Preliminary results of a functional MRI study of brain activation patterns in stuttering and nonstuttering speakers during a lexical access task

Abstract

An fMRI study examining lexical access and lexical generation in nine nonstuttering and seven stuttering speakers is presented. Lexical access was examined during a word description task that was presented auditorily while subjects “silently” thought of the target words. Participants alternated between four 30-s rest blocks and four 30-s “active” blocks. Activation patterns were assessed utilizing a standard subtraction paradigm, where the activation during the rest blocks was subtracted from the activation during the active blocks. High levels of variability characterized activation patterns within both speaker groups. Group comparisons using random effects statistical analyses did not identify significant differences between the groups when corrected for multiple comparisons. Analyses were subsequently conducted by comparing the trends in the group activation patterns between the speaker groups using fixed (corrected) and random effects (uncorrected) analyses. Nonstuttering control speakers activated primarily left hemisphere cortical speech and language areas while the stuttering speakers appeared to produce more bilateral activation. Discussion of these results focuses on the specific within- and between-hemispheric activation patterns and possible interpretations of these patterns. Educational objectives: The reader will learn about: (1) issues related to interpreting brain activation findings in stuttering speakers; (2) the role and neurological substrates of lexical access during speech production in nonstuttering and stuttering speakers; (3) the basics of functional MRI; and (4) the brain activation areas involved during a silent lexical retrieval task in nonstuttering and stuttering speakers.