Representation of non-auditory events in monkey auditory cortex

Michael Brosch, Institute of Neurobiology, Magdeburg

Abstract
Early auditory cortex is generally considered to be unimodal. Here we describe extensive cross-modal activation in the auditory cortex of two monkeys while they performed an auditory categorization task: monkeys were required to grasp a touch bar and hold it after a cue-light was turned on. This triggered a sequence of tones of variable frequencies. Monkeys had to indicate the occurrence of a falling frequency step in the sequence by releasing the touch bar. In primary auditory cortex and posterior belt areas we found neurons whose firing was transiently synchronized to the cue-light or to the touch or release of the bar. Such firing not seen or was modified when the monkeys did not initiate a trial after the cue-light was lit or when they performed a visual task. We speculate that the responses to non-auditory events were formed by the tight association between the auditory task and visual stimuli, hand movements, and tactile feedback about the proper placement of the hand on a touch bar during the long training period (> 100,000 trials) of the monkeys. The representation of non-auditory sensory modalities and movements in auditory cortex could accelerate and improve performance of subjects in highly demanding auditory tasks.

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