Overlap of attention and movement-related activity in lateralized event-related brain potentials

Objective: In tasks that involve lateralized visuospatial attention and a l ateralized motor response, the associated brain electrical potentials, i.e, the attention-related N2pc and the lateralized readiness potential, typica lly overlap at central scalp sites. The manifestation of the N2pc at centra l electrode sites is commonly attributed to electric volume conduction effe cts, assuming the N2pc to be generated in occipito-temporal brain areas. We evaluated this explanation in a simulation study. Methods: Using a forward modeling approach with a realistically shaped volu me conduction model, we calculated the range of amplitude ratios between oc cipital and central electrode sites when a single source is assumed in area V4 or in area TO, at the temporo-occipital convexity. Results: A comparison of the simulated amplitude ratios with reported data indicates that volume conduction effects from the investigated source origi ns in the occipito-temporal region are insufficient to explain the experime ntal data. Conclusions: We conclude that the anterior spread of the N2pc from its occi pito-temporal maximum to central electrode sites is probably due to simulta neous attention-related activity in posterior and central brain areas. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.