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

Objective: In tasks that involve lateralized visuospatial attention and a lateralized motor response, the associated brain electrical potentials, i.e. the attention-related N2pc and the lateralized readiness potential, typically overlap at central scalp sites. The manifestation of the N2pc at central electrode sites is commonly attributed to electric volume conduction effects, 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 volume conduction model, we calculated the range of amplitude ratios between occipital 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 origins in the occipito-temporal region are insufficient to explain the experimental data. Conclusions: We conclude that the anterior spread of the N2pc from its occipito-temporal maximum to central electrode sites is probably due to simultaneous attention-related activity in posterior and central brain areas.