Neural mechanisms for decoding olfactory information in Drosophila

神经编码是大脑将感觉刺激转化为神经元内电活动模式的过程，对感觉指导行动至关重要。尽管这很重要，但人们对此知之甚少。 神经编码实际上是由大脑中的下游网络使用--或“解码”的。这一差距是由于两个 基本挑战：(1)以时空精度对代码进行因果扰动，以及(2)测量已识别的突触后目标神经元的结果活动。 在这里，我们建议克服这些挑战，通过在一个易于处理的实验系统中研究嗅觉神经编码是如何被其下游网络解码的：果蝇，果蝇。我们已经开发出一种新的方法，可以将尖峰模式“写入”具有单细胞类型的中央投射神经元群体。 分辨率使用双光子光遗传学，同时记录他们的突触后目标神经元，我们有 最近确认的。这使得能够直接因果控制嗅觉神经种群编码的精确的尖峰特征。在目标1中，我们将用双光子光遗传学控制投射神经元中尖峰频率和相对尖峰潜伏期的组合模式，以确定这些模式是如何被下游神经元解码的。在目标2中，我们将结合双光子光遗传刺激和嗅觉刺激来研究如何 感官适应改变了解码的逻辑。在目标3中，我们将测试下游神经元 它们自己被灵活地解码为依赖饥饿的趋化行为。总而言之，这些研究将揭示 大脑对自己的嗅觉神经编码进行解码的基本机制。 尽管苍蝇和哺乳动物之间存在差异，但神经编码的基本逻辑在无脊椎动物和脊椎动物之间是非常保守的。这些相似之处表明，在 果蝇将与其他动物的解码机制相关。更透彻地了解 大脑内的神经解码原理有可能改变新大脑的发展-- 可以改善脑损伤患者预后的机器接口。

Neural encoding, the process by which the brain converts sensory stimuli into patterns of electrical activity within neurons, is critical for sensation to guide action. Despite this importance, little is known about how neural codes are actually used – or “decoded” – by downstream networks in the brain. This gap is due to two basic challenges: (1) causally perturbing the code with spatiotemporal precision, and (2) measuring the resulting activity from identified postsynaptic target neurons. Here, we propose to overcome these challenges, by investigating how an olfactory neural code is decoded by its downstream network in a tractable experimental system: the fruit fly, Drosophila. We have developed new methods to “write” spike patterns into populations of central projection neurons with single cell-type resolution using 2-photon optogenetics, while recording from their postsynaptic target neurons, which we have recently identified. This enables direct causal control of precise spiking features of the olfactory neural population code. In Aim 1, we will control combinatorial patterns of spike rates and relative spike latencies in projection neurons with 2-photon optogenetics to determine how these patterns are decoded by downstream neurons. In Aim 2, we will combine 2-photon optogenetic stimulation with olfactory stimulation to examine how sensory adaptation changes the logic of decoding. In Aim 3, we will test how the downstream neurons are themselves flexibly decoded into hunger-dependent chemotaxis behavior. Together, these studies will reveal basic mechanisms by which the brain decodes its own neural code for olfaction. Although there are differences between flies and mammals, the basic logic of neural coding is remarkably conserved between invertebrates and vertebrates. These similarities suggest that discoveries made in the fruit fly will be relevant to the mechanisms of decoding in other animals. A more thorough understanding of the principles of neural decoding within the brain has the potential to transform the development of novel brain- machine interfaces that could improve the outcomes of patients with brain injuries.