Neural Representation of Vocalizations in the Primate Ventrolateral Prefrontal Cortex

1 Departments of Neurobiology and Anatomy and 2 Brain and Cognitive Sciences, University of Rochester, Rochester, New York Submitted 2 July 2004; accepted in final form 9 September 2004 In this study, we examined the role of the ventrolateral prefrontal cortex in encoding communication stimuli. Specifically, we recorded single-unit responses from the ventrolateral prefrontal cortext (vlPFC) in awake behaving rhesus macaques in response to species-specific vocalizations. We determined the selectivity of vlPFC cells for 10 types of rhesus vocalizations and also asked what types of vocalizations cluster together in the neuronal response. The data from the present study demonstrate that vlPFC auditory neurons respond to a variety of species-specific vocalizations from a previously characterized library. Most vlPFC neurons responded to two to five vocalizations, while a small percentage of cells responded either selectively to a particular vocalization type or nonselectively to most auditory stimuli tested. Use of information theoretic approaches to examine vocalization tuning indicates that on average, vlPFC neurons encode information about one or two vocalizations. Further analysis of the types of vocalizations that vlPFC cells typically respond to using hierarchical cluster analysis suggests that the responses of vlPFC cells to multiple vocalizations is not based strictly on the call's function or meaning but may be due to other features including acoustic morphology. These data are consistent with a role for the primate vlPFC in assessing distinctive acoustic features. Address for reprint requests and other correspondence: L. M. Romanski, University of Rochester Medical Center, Dept. of Neurobiology and Anatomy, Box 603, 601 Elmwood Ave, Rochester, NY 14642 (E-mail: liz_romanski{at}urmc.rochester.edu )