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Category: Project

Description: The visual system can detected symmetry automatically and preattentively, however the exact role of attention is unclear. No study has yet explored whether the brain response to symmetry is altered by covert spatial attention. We measured the brain response to symmetry with an ERP known as the sustained posterior negativity (SPN). We conducted two experiments to assess whether the SPN is modulated by voluntary visuospatial attention. On each trial two patterns were presented, one on the left and one on the right of central fixation. A central arrow cue pointed to one of the patterns, and participants judge whether the cued pattern was symmetrical or random. We predicted a stronger contralateral SPN when symmetry appeared in the attended location. This was confirmed. However, surprisingly, there was a large SPN generated by symmetry in the unattended locations. We conclude that whilst the brain response to symmetry is slightly enhanced by voluntary visuospatial attention, it is still strongly present in its absence.