The Role of Subcortical Regions in Speech Production

ABSTRACT

BACKGROUND: Speech production requires accurate coordination of the speech musculature, and is dependent upon cooperation among cortical and subcortical structures. Multiple subcortical structures, including the basal ganglia, thalamus, and cerebellum, are involved in several parallel and segregated cortical-subcortical-cerebellum circuits. These circuits serve critical functions in integrating neural networks that modulate speech motor behaviors. Previous studies on speech disorders linked to subcortical lesions have been limited to perceptual evaluations of speech in patients with lesions. However, more recent studies using neuroimaging have confirmed the results of the lesion studies and provided further evidence of the important contributions of the subcortical structures to speech motor control. METHODS: We reviewed recent research literature on both behavioral and functional neuroimaging to reveal the role of subcortical structures in speech production. A review of this topic was conducted by searching the literature and electronic databases. RESULTS: Based on numerous articles, we found that the basal ganglia, thalamus, and cerebellum make different contributions to the modulation of speech-related variables. The cerebellum is the structure that is most strongly associated with speech rate, complexity, and timing. CONCLUSIONS: We conclude that the subcortical structures may play critical functions in speech production. The function of each structure involves the stimulation of cortical regions through the neural circuits and neurotransmitters. Thus, the function of the subcortical structures should be understood within the paradigm of neural networks.