Thursday, October 26, 2006

Mental time keeping and human speech

Earlier today I made an FYI post (with link to article) dealing with the role of the timing function of the auditory brainstem in speech. This reminded me of an article in a recent special issue of Cognitive Brain Research that reviewed recent neuroscience research (lesion and neuroimaging) that investigated the role of timing in human speech.
  • Schirmer, A (2004). Timing speech: a review of lesion and neuroimaging findings. Cognitive Brain Research, 21, 269–287 (click to view)
What I find particularly interesting is the spotlight (in this review article) on the basal ganglia, cerebullum and the left frontal cortex in speech-related timing behavior. Why?

Because the preponderance of mental interval time-keeping research consistently is pointing to the "master internal brain clock" being localized in the same general areas; particularly the basal ganglia, cerebullum, dorsolateral prefrontal cortex, and the frontial-striatal loop (Buhusi & Meck; 2005; Janata & Grafton, 2003; Nobre & O’Reilly, 2004; Peretz & Zatorre, 2005). Schimer concludes that the "BG [basal ganglia] and the cerebellum might perform more general timing operations that feed into other cognitive processes such as the processes specific to speech." In other words, Shimer is arguing for a domain-general, brain-based, mental time-keeper that functions in synchrony with possible domain-specific cognitive mechanisms specific to speech behavior.

  • Time is a fundamental dimension of behavior and as such underlies the perception and production of speech. This paper reviews patient and neuroimaging studies that investigated brain structures that support temporal aspects of speech. The left-frontal cortex, the basal ganglia, and the cerebellum represent structures that have been implicated repeatedly. A comparison with the structures involved in the timing of nonspeech events (e.g., tones, lights, finger movements) suggests both commonalities and differences: while the basal ganglia and the cerebellum contribute to the timing of speech and non-speech events, the contribution of left-frontal cortex seems to be specific to speech or rapidly changing acoustic information. Motivated by these commonalities and differences, this paper presents assumptions about the function of basal ganglia, cerebellum, and cortex in the timing of speech.
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