Waiblinger Christian, Brugger Dominik, Whitmire Clarissa J, Stanley Garrett B, Schwarz Cornelius
Systems Neurophysiology, Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen Tübingen, Germany ; Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen Tübingen, Germany ; Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University Atlanta, GA, USA.
Systems Neurophysiology, Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen Tübingen, Germany ; Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen Tübingen, Germany.
Front Integr Neurosci. 2015 Oct 15;9:53. doi: 10.3389/fnint.2015.00053. eCollection 2015.
Rodents use active whisker movements to explore their environment. The "slip hypothesis" of whisker-related tactile perception entails that short-lived kinematic events (abrupt whisker movements, called "slips", due to bioelastic whisker properties that occur during active touch of textures) carry the decisive texture information. Supporting this hypothesis, previous studies have shown that slip amplitude and frequency occur in a texture-dependent way. Further, experiments employing passive pulsatile whisker deflections revealed that perceptual performance based on pulse kinematics (i.e., signatures that resemble slips) is far superior to the one based on time-integrated variables like frequency and intensity. So far, pulsatile stimuli were employed in a noise free environment. However, the realistic scenario involves background noise (e.g., evoked by rubbing across the texture). Therefore, if slips are used for tactile perception, the tactile neuronal system would need to differentiate slip-evoked spikes from those evoked by noise. To test the animals under these more realistic conditions, we presented passive whisker-deflections to head-fixed trained rats, consisting of "slip-like" events (waveforms mimicking slips occurring with touch of real textures) embedded into background noise. Varying the (i) shapes (ramp or pulse); (ii) kinematics (amplitude, velocity, etc.); and (iii) the probabilities of occurrence of slip-like events, we observed that rats could readily detect slip-like events of different shapes against noisy background. Psychophysical curves revealed that the difference of slip event and noise amplitude determined perception, while increased probability of occurrence (frequency) had barely any effect. These results strongly support the notion that encoding of kinematics dominantly determines whisker-related tactile perception while the computation of frequency or intensity plays a minor role.
啮齿动物通过主动的触须运动来探索它们的环境。与触须相关的触觉感知的“滑动假说”认为，短暂的运动学事件（由于在主动触摸纹理时触须的生物弹性特性而产生的突然的触须运动，称为“滑动”）携带了决定性的纹理信息。支持这一假说的是，先前的研究表明，滑动幅度和频率以与纹理相关的方式出现。此外，采用被动脉动触须偏转的实验表明，基于脉冲运动学（即类似于滑动的特征）的感知性能远优于基于频率和强度等时间积分变量的感知性能。到目前为止，脉动刺激是在无噪声环境中使用的。然而，实际场景中存在背景噪声（例如，由在纹理上摩擦引起）。因此，如果滑动用于触觉感知，触觉神经系统将需要区分由滑动引起的尖峰和由噪声引起的尖峰。为了在这些更现实的条件下测试动物，我们向头部固定的训练大鼠呈现被动触须偏转，其中包括嵌入背景噪声中的“类似滑动”事件（模仿触摸真实纹理时发生的滑动的波形）。通过改变（i）形状（斜坡或脉冲）；（ii）运动学（幅度、速度等）；以及（iii）类似滑动事件的发生概率，我们观察到大鼠能够很容易地在嘈杂背景中检测到不同形状的类似滑动事件。心理物理学曲线表明，滑动事件和噪声幅度的差异决定了感知，而增加的发生概率（频率）几乎没有任何影响。这些结果有力地支持了这样一种观点，即运动学编码在很大程度上决定了与触须相关的触觉感知，而频率或强度的计算起次要作用。
