A comparative study on the elicitability of vocalization by electrical brain stimulation, glutamate, aspartate and quisqualate in the squirrel monkey.

In 6 squirrel monkeys (Saimiri sciureus), 71 brain sites yielding vocalization when electrically stimulated were tested for their capability to produce vocalization when injected with L-glutamate (Glu), N-methyl-D-aspartate (NMDA) and quisqualate. Out of the 71 sites, only 3 reacted positively to Glu, 4 to quisqualate and 7 to NMDA. Two of the quisqualate-positive sites reacted also to NMDA and one to Glu. The positive sites were located at the border between the substantia innominata and globus pallidus, in the periaqueductal gray of the midbrain, and in the lateral reticular formation of midbrain, pons and medulla. These areas are interpreted as relay stations within a more widespread vocalization-control system.