Subcortical Contributions to Motor Speech: Phylogenetic, Developmental, Clinical

• Published in: Trends in neurosciences (Regular ed.) Vol. 40; no. 8; pp. 458 - 468
• Main Authors: Ziegler, W., Ackermann, H.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2017
• Subjects: Animals; basal ganglia; birdsong; Brain - growth & development; Brain - physiology; cerebellum development; Humans; Learning - physiology; Motor Skills - physiology; Speech - physiology; Speech Disorders - genetics; Speech Disorders - physiopathology; speech motor control; vocal learning; Vocalization, Animal - physiology; speech motor control; vocal learning; basal ganglia; cerebellum development; birdsong
• ISSN: 0166-2236; 1878-108X
• DOI: 10.1016/j.tins.2017.06.005

Vocal learning is an exclusively human trait among primates. However, songbirds demonstrate behavioral features resembling human speech learning. Two circuits have a preeminent role in this human behavior; namely, the corticostriatal and the cerebrocerebellar motor loops. While the striatal contribution can be traced back to the avian anterior forebrain pathway (AFP), the sensorimotor adaptation functions of the cerebellum appear to be human specific in acoustic communication. This review contributes to an ongoing discussion on how birdsong translates into human speech. While earlier approaches were focused on higher linguistic functions, we place the motor aspects of speaking at center stage. Genetic data are brought together with clinical and developmental evidence to outline the role of cerebrocerebellar and corticostriatal interactions in human speech. After decades of research centered on higher linguistic functions in human communication, the question of how motor mechanisms of speech are implemented in the human brain is gaining ground in neuroscience [42,72]. Recent advances in our understanding of how motor skills are acquired [7] have fertilized investigations into corticostriatal and cerebrocerebellar contributions to speech motor learning. Comparative phylogenetic approaches to speech are hampered by the fact that nonhuman primates almost completely lack the ability of vocal learning [22]. By contrast, songbirds provide a more tractable model of vocal skill acquisition, offering intriguing molecular genetic, neurophysiological, and behavioral parallels with human speech. A promising translational approach to speech motor control should integrate clinical and developmental evidence with the songbird model.