TEMPORAL DYNAMICS OF CENTRAL AUDITORY PROCESSING

描述（由申请人提供）：本研究计划的总体目标是研究序列中时间离散声音之间的时间间隔如何影响中枢听觉神经元的基本反应特性。在序列中产生的声音对于大多数生物声学信号是常见的，例如蝙蝠使用的生物声纳声音和包括语音在内的通信声音。最近的研究表明，在下丘（IC）的蝙蝠神经元的幅度选择性的声音序列时，声刺激率的增加进行性增加。初步研究表明，刺激的速率对IC单元在多个维度上的响应具有更全面的影响，包括单元的频率选择性。此外，在心理物理学实验中，人类听者辨别声音水平的微小差异的能力随着声学刺激速率的增加而提高。因此，了解幅度和频率选择性的速率依赖性变化的机制不仅可以解释回声定位蝙蝠的行为表现，而且还可以促进我们对人类语音处理的理解。将讨论三个具体目标。目的#1是定量地表征当以不同脉冲重复率呈现刺激时IC中单个神经元对声音频率的响应选择性，以测试频率选择性取决于刺激速率的假设，即，当音调脉冲以较高的重复率出现时，选择性更大。目标#2是确定幅度选择性变化所需的序列中的音调脉冲的最小数量，以测试IC神经元对声音脉冲的幅度和频率选择性可以在少至一个先前声音脉冲的存在下增强的假设。目的#3是研究单个IC神经元中幅度和频率选择性的速率依赖性的突触后事件，使用细胞外微离子电渗注射技术和细胞内记录来测试当声音脉冲以高于低重复率呈现时抑制更鲁棒的假设。

DESCRIPTION (provided by applicant): The overall aim of this research program is to investigate how the time interval between temporally discrete sounds in a sequence influences the fundamental response properties of central auditory neurons. Sounds produced in sequences are common to most bioacoustics signals such as the biosonar sounds used by bats and communication sounds including speech. Recent studies in the inferior colliculus (IC) of bats show a progressive increase in amplitude selectivity of neurons to sounds in a sequence when the rate of acoustic stimulation is increased. Pilot studies have revealed that the rate of stimulation has a more global impact on an IC unit's responses across several dimensions, including the unit's frequency selectivity. In addition, the ability of human listeners to discriminate small differences in sound level improves with increased rate of acoustic stimulation during psychophysical experiments. Therefore, understanding the mechanisms that underlie rate-dependent changes in amplitude and frequency selectivity could not only explain behavioral performance of echo locating bats, but it could also advance our understanding of speech processing in humans. Three specific aims will be addressed. Aim #1 is to characterize quantitatively the response selectivity's of single neurons in the IC to sound frequency when the stimuli are presented at different pulse repetition rates to test the hypothesis that frequency selectivity is dependent upon the rate of stimulation, i.e., the selectivity is greater when the tone pulses are presented at higher repetition rates. Aim #2 is to determine the minimum number of tone pulses in a train required for a change in amplitude selectivity to test the hypothesis that the amplitude and frequency selectivity's of IC neurons to a sound pulse can be enhanced in the presence of as few as one preceding sound pulse. Aim #3 is to study the postsynaptic events that underlie the rate-dependence in amplitude and frequency selectivity's in single IC neurons, using extracellular microiontophoretic injection techniques and intracellular recording to test the hypothesis that inhibition is more robust when sound pulses are presented at high than low repetition rates.