Chapter 19 Midbrain and medullary regulation of respiration and vocalization

Abstract

There is evidence that the respiratory changes and vocalization associated with emotional behaviors are dependent on an intact midbrain specifically the lateral part of the caudal two-thirds of the periaqueductal gray matter (PAG) surrounding the aqueduct The lateral column of the midbrain periaqueductal gray (PAG) appears to contain the motor pattern generators for various types of vocalization. Further, the motor patterns that can be evoked by PAG neuronal excitation are influenced by afferent control mechanisms linked to the availability of air in the lungs. The PAG has been shown to influence the excitability of laryngeal adductor (thyroarytenoid), tensor (crico-thyroid), and expiratory (internal intercostal, external oblique, internal oblique) muscles indirectly, via the nucleus retroambigualis (NRA) while the PAG control of oro-facial muscles involves a separate pathway that does not appear to include a synapse in the NRA. Neurons in the lateral PAG column could play an important role, not only in the production of emotional vocalization, but also as a generator of specific respiratory and laryngeal motor patterns essential for human speech and song.