Neuronal activity in the medulla oblongata during vocalization. A single-unit recording study in the squirrel monkey

Area of Science:

• Neuroscience
• Primatology
• Bioacoustics

Background:

• The neural mechanisms underlying vocalization are complex and not fully understood.
• Identifying specific brain regions involved in vocal control is crucial for understanding communication in primates.

Purpose of the Study:

• To investigate vocalization-correlated neuronal activity in the medulla oblongata of squirrel monkeys.
• To map the distribution and characteristics of vocalization-related cells within different brain structures.

Main Methods:

• Microelectrode exploration of the medulla oblongata in six squirrel monkeys (Saimiri sciureus).
• Vocalizations were elicited using microinjections of glutamate agonists into the periaqueductal grey.
• Neuronal responses were categorized into 12 reaction types to differentiate vocalization-related areas.

Main Results:

• Vocalization-related cells were predominantly found in the nucleus ambiguus (Ab), retroambiguus nucleus (RAb), reticular formation (parvocellular, magnocellular, central), solitary tract nucleus, and spinal trigeminal nucleus.
• Smaller populations of vocalization-related cells were observed in the vestibular complex, cuneate nuclei, inferior olive, and lateral reticular nucleus.
• Distinct patterns of neuronal responses across brain structures allowed for the specification of different vocalization-related areas.

Conclusions:

• The parvocellular reticular formation is proposed as a key area for vocalization initiation.
• Vocal pattern control involves the parvocellular reticular formation, nucleus ambiguus, solitary tract nucleus, and spinal trigeminal nucleus.
• The retroambiguus nucleus, nucleus ambiguus, and central reticular formation are implicated in expiratory control and respiratory-laryngeal coordination, while vestibular and cuneate nuclei contribute to postural adjustments.