Synaptic mechanisms of coding transformations in auditory cortex

描述（由申请人提供）：本研究的长期目标是了解听觉皮层的突触处理如何改变时间结构声音（如音乐和语音）的神经表征。本提案的重点是测试关于突触抑制如何将声音表征从时间编码转换为速率编码的特定假设。这种转换可能支持多感觉整合，因为来自不同动态的感觉区域的信息可能需要转换成一个共同的速率代码，以便有意义地组合。这一过程背后的突触机制尚不清楚。目的1将测试听觉皮层中持续的速率编码反应是否由刺激特异性突触抑制减少产生。目的2将测试对周期性刺激的速率编码反应是否由刺激特异性突触抑制减少产生。目的3将测试周期性刺激的对手加工是否通过突触推拉机制发生。为了实现这些目标，我们将使用来自大鼠听觉皮质神经元的全细胞电压钳记录来测量最佳音调和周期性刺激引起的兴奋和抑制。这些实验将有助于阐明突触机制，改变时间结构的声音如何在听觉皮层中编码。由于时间结构提供了对语音感知至关重要的信息，听觉皮层中时变信号的突触处理与我们对语音处理机制的理解尤其相关。因此，所提出的研究将有助于我们对涉及语言感知的皮层突触机制的基本理解。

DESCRIPTION (provided by applicant): The long-term objective of this research is to understand how synaptic processing in auditory cortex transforms the neural representation of temporally structured sounds such as music and speech. The focus in this proposal is to test specific hypotheses about how synaptic inhibition transforms the representation of sound from a temporal code into a rate code. This transformation may support multi-sensory integration, because information from sensory areas with different dynamics may need to be converted into a common rate code to be meaningfully combined. The synaptic mechanisms underlying this process remain unknown. Aim 1 will test whether sustained rate-coded responses in auditory cortex are generated by a stimulus-specific decrease in synaptic inhibition. Aim 2 will test whether rate-coded responses to periodic stimuli are generated by a stimulus-specific decrease in synaptic inhibition. Aim 3 will test whether opponent processing of periodic stimuli occurs by a synaptic push-pull mechanism. To accomplish these aims, we will use whole-cell voltage clamp recordings from rat auditory cortical neurons to measure the excitation and inhibition evoked by optimal tones and periodic stimuli. These experiments will help to elucidate the synaptic mechanisms that transform how temporally structured sounds are encoded in auditory cortex. Because temporal structure provides information critical for speech perception, the synaptic processing of time-varying signals in auditory cortex is especially relevant to our understanding of the mechanisms underlying speech processing. The proposed studies will therefore contribute to our basic understanding of the cortical synaptic mechanisms involved in speech perception. PUBLIC HEALTH RELEVANCE: Language-learning impaired children show profound deficits in the processing of temporally structured sound, but specific auditory training can speed up auditory processing in these children and lead to improved speech processing. The proposed studies will provide insight into how the representation of this temporal structure is transformed by synaptic processing in auditory cortex. In the long term, a greater understanding of the mechanisms that contribute to speech processing in auditory cortex will likely influence the development of improved rehabilitation strategies for language impairments.