Are spatial frequency cues used for whisker-based active discrimination?
Are spatial frequency cues used for whisker-based active discrimination?
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DOI：
10.3389/fnbeh.2014.00379
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发表时间：
2014-11-03
影响因子：
3
通讯作者：
Schwarz, Cornelius
中科院分区：
文献类型：
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作者：
Georgieva, Petya;Brugger, Dominik;Schwarz, Cornelius
老鼠非常擅长通过触须的动作来辨别物体和质地。如果他们使用空间频率线索，他们将能够以刺激依赖的方式优化性能，通过在纹理表面上更快或更慢地移动他们的须，从而将神经元信号的频率内容转移到感知的最佳工作范围。我们通过测量头部固定的大鼠的辨别表现来测试这个想法，这些大鼠被训练从虚拟网格中主动取样。虚拟网格模拟了由真实物体（例如，树丛模式）产生的离散和重复的晶须偏转，并将单个电微刺激脉冲直接传递到桶状皮层，并提供了可以以最高精度控制刺激的关键优势。令人惊讶的是，大鼠不能理所当然地利用空间频率线索进行辨别，也不能适应搅拌模式，以最佳地利用频率差异。与之形成鲜明对比的是，它们可以很容易地被训练来辨别电脉冲振幅不同的刺激，这是一种不能通过搅拌而改变的刺激特性。将这些“容易区分”的区别与其他只提供频率/位置线索的区别混合在一起，可以引导老鼠基于频率和/或位置进行区分，尽管这是基于较低水平的表现。在这种训练之后，取消电振幅提示和减少位置提示导致了最初的良好表现，然而，在数百次试验的过程中，这种表现并不稳定，并下降到非常低的水平。这些结果清楚地表明，频率线索，虽然肯定被大鼠感知，是次要的，他们不能支持一致的调制搅拌模式，以优化性能。
Rats are highly skilled in discriminating objects and textures by palpatory movements of their whiskers. If they used spatial frequency cues, they would be able to optimize performance in a stimulus dependent way by moving their whisker faster or slower across the texture surface, thereby shifting the frequency content of the neuronal signal toward an optimal working range for perception. We tested this idea by measuring discrimination performance of head fixed rats that were trained to actively sample from virtual grids. The virtual grid mimicked discrete and repetitive whisker deflections generated by real objects (e.g., grove patterns) with single electrical microstimulation pulses delivered directly to the barrel cortex, and provided the critical advantage that stimuli could be controlled at highest precision. Surprisingly, rats failed to use the spatial frequency cue for discrimination as a matter of course, and also failed to adapt whisking patterns in order to optimally exploit frequency differences. In striking contrast they could be easily trained to discriminate stimuli differing in electrical pulse amplitudes, a stimulus property that is not malleable by whisking. Intermingling these "easy-to-discriminate" discriminanda with others that solely offered frequency/positional cues, rats could be guided to base discrimination on frequency and/or position, albeit on a lower level of performance. Following this training, abolishment of electrical amplitude cues and reducing positional cues led to initial good performance which, however, was unstable and ran down to very low levels over the course of hundreds of trials. These results clearly demonstrate that frequency cues, while definitely perceived by rats, are of minor importance and they are not able to support consistent modulation of whisking patterns to optimize performance.