Perceptual Factors in Workload: A Neuromagnetic Study.
Annual technical rept. 1 Jan-31 Dec 86,
NEW YORK UNIV N Y
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This annual report describes the five channel neuromagnetometer operating at NYU, and the principles underlying its use. If further describes recent advances in methodology, including the results of a theoretical study showing that measurement of the field at least five different positions is needed to fully characterize a single dipole source. The number of recording positions increases markedly with noise. Therefore, a shielded environment would minimize the number of recording sessions required for a neuromagnetic study. The report also provides a history of the work in relevant areas, and goes on to describe a completed study of selective auditory attention. It was found that magnetic counterparts of N100 and P200 of the event related potential show a strong effect of attention in a dichotic listening task. The magnetic components N100m and P200m can be accounted for by sources located in the auditory cortex, and do not change in position or depth with attention. The effect of attention is to change the tangential current dipole moment. Analysis of variance ANOVA using the field messurements near field extrema show that the only effect of significance is that of the instruction to attend or not to attend to the stimulus. This result is reflected in the change in source intensity dipole moment. The results are consistent with an early filter theory of attention, and seem to be inconsistent with the analysis by synthesis approach. Moreover, the results suggests that the filtering operations associated with selective attention occur in the primary sensory projection areas, although roles for other areas cannot be completely ruled out.
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