EEG alpha asymmetries in stutterers and non-stutterers: effects of linguistic variables on hemispheric processing and fluency.

The EEG hemispheric alpha asymmetry technique was used to gather data from anterior and posterior language areas during a resting condition and in a sentence repetition task. Subjects were nine adult stuttering males and nine adult fluent male controls. Sentences were controlled for imagery, syntactic complexity, and rate. Significant within- and between-groups differences were found for both resting and testing conditions. Posteriorly, stutterers showed no differences between resting and testing conditions, while controls showed increased left hemisphere activation. Of the linguistic variables investigated, only imagery was involved in a significant interaction. Fluent males showed greater posterior left hemispheric activation for high and low visual imagery sentences, compared to greater posterior right hemispheric activation in stuttering males. Significantly greater alpha power was found for low vs high imagery sentences in the anterior and posterior left hemisphere sites for both subject groups, and in the right hemisphere sites for the stuttering group only. Fluency data is presented. Differences between groups in alpha power changes from resting to testing conditions are discussed.