Analysis of the effects of motor command for vocalization upon auditory mechanisms in the brainstem

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To investigate the effects of motor commands for vocalization upon auditory mechanisms in the brainstem during actual vocalization movement, we first identified the auditory relay neurons within the brainstem, and analyzed the inputs from the vocalization center and their discharge properties.In precollicular-postmammilary decerebrate cats, we employed the midbrain periaqueductal gray as the vocalization center, and analyzed the discharge properties of auditory relay neurons within the dorsal and ventral nuclei of the lateral remuniscus responding to the auditory stimuli that has the same fundamental frequency and formant as those of induced vocalization. These stimuli were reconstructed by the computer controlled apparatus that was equipped by this grant.We first tried to identify the responsibility to the single electrical shock delivered to the vocalization center and the responsibility to the different auditory stimuli, and then the discharge properties of these neurons during the actual vocalization movements.Most of recorded auditory relay neurons did not respond to the single shock delivered to the vocalization center within the stimulus strength which could induce vocalization movements. With higher stimulus strength, some neurons received suppressive effects and some were excitatory. However, these differences were not significant statistically, so that we did not published our results yet. To clarify the effects from the vocalization center, we are now trying to analyze the effects upon the discharges induced by the auditory stimuli. The analysis of discharge properties of auditory relay neurons during actual vocalization was not performed yet, because accompanying movements of brainstem was unexpectedly large so that stable recording was quite difficult.