Werner Reichardt Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen Germany.
Neuron. 2010 Feb 25;65(4):530-40. doi: 10.1016/j.neuron.2010.02.007.
Understanding the neural code underlying perception requires the mapping of physical stimulus parameters to both psychophysical decisions and neuronal responses. Here, we employed a novel psychophysical task in head-fixed rats to measure discriminability of vibrotactile whisker deflections. Rats could discriminate 90 Hz from 60 Hz pulsatile stimuli if stimulus intensity covaried with frequency. To pin down the physical parameters used by the rats to discriminate these vibrations, we manipulated stimulus amplitude to arrive at pairs of nondiscriminable stimuli. We found that vibrations matched in intensity (measured as mean absolute velocity), but differing in frequency, were no longer discriminable. Recordings of trigeminal ganglion neurons revealed that the distribution of neurometric sensitivities based on spike counts, but not interspike intervals, matched the rats' inability to discriminate intensity-matched stimuli. In conclusion, we suggest that stimulus mean absolute velocity, encoded in primary afferent spike counts, plays a prominent role for whisker-mediated perception.
理解感知背后的神经编码需要将物理刺激参数映射到心理物理决策和神经元反应上。在这里，我们在固定头部的大鼠中采用了一种新的心理物理任务来测量触须振动的可辨别性。如果刺激强度随频率变化，大鼠可以将 90 Hz 与 60 Hz 的脉动刺激区分开来。为了确定大鼠用于区分这些振动的物理参数，我们操纵刺激幅度以获得无法区分的刺激对。我们发现，强度匹配（以平均绝对速度衡量）但频率不同的振动不再可区分。三叉神经节神经元的记录显示，基于尖峰计数的神经测量敏感性分布，但不是尖峰间隔，与大鼠无法区分强度匹配的刺激相匹配。总之，我们认为刺激的平均绝对速度，由初级传入尖峰计数编码，在触须介导的感知中起着重要作用。
