Kerekes Pauline, Daret Aurélie, Shulz Daniel E, Ego-Stengel Valérie
Unité de Neuroscience, Information et Complexité, Centre National de la Recherche Scientifique, FRE 3693, 91198 Gif-sur-Yvette, France.
Unité de Neuroscience, Information et Complexité, Centre National de la Recherche Scientifique, FRE 3693, 91198 Gif-sur-Yvette, France
J Neurosci. 2017 Aug 9;37(32):7567-7579. doi: 10.1523/JNEUROSCI.0528-17.2017. Epub 2017 Jun 29.
A majority of whisker discrimination tasks in rodents are performed on head-fixed animals to facilitate tracking or control of the sensory inputs. However, head fixation critically restrains the behavior and thus the incoming stimuli compared with those occurring in natural conditions. In this study, we investigated whether freely behaving rats can discriminate fine tactile patterns while running, in particular when stimuli are presented simultaneously on both sides of the snout. We developed a two-alternative forced-choice task in an automated modified T-maze. Stimuli were either a surface with no bars (smooth) or with vertical bars spaced irregularly or regularly. While running at full speed, rats encountered simultaneously the two discriminanda placed on the two sides of the central aisle. Rats learned to recognize regular bars versus a smooth surface in 8 weeks. They solved the task while running at an average speed of 1 m/s, so that the contact with the stimulus lasted <1 typical whisking cycle, precluding the use of active whisking. Whisker-tracking analysis revealed an asymmetry in the position of the whiskers: they oriented toward the rewarded stimulus during successful trials as early as 60 ms after the first possible contact. We showed that the whiskers and activity in the primary somatosensory cortex are involved during the discrimination process. Finally, we identified irregular patterns of bars that the rats can discriminate from the regular one. This novel task shows that freely moving rodents can make simultaneous bilateral tactile discrimination without whisking. The whisker system of rodents is a widely used model to study tactile processing. Rats show remarkable abilities in discriminating surfaces by actively moving their whiskers (whisking) against stimuli, typically sampling them several times. This motor strategy affects considerably the way that tactile information is acquired and thus the way that neuronal networks process the information. However, when rats run at high speed, they protract their whiskers in front of the snout without large movements. Here, we investigated whether rats are able to discriminate regular and irregular patterns of vertical bars while running without whisking. We found that the animals can perform a bilateral simultaneous discrimination without whisking and that this involves both whiskers and barrel cortex activity.
在啮齿动物中，大多数须毛辨别任务是在头部固定的动物身上进行的，以便于追踪或控制感觉输入。然而，与自然条件下相比，头部固定严重限制了行为以及传入的刺激。在本研究中，我们调查了自由活动的大鼠在奔跑时是否能够辨别精细的触觉模式，特别是当刺激同时出现在口鼻两侧时。我们在一个自动改良的T型迷宫中开发了一种二选一强迫选择任务。刺激物要么是没有条纹的表面（光滑），要么是垂直条纹间隔不规则或规则的表面。大鼠在全速奔跑时，会同时遇到放置在中央通道两侧的两个辨别物。大鼠在8周内学会了识别规则条纹与光滑表面。它们在以平均1米/秒的速度奔跑时解决了任务，因此与刺激的接触持续时间小于1个典型的须动周期，排除了主动须动的使用。须毛追踪分析揭示了须毛位置的不对称性：在成功试验中，它们早在首次可能接触后60毫秒就朝着奖励刺激的方向定向。我们表明，须毛和初级体感皮层的活动在辨别过程中发挥作用。最后，我们确定了大鼠能够与规则条纹区分开来的不规则条纹模式。这项新任务表明，自由移动的啮齿动物可以在不须动的情况下进行同时双侧触觉辨别。啮齿动物的须毛系统是研究触觉处理的广泛使用的模型。大鼠通过主动将须毛（须动）对着刺激移动来辨别表面，通常会对其进行多次采样，表现出显著的能力。这种运动策略极大地影响了触觉信息的获取方式，进而影响了神经网络处理信息的方式。然而，当大鼠高速奔跑时，它们会在口鼻前方伸出须毛，且动作不大。在此，我们调查了大鼠在不须动的情况下奔跑时是否能够辨别垂直条纹的规则和不规则模式。我们发现，动物可以在不须动的情况下进行双侧同时辨别，并且这涉及须毛和桶状皮层的活动。
