Two different motor systems are needed to generate human speech

Holstege, Gert and Subramanian, Hari H. (2016) Two different motor systems are needed to generate human speech. Journal of Comparative Neurology, 524 8: 1558-1577. doi:10.1002/cne.23898

Author Holstege, Gert
Subramanian, Hari H.
Title Two different motor systems are needed to generate human speech
Journal name Journal of Comparative Neurology   Check publisher's open access policy
ISSN 1096-9861
Publication date 2016-06-01
Year available 2015
Sub-type Critical review of research, literature review, critical commentary
DOI 10.1002/cne.23898
Open Access Status Not Open Access
Volume 524
Issue 8
Start page 1558
End page 1577
Total pages 20
Place of publication Hoboken, NJ, United States
Publisher John Wiley & Sons
Language eng
Abstract Vocalizations such as mews and cries in cats or crying and laughter in humans are examples of expression of emotions. These vocalizations are generated by the emotional motor system, in which the mesencephalic periaqueductal gray (PAG) plays a central role, as demonstrated by the fact that lesions in the PAG lead to complete mutism in cats, monkeys, as well as in humans. The PAG receives strong projections from higher limbic regions and from the anterior cingulate, insula, and orbitofrontal cortical areas. In turn, the PAG has strong access to the caudal medullary nucleus retroambiguus (NRA). The NRA is the only cell group that has direct access to the motoneurons involved in vocalization, i.e., the motoneuronal cell groups innervating soft palate, pharynx, and larynx as well as diaphragm, intercostal, abdominal, and pelvic floor muscles. Together they determine the intraabdominal, intrathoracic, and subglottic pressure, control of which is necessary for generating vocalization. Only humans can speak, because, via the lateral component of the volitional or somatic motor system, they are able to modulate vocalization into words and sentences. For this modulation they use their motor cortex, which, via its corticobulbar fibers, has direct access to the motoneurons innervating the muscles of face, mouth, tongue, larynx, and pharynx. In conclusion, humans generate speech by activating two motor systems. They generate vocalization by activating the prefrontal-PAG-NRA-motoneuronal pathway, and, at the same time, they modulate this vocalization into words and sentences by activating the corticobulbar fibers to the face, mouth, tongue, larynx, and pharynx motoneurons.
Keyword Emotional motor system
Motor cortex
Nucleus retroambiguus
Periaqueductal gray
Volitional or somatic motor system
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Published online 17 November 2015

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
Collections: Queensland Brain Institute Publications
Official 2016 Collection
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Citation counts: TR Web of Science Citation Count  Cited 8 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 6 times in Scopus Article | Citations
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