The Neural Response to Visual Symmetry Is Not Modulated by Visuospatial Attention

Symmetry detection is effortlessly and fast, even within brief presentations of less than 100 milliseconds. Electroencephalographic studies have shown that the brain response to symmetry is automatic and not altered by participant’s task. However, no studies have yet tested whether the symmetry response is altered by the current focus of spatial attention. We adapted the cueing paradigm (Posner, 1980) and recorded a symmetry-related event-related potential known as the sustained posterior negativity (SPN) which is relatively negative for symmetrical compared with random patterns at posterior electrodes. We predicted a stronger SPN when patterns would appear at the attended location than at the unattended location. Forty-eight participants discriminated symmetrical and random-dot patterns that were cued by an endogenous cue (arrow) presented at fixation. To control for covert attention, fixation, measured with an eye-tracking device, was maintained while patterns were presented to both the left and right side of fixation for 1,000 milliseconds. Surprisingly, we found that the SPN amplitude was independent of spatial attention, not changing significantly depending on whether symmetric patterns appeared in a cued or uncued location. This reinforces the understanding of the neural response to symmetry as automatic and stimulus-driven, unchanged by either task or spatial attention.