Imaging attractor dynamics in the neural compass

单个神经元的工作时间很短；从1毫秒的动作电位持续时间到仅持续10毫秒或100毫秒的突触电流。然而，嵌入在网络中的神经元能够在没有外部刺激的情况下保持持续的活动。一个著名的计算理论使用“吸引子动力学”，即网络的连通性在不增加网络输入的情况下稳定活动。一般来说，这是在网络中实现的，该网络由编码相似特征的神经元之间的经常性兴奋性连接以及用于沉默编码非相似特征的神经元的活动的前馈抑制连接组成。这创造了一个竞争网络，它将在没有任何额外输入的情况下维持其当前的活动，并且在新的输入足够强大以改变吸引子状态之前不会改变。重要的是，该框架可以对离散和连续的模拟变量进行编码。在这里，我们建议寻找头方向(HD)细胞网络中吸引子动力学的证据。HD系统几乎完全使用连续的环形吸引子网络来建模。简单地说，代表当前HD的活动通过传统的吸引器连接来维持，而活动通过前庭输入逐渐沿着这个连续的环形吸引器移动，前庭输入传递动物的头部运动。我们将使用包含丰富HD细胞的丘脑前核(ATN)的光学成像，试图在行为自由的小鼠中可视化这种活动。我们将使用并进一步开发微型显微镜，使我们能够同时从数百个HD细胞进行记录。与传统的电极记录相比，这种方法是一个重大改进，研究人员一次只能记录多达10个HD细胞。我们将调查头部方向网络中是否存在类吸引子动力学。我们将开发闭环系统的硬件和软件，以基于轻微的头部运动来执行光遗传扰动，在各种行为下对HD细胞进行光学成像，以寻找网络中的环吸引子和相干漂移，最后将执行HD生成电路的光遗传沉默，以确定诱导和分析HD网络中的较大漂移，并将此较大漂移与路径整合任务中的行为进行比较。这些实验将首次提供大量HD细胞的光学记录，并将深入了解HD网络的网络动态。

Individual neurons work on short timescales; from an action potential duration of 1 ms to synaptic currents that persist for just 10 ms or 100 ms of milliseconds. Yet, neurons embedded within a network are capable of maintaining persistent activity in the absence of external stimuli. One prominent computational theory uses 'attractor dynamics', whereby the connectivity of the network stabilizes activity without additional input to the network. In general, this is implemented in network that consists of recurrent excitatory connections between neurons that code for similar features along with feedforward inhibitory connectivity to silence the activity of neurons coding for non-similar features. This creates a competitive network that will sustain its current activity without any additional input, and will not change until a new input is strong enough to change the attractor state'. Importantly, this framework can encode discrete and continuous analog' variables. Here we propose to look for evidence of attractor dynamics in the head direction (HD) cell network.? ******The HD system has almost exclusively been modeled using a continuous ring attractor network. Briefly, activity representing the current HD is maintained by traditional attractor connectivity, while activity is gradually moved along this continuous ring attractor by vestibular inputs that relay head movements of the animal. We will use optical imaging in the anterior thalamic nucleus (ATN), which contains abundant HD cells, in an attempt to visualize this activity in freely behaving mice. We will use and further develop miniaturized microscopes that will allow us to record from hundreds of HD cells simultaneously. This approach is a major improvement over traditional electrode recordings, with which researchers have only recorded from up to 10 HD cells at a time. We will investigate whether attractor-like dynamics exist within the head direction network. We will develop the hardware and software for a closed-loop system to perform optogenetic perturbations based on slight head movements, perform optical imaging of HD cells in a variety of behaviors to look for ring attractors and coherent drift in the network, and finally will perform optogenetic silencing of the HD generation circuitry to determine to induce and analyze larger shifts in the HD network and compare this larger drift to behavior in a path integration task. These experiments will provide the first optical recordings of large populations of HD cells and will provide insight into the network dynamics of the HD network.