TEMPORAL DYNAMICS OF CENTRAL AUDITORY PROCESSING

描述（由申请人提供）：本研究计划的总体目的是研究时间上离散的声音序列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。按顺序产生的声音在大多数生物声学信号中是常见的，比如蝙蝠使用的生物声纳声音和包括说话在内的交流声音。最近对蝙蝠下丘（IC）的研究表明，当声刺激的频率增加时，神经元对声音的振幅选择性按顺序逐渐增加。初步研究表明，增产速度对集成电路单元在多个方面的响应具有更全面的影响，包括单元的频率选择性。此外，在心理物理实验中，人类听者辨别细微声级差异的能力随着声刺激频率的增加而提高。因此，理解振幅和频率选择性的速率依赖变化的机制不仅可以解释回声定位蝙蝠的行为表现，还可以促进我们对人类语言处理的理解。将讨论三个具体目标。目的1是定量表征IC中单个神经元对声音频率的反应选择性，当刺激以不同的脉冲重复率呈现时，以测试频率选择性取决于刺激率的假设，即，当音调脉冲以较高的重复率呈现时，选择性更大。目标2是确定振幅选择性变化所需的最小音调脉冲数，以测试IC神经元对声音脉冲的振幅和频率选择性可以在少量声音脉冲存在的情况下增强的假设。目的3是研究单个IC神经元中振幅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泳注射技术和细胞内记录来验证当声音脉冲以高重复率呈现比低重复率呈现时抑制更强的假设。

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.