Midbrain regions for eliciting vocalization by electrical stimulation in anesthetized dogs

Eliciting vocalization in anesthetized dogs by midbrain stimulation is a useful procedure for studies of laryngeal and respiratory physiology. The goal of this report has been to construct a canine stereotaxic "map" that would allow investigators to locate midbrain stimulus sites producing vocalization. Motor responses to electrical stimulation at currents of 1.5 mA or less were observed at 1,158 stimulus sites throughout the midbrains of 8 dogs. Vocalization was observed at 213 stimulus sites. The highest probability of observing vocalization was for sites located 6 to 10 mm anterior, 6 to 7 mm lateral, and 5 to 8 mm dorsal to earbar zero. The vocalization region most likely consists of axons arising in the midbrain periaqueductal gray and coursing through the adjacent tegmentum; low-threshold sites are close to the medial lemniscus. The relationship between stimulus sites at which vocalization was elicited and sites producing other motor responses is described.