features to the cued object, or whether we observe global feature-based spread across object boundaries. Four arcs flickered at different frequencies, respectively, to evoke steady state visual evoked potentials (SSVEPs), allowing to investigate neural temporal dynamics in the early visual cortex following the presentation of the spatial cue. Initially, all arcs had identical colors and with spatial cue onset switched to a specific color configuration. In one configuration, one uncued arc had the same color as the cued one. We found global feature-based spread to same-colored elements across object boundaries in SSVEPs and behavioral responses. Once spatial attention was shifted to the cued location/arc, SSVEP amplitudes elicited by the cued arc and the same-colored uncued arc showed a temporally overlapping increase early after the spatial cue. Importantly, color processing was not required to perform the task, indicating that global feature-based spread occurs automatically, independent of task demands.