Cerebral areas associated with motor control of speech in humans

Abstract

We have defined areas in the brain activated during speaking, utilizing positron emission tomography. Six normal subjects continuously repeated the phrase "Buy Bobby a poppy" (requiring minimal language processing) in four ways: A) spoken aloud, B) mouthed silently, C) without articulation, and D) thought silently. Statistical comparison of images from conditions A with C and B with D highlighted areas associated with articulation alone, because control of breathing for speech was controlled for; we found bilateral activations in sensorimotor cortex and cerebellum with right-sided activation in the thalamus/caudate nucleus. Contrasting images from conditions A with B and C with D highlighted areas associated with the control of breathing for speech, vocalization, and hearing, because articulation was controlled for; we found bilateral activations in sensorimotor and motor cortex, close to but distinct from the activations in the preceding contrast, together with activations in thalamus, cerebellum, and supplementary motor area. In neither subtraction was there activation in Broca's area. These results emphasize the bilaterality of the cerebral control of "speaking" without language processing.

Nasal consonant production in Broca’s and Wernicke’s aphasics: Speech deficits and neuroanatomical correlates

“…These results are consistent with those of Baum et al (1990) who showed the most severe impairments in the production of voice-onset time emerging when these same areas were damaged. They are also consistent with neuroimaging results with normal subjects showing increased activation of sensorimotor and motor cortex during speech articulation (Murphy, Corfield, Guz, Fink, Wise, Harrison, and Adams, 1997;Huang, Carr, and Cao, 2001;Blank, Scott, Murphy, Warburton, and Wise, 2002).…”

Positive Emotions Preferentially Engage an Auditory–Motor “Mirror” System

“…Highly arousing emotional vocalizations therefore engage a region involved in higherorder aspects of complex motor control. Convergent valence-and arousal-related perceptual responses within the somatotopically arranged left and right lateral premotor and motor cortices (Buccino et al, 2001;Alkadhi et al, 2002) were maximal in the face motor area (Buccino et al, 2001;Carr et al, 2003;Leslie et al, 2004) but also extended into more ventral regions involved in the motor control of articulation (Murphy et al, 1997;Blank et al, 2002;Wilson et al, 2004). Lateral premotor activation was found to extend posteriorly into primary motor regions in both hemispheres.…”

Central nervous system control of the laryngeal muscles in humans

“…Using PET, one study measured brain activity levels during speech production of a repeated phrase during prolonged expiration and subtracted activity when the same subjects were mouthing the same speech phrase during tidal breathing without voice. The purpose was to identify those regions of brain activity used for voice control for speech along with prolonged expiration (Murphy et al, 1997). A complex pattern of brain activation included: high primary motor activity probably for diaphragm and chest wall control (labeled "mc"); auditory region in the superior temporal lobe activation (tc); and a region labeled "smc2" which the authors denoted as activated for voice and breathing (Fig.…”

“…This area was closer to the primary motor region for the lips and jaw for movements for speech articulation and did not involve the laryngeal motor cortex closer to the sylvian fissure (Simonyan and Jurgens, 2003). In addition, there was a symmetric pattern of activation in the two hemispheres and no activation in Broca's area (Murphy et al, 1997). The use of subtraction methods to identify behavioral components in tasks, however, makes assumptions about additivity that have been widely questioned (Sidtis et al, 1999).…”

“…The areas of activation for swallowing are more extensive (Fig. 5C), than those active for volitional breathing control (Ramsay et al, 1993;Evans et al, 1999;McKay et al, 2003), or for vocalization with prolonged expiration during speech (Murphy et al, 1997;Huang et al, 2002). This may be because several functions are involved, such as the taste sensation from the bolus, jaw and tongue movement associated with moving the bolus to the oropharynx, and eliciting the reflexive pharyngeal swallow.…”