Work in my lab is focused on understanding how the prefrontal cortex encodes complex auditory and visual object information.  The integration of auditory and visual stimuli is essential for recognizing objects, communicating effectively, and navigating through our complex world. Although it is not certain where in the brain information from these two modalities are combined and processed to govern specific behaviors, the frontal lobes have been identified as a region associated with memory and language, which depend on the integration of sensory information from multiple modalities. In previous studies we identified the sensory pathways that provide the frontal lobes with acoustic information using anatomical and physiological (Nature Neuroscience, 1999, 12, 1131-1136) techniques. The results of our studies reveal a dorsal-ventral topography in prefrontal-temporal connections that is similar to the dorsal and ventral streams of the visual system, suggesting that auditory information might follow similar “what” and “where” pathways. With the help of these anatomical results, we were able to determine that there exists, in the non-human primate, a discrete locus for the processing of complex acoustic stimuli in the ventrolateral prefrontal cortex (VLPFC).  This study provided the first evidence of an auditory processing domain in the non-human primate frontal lobe (Nature Neuroscience, 2002, 5: 15-16). We have continued our electrophysiological exploration of the primate ventrolateral frontal lobe and the first series of studies indicates that frontal lobe neurons, which respond to monkey communication calls, are activated by other auditory stimuli that are acoustically similar (Romanski et al., J. Neurophysiology, 2005).  Thus prefrontal auditory neurons may encode acoustic features and do not necessarily encode the semantic meaning of communication sounds.  Our recent work tests the hypothesis that some cells in the ventral prefrontalcortex are, in fact, multimodal.  In single unit recordings of awake monkeys we have determined that single cells in vlPFC respond to face and vocalization stimuli (Sugihara et al., submitted). Multimodal neurons that were responsive to both face and vocalization stimuli showed either a significant increase or decrease during combined stimulus presentation compared to unimodal stimulus presentation.  The multimodal neurons were most commonly found in the region between the unimodal auditory and visual vlPFC domains.  Further analysis of sensory integrated processes in the frontal lobes of non-human primates may help us to understand object recognition and speech perception in the human brain, which critically depends on the integration of multiple types of sensory information.

Romanski, L.M.,  Averbeck B.B., Diltz M. (2005) Neural Representation of Vocalizations in the Primate Ventrolateral Prefrontal Cortex.  J Neurophysiol. 93:734-47.

Romanski, L. M. (2004) Domain Specificity in the Primate Prefrontal Cortex.  Cognitive, Affective, & Behavioral Neuroscience 4: 421-429.

Romanski, L.M., and Goldman-Rakic, P.S. 2002 (online 2001), An Auditory Domain in Primate Prefrontal Cortex, Nature Neuroscience,5: 15-16.

Romanski, L.M., Tian, B., Fritz, J., Mishkin, M., Goldman-Rakic, P.S., Rauschecker, J.P. 2000, What, Where and How in Auditory Cortex, Nature Neuroscience:966.

Romanski, L.M., and Goldman-Rakic. P.S. 1999,Physiological identification of an auditory domain in the prefrontal cortex of the awake behaving monkey. SocNeurosci.Abstr. Vol. 24.

Romanski, L.M., Tian, B., Fritz, J., Mishkin, M., Goldman-Rakic, P.S., Rauschecker, J.P. 1999, Dual streams of auditory afferents target multiple domains in the primate prefrontal cortex, Nature Neuroscience, 12, 1131-1136.

Romanski, L.M., Bates, J.F. and Goldman-Rakic, P.S. 1999, Auditory belt and parabelt projections to the prefrontal cortex in the rhesus macaque, J. Comparative Neurology, 403:141-157.

Romanski, L.M., and Goldman-Rakic, P.S. 1998,View invariant responses in the inferior convexity of the prefrontal cortex of the rhesus monkey, Soc. Neurosci. Abstr., Vol. 23.

Romanski, L.M., Giguere, M., Bates, J.F. and Goldman-Rakic, P.S. 1997, Topographic organization of medial pulvinar connections with the prefrontal cortex in the rhesus monkey, J. Comparative Neurology, 379: 313-332.