TEMPORAL PRECISION AND DYNAMICAL CODING IN THE OLFACTORY BULB

描述（由申请人提供）：识别由神经元活动表示的刺激特征，并理解这种表示的保真度，对于理解大脑如何处理感觉世界至关重要。在哺乳动物嗅球中，僧帽/簇状（M/T）细胞都接受来自感觉神经元的突触输入，并作为中枢脑结构的主要输出。由于物理限制，脊椎动物气味受体的气味强度（浓度）可能比其他感官形式（如视觉或听觉）的刺激强度变化慢得多。由于这种速度限制，动作电位（AP）的精确计时将不会像其他感觉系统那样跟踪刺激特性的快速毫秒级变化。相反，由精确的AP定时提供的额外“带宽”可以编码其他嗅觉刺激特征，例如身份或上下文。如果气味身份在刺激反应早期被编码在AP定时中，并且该定时在相同的刺激中是可靠的，则行为反应延迟可以被最小化11。在整个呼吸周期中，相同的整体AP反应可以用来确认气味的身份。或者，这种反应在周期中的定向变化可以在每个呼吸周期中传达关于复杂刺激的新信息。在这里，我建议测试的假设，合奏AP定时编码功能的气味刺激在小鼠嗅球，并在整个呼吸周期的动态方式。

DESCRIPTION (provided by applicant): Identification of the stimulus features represented by neuronal activity, and understanding the fidelity of this representation, are central to understanding how the brain processes the sensory world. In the mammalian olfactory bulb, mitral/tufted (M/T) cells both receive synaptic input from sensory neurons, and serve as the principal output to central brain structures. Due to physical constraints, odor intensity (concentration) at odorant receptors in vertebrates is likely to vary much more slowly than stimulus intensity in other sensory modalities such as vision or audition. Because of this speed limit, the precise timing of action potentials (APs) will not track rapid, millisecond-timescale changes in stimulus properties as in other sensory systems. Rather, the extra "bandwidth" afforded by precise AP timing could encode other olfactory stimulus features, such as identity or context. If odor identity is encoded in AP timing early during a stimulus response, and this timing is reliable across identical stimuli, behavioral response latencies could be minimized11. Across respiratory cycles, an identical ensemble AP response could serve to confirm odor identity. Alternatively, directed changes in this response across cycles could convey novel information in each respiratory cycle about a complex stimulus. Here I propose to test the hypotheses that ensemble AP timing encodes features of odor stimuli in the mouse olfactory bulb, and does so in a dynamic fashion across respiratory cycles.