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征的刺激特征，并理解这种表征的保真度，是理解大脑如何处理感官世界的核心。在哺乳动物嗅球中，二尖瓣/簇状（M/T）细胞既接受来自感觉神经元的突触输入，又作为中枢大脑结构的主要输出。由于物理限制，脊椎动物嗅觉受体的气味强度（浓度）变化可能比视觉或听觉等其他感觉模式的刺激强度变化要慢得多。由于这种速度限制，动作电位（ap）的精确计时不能像其他感觉系统那样跟踪刺激特性在毫秒级的快速变化。相反，精确的AP计时提供的额外“带宽”可以编码其他嗅觉刺激特征，比如身份或环境。如果气味识别在刺激反应早期的AP时间中被编码，并且这个时间在相同的刺激中是可靠的，那么行为反应延迟可以最小化11。在整个呼吸周期中，一个相同的整体AP反应可以用来确认气味的身份。或者，这种反应在不同周期中的定向变化可能在每个呼吸周期中传递有关复杂刺激的新信息。在这里，我提议测试一种假设，即集合AP时间编码小鼠嗅球中气味刺激的特征，并在呼吸周期中以动态的方式进行编码。

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.