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Hernandez, Rene Suzan
Effects of task condition on the relationship of EEG coherence and full scale IQ in children.

Order No.8820228

EEG coherence (COH) is a quantitative comparison of the waveshape between spatially distinct EEG signals, and is thought to indicate the number and strength of cortical connections. Thatcher et al. (1983) found a robust negative correlation between COH during eyes-closed (EC) rest and full scale IQ in 191 children. In contrast, Orme-Johnson et al. (1982) reported a positive correlation in frontal leads between COH during practice of the Transcendental Meditation (TM) technique and verbal IQ in 47 adults. This study attempted to reconcile these findings and to further clarify the functional significance of COH by testing COH-IQ correlations across a dynamic range of brain states.

The Wechsler Intelligence Scale for Children-Revised and a test for handedness were administered to 24 female and 24 male right- handed normal children. Seventy-two seconds of EEG data were recorded from 16 monopolar leads in four frequency bands during three task conditions, EC rest, a mental arithmetic task, and TM practice. COH was computed for 10 intrahemispheric and 7 interhemispheric lead combinations. Polynomial regression analyses (BMDP 5R) of full scale IQ regressed on each of the COH variables demonstrated significant negative COH-IQ correlations in posterior scalp locations in all frequency bands in EC, and the negative correlatons held up across the three task conditions. However, a consistent trend toward positive COH-IQ correlations was found in anterior leads. Multiple analyses of covariance (BMDP 4V) found significant differences between anterior and posterior COH-IQ correlations for interhemispheric lead pairs in delta and theta frequencies in all task conditions.

The negative COH-IQ correlations in posterior leads replicated previous findings in children, and was consistent across a range of mental activation. In contrast, the significant positive frontal COH-IQ correlation suggests that the functional significance of COH may depend upon scalp location, with frontal COH being distinct from posterior regions. These findings also suggest that TM practice produces measurable changes in the functional activity of frontal areas of the brain, which was consistent with reports of greater emotional stability in TM practitioners. Source: DAI, 49, no. 08B, (1988): 3032

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