Abstracts, Cognitive Neuroscience Society, p. 93, April, 2000
INDEPENDENT COMPONENTS OF EVENT-RELATED ELECTROENCEPHALOGRAPHIC DATA Scott Makeig(1), Sigurd Enghoff(2,5), Tzyy-Ping Jung(3,4) and Terrence J. Sejnowski(2,3,4)
(1) Naval Health Research Center, (2) Salk Institute, (3) Howard Hughes Medical Institute, (4) University of California San Diego, (5) Danish Technical University
Multichannel event-related EEG data, viewed as linear sums of macropotentials generated in functionally independent and spatially fixed brain (or extra-brain) regions, are well-suited for blind decomposition by Independent Component Analysis (ICA). ICA produces signals reflecting the separate activities of the independent signal sources, plus maps giving their respective projections to the scalp surface. A stability analysis of ICA decomposition of event-related 31-channel EEG data collected during a visual selective attention task ( Makeig et al., J. Neurosci, 1999 1Mb, .pdf), plus trial analyses of higher-density EEG data, suggests that high density arrays may be most suitable for EEG-based functional imaging using ICA, but only if high quality data are recorded at a sufficient number of channels. In general, the functional independence of ICA-decomposed sources must be tested for (a) physiologically plausibility and (b) distinct and precise relationships to behavior or other variables. Decomposition of single-trial 31-channel EEG data from a visual selective attention experiment produced components meeting both criteria. Results suggest a wealth of new information about event-related brain dynamics, including: (1) A new view of the interaction between human attention and fast motor responding. (2) New hypotheses about the further decomposition of the late positive complex (or P300) into EEG-based subcomponents. (3) New information about the relation of early (P1/N1) visual response components to ongoing EEG processes.
CORTICAL LESIONS AFFECT THE LATE POSITIVE POTENTIAL
DURING VISUAL-SPATIAL ATTENTIONEdwards, E (1), Townsend, J (2), Westerfield, M (2), Makeig, S (3), Jung, TP (3)
(1) Children’s Hospital Research Center, San Diego, CA (2) UC San Diego, La Jolla, CA (3) Salk Institute, La Jolla, CA
This study assesses the contributions of different cortical regions to the Late Positive Complex (LPC). Additional data from cerebellar lesion subjects are presented in the companion poster by Westerfield et al. Event-related potentials were recorded from twelve cortical stroke patients and age-matched controls during a visual-spatial task. The results were analyzed using both traditional peak-based methods and Independent Component Analysis (ICA). The stroke patients had lesions affecting temporal, parietal and frontal cortex. Unilateral lesions of the temporal-parietal junction were found to severely reduce the LPC bilaterally. Components of the LPC were differentially affected by lesions in the frontal and parietal lobes. These results are in agreement with the results of Knight 1997 and extend those findings to components of the LPC as derived from ICA.
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