Neural Coding Primate Vocalizations in Auditory Cortex

Johns Hopkins University, Baltimore MD

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Abstract

[unreadable] DESCRIPTION (provided by applicant): The goal of this thesis proposal is to investigate the neural coding of species-specific communication sounds in the common marmoset (callithrix jacchus jacchus) using statistically accurate synthetic vocalizations. These virtual vocalizations are defined almost entirely in terms of a set of acoustical parameters which have been measured from hundreds of actual vocalizations recorded from animals in our colony. These parameters can be systematically manipulated in order to determine precisely which acoustical properties of the vocalization are important for vocalization selective responses in the auditory cortex. These stimuli represent a tremendous improvement over the single vocalization token stimuli which have been employed in studies of cortical vocalization encoding. One issue which we hope to address is what role harmonic and temporal combination sensitivity plays in shaping responses to vocalizations, as these mechanisms have been found to be important for vocalization selectivity in the songbird and echolocating bat. Another issue which we are interested in investigating is the relative importance of spectral and envelope information in vocalization processing. The virtual vocalization stimuli allow us to manipulate the frequency and amplitude information in the call independently so that this question can be rigorously addressed. Lastly we are interested in recording from multiple regions of the auditory cortex, in particular the lateral belt fields AL and CL, in order to critically test the recently proposed theory that the AL field exhibits a higher degree of vocalization selectivity than CL.