Society for Neuroscience Abstracts, 1999

FUNCTIONALLY INDEPENDENT COMPONENTS OF EARLY VISUAL EVENT-RELATED POTENTIALS

M. Westerfield*‡, S. Makeig†, J. Townsend‡, T-P. Jung. §§ and T. J. Sejnowski‡§. ‡Children's Hospital Research Center, †Naval Health Research Center, §Howard Hughes Medical Institute and Salk Institute, §§ Institute for Neural Computation, University of California San Diego

We demonstrate a decomposition of the N1 complex in a visual selective attention paradigm into functionally independent subcomponents with functionally distinct relations to task and stimulus conditions. ERPs were collected from 20 subjects in response to visual target and nontarget stimuli presented at five attended and non-attended screen locations. Independent Component Analysis (ICA) was performed on 500-msec grand average responses from all 25 stimulus/attention conditions and decomposed the nontarget N1 complexes into five spatially fixed, temporally independent and physiologically plausible components. Activity of an early, laterally symmetric component pair (N1a_R and N1a_L) was evoked by left and right visual field stimuli respectively. Component N1a_R peaked ~9 msec earlier than N1a_L. Stimuli in the right visual field evoked activity in a spatiotemporally overlapping bilateral component (N1b) that peaked at around 180 msec and was strongly enhanced by attention. Stimuli presented in unattended locations only evoked a fourth component (P2a) peaking near 240 msec. A fifth component (P3f) was evoked only by targets presented in either visual field. The distinct response patterns of these components across the array of stimulus and attention conditions suggest that they reflect activity in functionally independent brain systems involved in processing attended and unattended visuospatial events.

Research supported by the Office of Naval Research, Howard Hughes Medical Institute, National Institutes of Health and the Swartz Foundation.

 

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