Periaqueductal gray neuronal activity associated with laryngeal EMG and vocalization in the awake monkey.

Extracellular recordings were made from 73 periaqueductal gray (PAG) neurons in an awake, vocalizing monkey (Macaca fascicularis). About 50% of the neurons were inactive and only began discharging prior to laryngeal EMG activity and vocalization; they reached their peak firing rate near the onset of vocalization and then became inactive again. Spike-triggered averaging of laryngeal EMG from the PAG unit discharge revealed in most cases an increase in laryngeal EMG immediately following the unit spike. Other cells appeared to be related to other oral-facial behaviors. The role of the PAG in vocalization is discussed.