Neuronal processing of task-specific afferent whisker information in the rat barrel cortex

大鼠通过触须的触觉运动高度熟练地辨别物体和纹理。我们问的问题是否任务特定的搅拌策略优化感知，如果是这样的话，优化感知的神经元相关的是在胡须感觉运动皮层。在第一个资助期，我们着手研究的假设，纹理的空间频率转换成时间频率的触觉通路上的神经元活动的搅拌决定搅拌参数的选择。实现所需的精确实验控制（尽管胡须运动）的方法技巧是实现虚拟现实环境。头部固定的大鼠进行训练，以区分虚拟网格中，凭借实时反馈的胡须的位置，胡须的通过每个网格点的动物提出的电微刺激在其初级传入。提供强有力的证据反对我们的假设，我们发现心理测量性能差，缺乏系统的适应搅拌策略。匹配这一结果，一种新的被动歧视任务，采用脉动晶须偏转，表明不是频率，而是运动事件（瞬时振幅或速度）是决定性的振动触觉歧视。在以前的生物力学研究中，其他人，运动学事件是依赖于触诊纹理的粗糙度已被描述。这些所谓的“滑动”是由于胡须的生物力学弹性。在这些见解的指导下，我们修改了我们的工作假设。现在，我们建议调查是否是发生的概率和运动学特征的“滑”事件，是变量进行优化，通过主动触觉感知。为此，我们将首先进行生物力学测量，以找出滑动概率和运动学特征是否取决于晶须在纹理上的相对运动。其次，我们问大鼠执行的歧视任务是否会改变他们的搅拌模式预测从测得的滑动模式和由此产生的变化的可辨别性。在第二个项目中，我们将使用虚拟纹理歧视的任务，以发挥最高的实验控制和调查，在更分析的方式，是否以及如何定义的滑动模式和他们的依赖胡须运动影响搅拌策略的大鼠。在所有的实验中，多电极单元记录将有助于确定是否在触须运动皮层和桶柱的神经元信号处理的任务特定的方式，以及它们是否和如何反映在运动程序的关键变化的信息。

Rats are highly skilled in discriminating objects and textures by palpatory movements of their vibrissae. We ask the question whether task-specific whisking strategies optimize perception, and if so, what the neuronal correlate of optimized perception is in whisker sensorimotor cortex. In the first funding period we set out to study the hypothesis that the conversion of a texture’s spatial frequency into a temporal frequency of neuronal activity on the tactile pathway by whisking determines the choice of whisking parameters. The methodological trick to exert the desired exact experimental control (despite whisker movements) was to realize a virtual reality environment. Head-fixed rats were trained to discriminate virtual grids in which, by virtue of real-time feedback of the whisker position, the whisker’s passing of each grid point was presented to the animal by an electrical microstimulation in its primary afferents. Providing strong evidence against our hypothesis, we found poor psychometric performance and a lack of systematic adaptation of whisking strategy. Matching this result, a novel passive discrimination task employing pulsatile whisker deflections, showed that NOT frequency but rather kinematic events (instantaneous amplitude or velocity) are decisive for vibrotactile discrimination. In previous biomechanical studies by others, kinematic events which are dependent on the roughness of the palpated texture had been described. These so-called ‘slips’ are due to the biomechanical elasticity of the whisker. Guided by these insights we modified our working hypothesis. We now propose to investigate whether it is the probability of occurrence and the kinematic characteristics of ‘slip’ events that is the variable to be optimized by active tactile perception. To this end, we will first perform biomechanical measurements to find out if slip probability and kinematic characteristics are dependent on relative movement of the whisker across a texture. Secondly, we ask whether rats performing a discrimination task will change their whisking pattern as predicted from the measured slip patterns and the resulting changes in discriminability. In a second project we will use the virtual texture discrimination task to exert highest experimental control and investigate in a more analytical way, whether and how defined slip patterns and their dependence on whisker movements affect the whisking strategies of rats. In all experiments, multi-electrode unit recordings will help to determine whether neuronal signals in the whisker motor cortex and the barrel column are processed in a task specific way and whether and how they reflect information about critical changes in the motor program.