C-FOS EXPRESSION DURING VOCAL MOBBING IN THE NEW-WORLD MONKEY SAGUINUS-FUSCICOLLIS

In order to find brain areas involved in the vocal expression of emoti on, we compared c-fos expression in three groups of saddle-back tamari ns (Saguinus fuscicollis). One group, consisting of three animals, was made to utter more than 800 mobbing calls by electrical stimulation o f the periaqueductal grey of the midbrain (FAG). A second group, consi sting of two animals, was stimulated in the FAG with the same intensit y and for the same duration as the first group but at sites that did n ot produce vocalization. These sites lay somewhat medial to the vocali zation-eliciting sites. A third group, consisting of two animals, was stimulated at vocalization-eliciting sites in the FAG but with an inte nsity below vocalization threshold. Fos-like immunoreactivity that was found in the vocalizing but not in the non-vocalizing animals was loc ated in the dorsomedial and ventrolateral prefrontal cortex, anterior cingulate cortex, ventrolateral premotor cortex, sensorimotor face cor tex, insula, inferior parietal cortex, superior temporal cortex, claus trum, entorhinal and parahippocampal cortex, basal amygdaloid nucleus, anterior and dorsomedial hypothalamus, nucleus reuniens, lateral habe nula, Edinger-Westphal nucleus, ventral and dorsolateral midbrain tegm entum, nucleus cuneiformis, sagulum, pedunculopontine and laterodorsal tegmental nuclei, ventral raphe, periambigual reticular formation and solitary tract nucleus. For some of these structures (e.g. anterior c ingulate cortex and periambigual reticular formation), there is eviden ce also from electrical stimulation, lesioning and single-unit recordi ng studies that they are involved in vocal control. For other structur es (e.g. lateral habenula, Edinger-Westphal nucleus), the available ev idence speaks against such a role. Fos activation in these cases is pr obably related to non-vocal reactions accompanying the electrically el icited vocalizations. A third group of structures consists of areas fo r which a role in vocal control cannot be excluded but for which the p resent study presents the first evidence for such a role (e.g. claustr um and sagulum). These structures deserve further studies using more s pecific methods.