A positron emission tomography study of silent and oral single word reading in stuttering and nonstuttering adults

Over the last decade positron emission tomography (PET) has been used exten sively for the study of language and other cognitive and sensorimotor proce sses in healthy and diseased individuals. In the present study [O-15]H2O PE T scanning was used to investigate the lateralization and functional distri bution of cortical and subcortical activity involved in single word reading in stuttering and nonstuttering individuals. Ten right-handed male stutter ing adults and marched nonstuttering individuals were instructed to read in dividually presented single words either silently or out loud. Subtraction of Functional brain images obtained during each of the two reading tasks, a nd during a non-linguistic baseline task, was used to calculate within-grou p and between-group differences in regional cerebral blood flow by means of statistical parametric mapping. Increased activation in the left anterior cingulate cortex (ACC) was observed during silent reading in the stuttering speakers but not in the nonstuttering group. Because of the hypothesized r ole of the ACC in selective attention and covert articulatory practice, it is suggested that the observed increased ACC activation in the stuttering i ndividuals reflects the presence of cognitive anticipatory reactions relate d to stuttering. During the oral reading task, within-group comparisons sho wed bilateral cortical and subcortical activation in both the stuttering an d the nonstuttering speakers. Between-group comparisons showed a proportion ally greater left hemisphere activation in the nonstuttering speakers, and a proportionally greater right hemisphere activation in the stuttering indi viduals. The results of the present study provide qualified support for the hypothesis that stuttering adults show atypical lateralization of language processes.