The Relationship Between N2 and N400: Scalp Distribution, Stimulus Probability, and Task Relevance

Authors


  • This research was supported by grants HD10804, MH06823, and HD01799 from the USPHS, an NSERC postdoctoral fellowship to the first author, and a grant from the Fyssen Foundation to the second author. The third author is also at Lehman College, City University of New York.

Address requests for reprints to: Diana Deacon, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Kennedy 817, Bronx, New York 10461.

ABSTRACT

The N2 and N400 components of the event-related brain potential were compared along several dimensions. In one task, subjects discriminated on the basis of size, and in another task, subjects discriminated on the basis of semantic category. In one set of conditions stimuli deviated infrequently along one stimulus dimension (either in size or semantic category) and in another set of conditions stimuli deviated infrequently along two stimulus dimensions (both size and semantic category). When subjects discriminated on the basis of size, infrequent deviation in the size of the stimuli was associated with a negativity that peaked around 320 ms (N2). When subjects discriminated on the basis of semantic category, infrequent deviation in the semantic category of the stimuli was associated with a negativity that peaked around 400 ms (N400). N2 and N400 were found to be generally alike in scalp distribution, hemispheric asymmetry, and sensitivity to stimulus probability. N2 was not elicited when size changes were task irrelevant and N400 was not elicited when changes in semantic category were task irrelevant.

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