Neural basis of active sensation: Role of primary afferents

触觉和视觉都是活跃的感官：我们用手在物体上扫来研究物体；我们通过扫视周围的环境来观察环境。同样，大鼠和小鼠的胡须系统是一种活跃的感觉：这些动物通过有节奏地前后摆动胡须（“whisking”）来探索环境。啮齿类动物可以用它们的胡须非常准确地判断物体的位置，但前提是它们能主动移动胡须。由于不同哺乳动物的不同感觉系统具有深刻的相似性，研究胡须可以为有关大脑感知机制的一般问题提供重要的见解。我们目前对须系统的大部分知识都来自于对麻醉动物的研究。这种方法对某些问题仍然有用，但是，在麻醉的动物中，控制胡须运动的肌肉仍然存在。为了充分理解一个活跃的感觉系统，研究清醒的、有行为的动物是至关重要的。然而，在过去，精确地测量醒着的动物的单个胡须是如何运动的是非常困难的。然而，现在已经开发出了克服这一困难的新方法。这是第一次有可能精确测量醒着的大鼠/小鼠的胡须是如何运动的，同时测量相关单个脑细胞的电活动。令人惊讶的是，关于须系统的第一个阶段如何在清醒的动物中运作，有一些基本问题尚不清楚。第一阶段的神经细胞被称为“初级晶须传入”。在这个项目中，我们想要回答的具体问题如下。在一只醒着的老鼠身上，关于须的运动，初级事件向大脑传递了什么信息？原始传入提供的信息是可靠的，还是传入的“噪音”可以解释动物在感知任务中所犯的错误？我们将使用视频速度，高分辨率摄像机来研究这些问题，以精确测量胡须是如何移动的，同时我们测量来自大脑的主要传入活动。拟议中的实验将揭示在主动感知条件下，大脑的输入是什么。这项研究将为开发“神经修复装置”以替代受损神经（例如糖尿病神经病变）提供相关的基础知识。

Touch and vision are both active senses: we investigate objects by sweeping our hands across them; we investigate the environment by scanning our eyes across it. Similarly, the whisker system of rats and mice is an active sense: these animals explore their environment by rhythmically sweeping their whiskers backwards and forwards ('whisking'). Rodents can tell the location of an object very accurately using their whiskers, but only if they can actively move them. Since it is well-established that different sensory systems in different mammals have profound similarities, studying whiskers can offer important insight into general questions about the brain mechanisms of perception.Most of our current knowledge of the whisker system has come from work on anaesthetised animals. This approach continues to be useful for certain questions but, in an anaesthetised animal, the muscles that control whisker movements are still. To fully understand an active sensory system, it is crucial to study awake, behaving animals. However, in the past it was very difficult to accurately measure precisely how individual whiskers move in an awake animal. Now, however, new methods have been developed that overcome this difficulty. For the first time, it is possible to precisely measure how the whiskers of an awake rat/mouse are moving whilst, at the same time, measuring the electrical activity of the relevant individual brain cells.Surprisingly, there are basic issues about how the very first stage in the whisker system operates in the awake animal, that are not understood. The nerve cells at this first stage are known as 'primary whisker afferents'. In this project, the specific questions we want to answer are as follows. In an awake mouse, what information do the primary afferents convey about whisker movements to the brain? Is the information that primary afferents provide reliable, or can afferent 'noise' account for the errors that animals make in perceptual tasks? We will investigate these questions by using a video speed, high resolution video camera to measure precisely how the whiskers are moving at the same time as we measure the activity of primary afferents from the brain. The proposed experiments will reveal what the input to the brain is under active perception conditions. This research will provide basic knowledge that is pertinent to the effort to develop 'neuroprosthetic devices' to replace damaged nerves (e.g., diabetic neuropathy).