PET Portrays Pictures of the Brain During Vocalization

Background: Voice is an essential function needed for spoken language and in itself transmits important information – about emotional state, intentionality, and arousal – that significantly enriches human communication. Until recently, neuroimaging methods had not been used to evaluate how the brain produces and regulates vocalization – how it organizes and monitors vocalization in the course of speech production. Understanding brain mechanisms that support this process is important because impaired vocalization is a part of a host of human communication disorders.

Credit: NIH

Advance: Using positron emission tomography (PET), NIDCD intramural scientists have discovered that during phonation, humans activate the older portions of the brain. This same system is used by a wide variety of lower animals when they produce species-specific vocalizations (alarm or mating calls, for example). What makes humans different is that this system appears to have come under voluntary control of more recently evolved regions of the brain. These latter regions are coactivated and strongly coupled with activity in the older regions when humans vocalize. In addition, there are marked differences in the brain regions that humans use in hearing their own voice during speaking as opposed to hearing the voice of others. Moreover, robust functional connections between the hearing and speech systems appear when the brain monitors and corrects speech.

Implications: Identifying and characterizing the human vocalization system at the functional level provides intriguing insights into the evolution of vocal control. Older brain mechanisms NIDCD-21 appear to have been recruited and placed under voluntary control during the evolution of speech. Breakdown of these control processes may be important in the understanding disorders characterized by an inability to voluntarily regulate voice and speech, for example, stuttering, spasmodic dysphonia, Tourette’s syndrome, and post-stroke dyspraxia. Brain imaging methods may provide a way of evaluating treatments aimed at ameliorating these disorders.

Citation: Schulz GM, Varga M, Jeffires K, Ludlow CL, Braun AR. Functional Neuroanatomy of Human Vocalization: An H215O PET Study. Cereb Cortex EPub doi:10.1093/cercor/bhi061, 2005.

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