ERP evidence for human early visual sensitivity to co-linearity compared to co-circularity

Our complex visual environment is constrained by natural geometric regularities, including spatiotemporal regularity, co-linearity and co-circularity. To investigate human visual processing associated with these regularities we directly compared the neural processes in encoding dynamic co-linearity and co-circularity using event-related potentials (ERPs). By recording ERPs to a target bar presented alone (no context) or in a dynamic sequence of bars following a co-linear or co-circular path, we observed earlier ERPs to targets embedded in co-linear sequence at early (66 ms) and later stages (197 ms) of post-target processing. In contrast, targets in co-circular sequence only modulated ERPs at later stages of processing. It is proposed that early visual processing may have adapted to efficiently process co-linearity to improve target identification, whereas sensitivity to co-circularity does not occur until later stages of processing. These results have significant impact for understanding brain-behaviour relationships when processing natural geometric regularities. (C) 2013 Elsevier Ireland Ltd. All rights reserved.