Abstract

Introduction

The somatic motor system

The emotional motor system (EMS)

Speech as the product of somatic and emotional motor systems

References

Discussion
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The final motor output necessary for the production of vocalization in mammals is organized in the caudal periaqueductal gray (PAG). This midbrain region receives strong input from many different sites in the limbic system, in several of which vocalization can be elicited. Bilateral lesions in the caudal PAG produce completely mute animals. It has been shown that the distinct PAG projection to the nucleus retroambiguus (NRA) in the caudal medulla subserves vocalization. The NRA, in turn, projects to abdominal muscle motoneurons, necessary for increasing the abdominal pressure, and to motoneurons in the nucleus ambiguus innervating soft palate, pharynx and larynx. Moreover, partial lesions of the NRA produce important deviations in the vocalization of cats, while bilateral complete lesions result in total muteness. It will be argued that in humans vocalization is an essential part of the production of speech, although the capability to modulate vocalization into specific words and sentences is a cortical function. It will be pointed out that the PAG is the final organizer of survival behavior in general, and plays a crucial role in the emotional motor system (EMS). The PAG not only organizes vocalization, but also nociception, blood pressure, micturition, copulation, and basic level setting systems.

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Presentation Number SAholstege0261
Keywords: periaqueductal, retroambiguus, emotional, larynx, abdominal