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Maharishi Vedic Science


Sheppard II, William DeLime
Pretrial EEG coherence as a predictor of semantic processing effects in a lexical decision task

Order No. 8820229

Twenty-four subjects were each presented 240 randomized trials of a lexical decision task (LDT) while connected to a 16-electrode EEG montage. EEG data were acquired for two seconds prior to the onset of each LDT trial. The LDT trial consisted of a fixation asterisk, a prime letter string, a pattern mask, and a target letter string. Following the lexical decision, the subject gave a verbal report identifying the prime as word or neutral and a number estimate of the confidence of that report. EEG alpha coherence, alpha power, and 3-30 Hz wide- band power from five different combinations of EEG electrodes were used to predict semantic effects in the LDT trials. Results showed significantly different relationships between coherence and semantic effects depending upon prime duration and prime- target relatedness. High pretrial coherence in the right hemisphere was correlated with greater processing efficiency in slow, related-prime trials. High pretrial coherence in the left hemisphere was correlated with greater prime identification accuracy in slow-prime trials; although for fast-prime trials, interhemispheric coherence was inversely correlated with prime identification accuracy. A model of the relationship between coherence and neural information processing is discussed. Source: DAI, 49, no. 09B, (1988): 3610


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