11 1. Physiological Foundations of Speech (Material to Dysarthria) ¿De dónde eres? [where are you from?] All in all, intonation understood as changing the voice’s pitch involves rising, falling, or fluctuating the pitch within an utterance. It helps differentiate between interrogative, declarative, or imperative utterances or exclamations in a way characteristic of each language. Let us now sum up the role of the speech organs in speech motor production by noting that different sets of organs are responsible for different aspects of speech. The articulatory organs fulfill fundamental functions in speech production: the tongue movement and its position are responsible for producing specific speech sounds (segments). The lip muscle tension influences the quality of bilabial (p, b, m) and labiodental consonants (v and f); the degree of mouth opening, lip rounding, and jaw and tongue positioning (more precisely the muscles of mastication) affect the quality of vowels. The oral/nasal parameter depends on the soft palate, with the uvula closing or opening the passage between the nasopharynx, the nasal cavity, and the oral cavity, which modifies the airstream pathway and selects the resonator. Phonation, in turn, depends on the vocal folds, larynx, and the movement and contraction of the respiratory muscles. Additionally, prosodic elements such as stress and intonation highlight prominent units within a sentence and help recognize its illocutionary force, respectively. 1.4. THE ROLE OF THE BRAIN AND CEREBELLUM IN EXECUTIVE ASPECTS OF SPEECH PRODUCTION The motor activity of the speech organs is initiated and controlled in the motor cortex in both brain hemispheres, specifically in the precentral gyrus and paracentral lobule near the lateral fissure. These cortical locations, corresponding to the facial muscles, lower jaw, tongue, pharynx and larynx, have to be coordinated in volitional voice production. The motor fibers from the relevant cortical locations run through the corticobulbar tract (including both decussating and non-decussating fibers) to the motor nuclei of cranial nerves of the medulla oblongata (nerves IX, X, XII) and the pons (nerves V and VII). Motor fibers leaving these nuclei innervate the skeletal muscles of the articulatory organs. In addition to the neural structures mentioned above, speech production also engages the cerebellum and basal nuclei.
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