清醒大鼠听皮层对复杂空间信息的适应性

The ability to detect unexpected deviant clues in the nature scenario is critical for survival. The stimulus-specific adaptation (SSA) has been regarded as the neuronal correlates for change detection. The SSA in the frequent domain has been extensively examined along the auditory pathway including the primary auditory cortex. However, it has remained fundamentally unclear how the auditory system detects the unexpected sound location. A few researches reported that frequent SSA could enhance the frequent discriminability for deviant stimuli, but those studies failed to uncover the mechanisms underlying it. Basically, the discriminability through ROC analysis relies on two properties: neuronal variance and tuning slope. We will take those two factors into account to understand why SSA facilitates the spatial discriminability if spatial SSA could. Then our next topic is about the spatial regularity recognition or adaptation, which is fundamental for the auditory pattern recognition. The spatial regularity research has never been addressed in the electrophysiology field at the single neuron level. Meanwhile, the deviant subject always appears coupling with both spatial deviant information and frequent deviant information, however, the auditory researches usually focused on only one item each time, can the spatial and frequent information interact in SSA? We will tackle all issues above by recording neuronal response in the auditory cortex of awaken rats to deviant location, spatial regularity, and jointed deviance cross space and frequency, and use ROC analysis to calculate the spatial discriminability with the following four specific aims:.Specific Aim 1: We will seek how auditory cortex detects unexpected sound location and how spatial SSA changes the spatial discriminability..Specific Aim 2: We will compare responses between regular and irregular spatial oddball paradigms to find how the auditory system respond to the spatial regularity and whether the spatial regularity adaptation modifies the spatial discriminability or not..Specific Aim 3: We will investigate whether and how spatial and frequent information interact through SSA..Specific Aim 4: We will investigate large-scale tonotopic organization in the auditory cortex about the spatial information processing such as spatial discriminability, spatial SSA strength, spatial regularity adaptation, left-right discrimination threshold..Results from these experiments will contribute important knowledge to our current understanding about how the auditory system detects unexpected sound location, how neuronal slope/variance shapes perception, how frequent and spatial information interact to facilitate the deviance detection, and what the specific function is during the spatial localization for different auditory cortical areas.

检测新鲜刺激对动物生存至关重要。神经元通过SSA（stimulus specific adaptation）实现对新鲜刺激的检测。在频率SSA上人们做了大量工作，但在空间SSA上人们还不清楚，听皮层神经元是否对新鲜位置敏感？更进一步的,听皮层神经元是否对空间组合规则敏感？组合规则是模式识别的基础。人们发现频率SSA提高对新鲜刺激的分辨能力，但不清楚其机制。新事物的出现总是在频率和空间上耦合的，人们大都孤立地去研究频率和空间上的信息，两者能否在SSA上交互作用？本项目以清醒大鼠为对象，来研究听皮层神经元对新鲜位置，空间组合规则，频率空间双重新鲜刺激的反应，并结合ROC分析来计算空间分辨能力，从而探讨听皮层空间SSA、空间组合规则适应性、频率空间交互作用三者可能的生理功能；以及发挥这些功能的机制；并在整个听皮层大尺度下研究相关空间信息处理的拓扑分布情况。

迅速检测周围环境中突然出现的新鲜刺激，对动物的生存至关重要。听觉系统对短时程和长时程的规律信息具有不同的检测机制，分别对应刺激特异适应性（SSA）和规律敏感性（Regularity）。SSA 是指神经元会对新鲜刺激表现出更强的反应，Regularity 是指神经元对刺激组合规律的敏感性。SSA可能是新鲜检测的一项重要机制，目前对SSA的研究主要利用纯音组成的频率oddball范式，虽然揭示了频率SSA在听觉通路中的强度变化规律，但却忽略了声音的其他特征，比如声音的空间位置特征。同时，自然环境中出现的新鲜刺激往往同时包含多种特征，但之前的工作仅局限于声音的某一特征，因此尚不清楚SSA中是否存在多种声音特征的耦合。Regularity 的研究也只集中在AC中，而SSA与Regularity之间的关系也知之甚少。我们在大鼠的听觉系统中采用细胞外电生理技术，利用多种oddball范式将刺激组合由频率过渡到复杂自然声，从单一特征到空间特征与个体特征的耦合，逐渐模拟真实的生存环境，从而证明：空间位置SSA与频率SSA相似，可能广泛存在于听觉通路中并发挥着重要作用；SSA中存在两种特征的耦合，说明新鲜事件的检测会受益于不同特征信息的整合。同时，听觉丘脑内侧膝状体具备从背景中感知声音变化的能力但对声音的规则组合不太敏感，听觉系统的Regularity可能起源于听觉皮层。该结论为听觉系统中短时程和长时程规律信息的表征提供了新的证据。另外，我们还从听皮层的不同亚区观察SSA的生理特性，结果表明相比于听觉皮层的核心区域，背侧带存在更宽的频谱和更长的时间尺度处理听觉信息，反映了听觉皮层的功能性层级分布。进一步加深了我们对听觉系统新鲜检测生理机制的理解。

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