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Abstract:
The design of the primate auditory system should reflect the specialized functions that it evolved to carry out. One such function is conspecific vocal recognition. Measuring the neural selectivity to vocalizations is a way to identify the mechanisms underlying this auditory specialization. Previous studies examining call selectivity in the primate auditory cortex suffered from two drawbacks: an impoverished stimulus set and/or the use of anesthetized or passive-listening paradigms. We adopted a simple behavioural task to study how neurons in the rhesus monkey auditory cortex respond to conspecific vocalizations. Two monkeys were trained to listen to sound sequences composed of one or two conspecific vocalizations (mean SPL=79.9 dB) and an artificial horn sound (frequency bandwidth: 788Hz-11kHz; 300ms in duration; SPL=69.7 dB) presented in free-field. They were rewarded if they pulled a lever within 1 sec following the horn sound. Both monkeys were able to do this task at >95-correct performance levels. This task requires that the monkey attend in the auditory domain without the confounds of over-training on vocalizations and the response lability that occurs during passive-listening. Our stimuli consist of 3 exemplars from each of 7 call categories (coos, pant-threats, grunts, aggressive barks, shrill barks, noisy screams and harmonic arches). Using this paradigm, we are investigating whether the responses of auditory ‘belt’ cortical neurons reflect category-level selectivity to conspecific vocalizations.
