Cortical processing of olfactory stimuli

描述（申请人提供）：感觉信息的皮质加工在感觉辨别、物体识别和记忆中起着关键作用。大脑皮层的感觉处理过程是高度动态的，过去的经验、当前的环境和期望塑造了人们如何每时每刻地感知世界。感觉加工障碍是中枢神经系统疾病和衰老以及精神分裂症和自闭症等先天性疾病引起的损伤的主要组成部分。在嗅觉系统中，气味分子和混合物的特征被认为是由受体片上的一大家族嗅觉受体蛋白提取的，并通过与嗅球的突触处理进一步定义。目前关于嗅觉功能的观点表明，将这些特征重新组装成感知气味整体的过程主要是由初级嗅觉皮层中的回路完成的。在该奖项过去的资助期内完成的工作提供了证据，证明梨状皮质神经元的气味编码是高度动态的，并且似乎与该皮层的经验依赖合成作用相一致。此外，有证据表明，梨状皮质前神经系统编码气味识别，而梨状皮质后神经系统编码气味质量。在新皮层感觉系统中，经验依赖的物体编码和感知严重依赖于内在的、皮层内的关联纤维。梨状皮质中也存在一个类似的、高度可塑性的内在关联系统，事实上，与梨状皮质前部相比，梨状皮质后部的树突树占主导地位。本研究采用单单元、多单单元和行为技术研究梨状皮质内禀纤维系统在气味编码和感知中的作用。目标1提出参数化研究梨状皮质如何满足模式完成（在恒定刺激中对微小差异的概括）和模式分离（对相似气味的辨别）之间的平衡需求，并将其转化为行为。目标2提出进一步研究经验对梨状皮质前侧和后侧模式完成和分离的影响。目的3研究气味经验诱导的皮层内连接的可塑性及其在皮层集合形成和气味识别中的作用。皮层网络的信息处理对于正常的感觉知觉、记忆和对环境的运动反应至关重要。了解信息是如何被这些网络输入和分析的，将对我们解释和治疗这些基本认知功能障碍的能力产生根本性的影响。这一建议利用嗅觉系统相对简单的组织结构及其强大的可塑性来研究感官体验如何改变皮层回路功能。

DESCRIPTION (provided by applicant): Cortical processing of sensory information plays a critical role in sensory discrimination, object recognition and memory. Cortical sensory processing has been shown to be highly dynamic, with past experience, current context and expectations shaping how the world is perceived on a moment by moment basis. Disorders of sensory processing constitute a major component of impairments induced by CNS disease and aging, as well as congenital disorders such as schizophrenia and autism. In the olfactory system, features of odorant molecules and mixtures are believed to be extracted by a large family of olfactory receptor proteins at the receptor sheet, and further defined by synaptic processing with the olfactory bulb. Current views of olfactory function suggest that re- assembly of these features into perceptual odor wholes is performed largely by circuits in the primary olfactory cortex. Work completed during the past funding period of this award provided evidence that odor encoding by piriform cortical neurons is highly dynamic, and appears to be consistent with the experience-dependent synthetic role proposed for this cortex. In addition, evidence was obtained suggesting that anterior piriform cortex neural ensembles encode odor identity, while posterior piriform cortical ensembles encode odor quality. Experience-dependent object encoding and perception in neocortical sensory systems is heavily dependent on intrinsic, intracortical association fibers. A similar, highly plastic intrinsic association system exists in the piriform cortex, and in fact dominates dendritic trees in posterior piriform compared to anterior. The present proposal examines the role of the piriform cortical intrinsic fiber system in odor encoding and perception using single-unit, multiple single-unit and behavioral techniques. Aim 1 proposes to parametrically examine how needs for a balance between pattern completion (generalization between slight variance within an otherwise constant stimulus) and pattern separation (discrimination of similar odors) are met in piriform cortex and translated to behavior, Aim 2 proposes to further examine the effects of experience on pattern completion and separation in anterior and posterior piriform cortex, and Aim 3 proposes to examine odor experience-induced plasticity of intrinsic cortical connections and their role of cortical ensemble formation and odor discrimination. Information processing by cortical networks is critical for normal sensory perception, memory, and motor responses to the environment. Understanding how information is entered into, and analyzed by these networks will have a fundamental impact on our ability to interpret and treat disorders of these basic cognitive functions. This proposal takes advantage of the relatively simple organization of the olfactory system and its robust plasticity to examine how sensory experience modifies cortical circuit function.