Cerebral Cortex Advance Access originally published online on January 31, 2008
Cerebral Cortex 2008 18(8):1923-1932; doi:10.1093/cercor/bhm220
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Common Neural Substrates for Inhibition of Spoken and Manual Responses
1 FPR-UCLA Center for Culture, Brain and Development, University of California, Los Angeles, CA 90095, USA, 2 Department of Psychology, University of California, Los Angeles, CA 90095, USA, 3 Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA 90095, USA, 4 Brain Research Institute, University of California, Los Angeles, CA 90095, USA, 5 Current address: Department of Psychology, University of Southern California, Los Angeles, CA 90089, USA, 6 Current address: Department of Psychology, University of California, San Diego, CA 92093, USA
Address correspondence to Russell A. Poldrack, Department of Psychology, University of California, Los Angeles, Franz Hall, Box 951563, Los Angeles, CA 90095-1563, USA. Email: poldrack{at}ucla.edu.
The inhibition of speech acts is a critical aspect of human executive control over thought and action, but its neural underpinnings are poorly understood. Using functional magnetic resonance imaging and the stop-signal paradigm, we examined the neural correlates of speech control in comparison to manual motor control. Initiation of a verbal response activated left inferior frontal cortex (IFC: Broca's area). Successful inhibition of speech (naming of letters or pseudowords) engaged a region of right IFC (including pars opercularis and anterior insular cortex) as well as presupplementary motor area (pre-SMA); these regions were also activated by successful inhibition of a hand response (i.e., a button press). Moreover, the speed with which subjects inhibited their responses, stop-signal reaction time, was significantly correlated between speech and manual inhibition tasks. These findings suggest a functional dissociation of left and right IFC in initiating versus inhibiting vocal responses, and that manual responses and speech acts share a common inhibitory mechanism localized in the right IFC and pre-SMA.
Key Words: fMRI • language • response inhibition • right IFC • stop signal