Localization of a pontine vocalization-controlling area

To find out whether there exist additional regions in the pontine brainstem , apart from the phonatory motoneuron pools involved in vocal motor control , the effects of a localized blockade of excitatory neurotransmission in th e pons were studied on squirrel monkey vocalization. Vocalization was elici ted by electrical stimulation of the periaqueductal gray of the midbrain. B lockade was carried out by stereotaxic injections of kynurenic acid, a nons pecific glutamate antagonist. It was found that injections made into the ve ntrolateral pens around the ventral nucleus of the lateral lemniscus and su perior olive could block periaqueductally elicited vocalization. Injections were only effective ipsilaterally, not contralaterally to the stimulation site. The blockade was limited to one particular class of calls, all of whi ch had in common a characteristic stereotyped frequency modulation over sev eral kHz. It is concluded that critical processing steps of vocal motor con trol take place in the periolivary region. (C) 2000 Acoustical Society of A merica. [S0001-4966(00)00110-7].