A PET study of the neural systems of stuttering


THE cause of stuttering is unknown1. Failure to develop left-hemispheric dominance for speech is a long-standing theory1 although others implicate the motor system more broadly2, often postulating hyperactivity of the right (language non-dominant) cerebral hemisphere3. As knowledge of motor circuitry has advanced4, theories of stuttering have become more anatomically specific, postulating hyperactivity of premotor cortex, either directly5 or through connectivity with the thalamus and basal ganglia6. Alternative theories target the auditory7 and speech production8,9 systems. By contrasting stuttering with fluent speech using positron emission tomography combined with chorus reading to induce fluency, we found support for each of these hypotheses. Stuttering induced widespread over-activations of the motor system in both cerebrum and cerebellum, with right cerebral dominance. Stuttered reading lacked left-lateralized activations of the auditory system, which are thought to support the self-monitoring of speech, and selectively deactivated a frontal–temporal system implicated in speech production. Induced fluency decreased or eliminated the overactivity in most motor areas, and largely reversed the auditory-system underactivations and the deactivation of the speech production system. Thus stuttering is a disorder affecting the multiple neural systems used for speaking.

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Fox, P., Ingham, R., Ingham, J. et al. A PET study of the neural systems of stuttering. Nature 382, 158–162 (1996). https://doi.org/10.1038/382158a0

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