弱背景噪声对大鼠听皮层神经元频率调谐的影响

在自然环境中,人和动物常在一定的背景噪声下感知信号声刺激,然而,关于低强度的弱背景噪声如何影响听皮层神经元对声刺激频率的编码尚不清楚.本研究以大鼠听皮层神经元的频率反应域为研究对象,测定了阈下背景噪声对79个神经元频率反应域的影响.结果表明,弱背景噪声对大鼠初级听皮层神经元的听反应既有抑制性影响、又有易化性影响.一般来说,抑制性影响使神经元的频率调谐范围和最佳频率反应域缩小,易化性影响使神经元的频率调谐范围和最佳频率反应域增大.对于少数神经元,弱背景噪声并未显著改变其频率调谐范围,但却改变了其最佳频率反应域范围.弱背景噪声对63.64%神经元的特征频率和55.84%神经元的最低阈值无显著影响.神经元频率调谐曲线的尖部比中部更容易受到弱背景噪声的影响.该研究结果有助于我们进一步理解复杂声环境下大脑听皮层对听觉信息的编码机制.

The Effect of Weak Background Noise on The Frequency Tuning of Neurons in The Rat Auditory Cortex

In natural environment, human and animals often percept signal sound stimuli in background noise conditions. However, it is not clear how the low-level weak background noise affect the coding of frequency tuning of auditory cortical neurons. In the present study, we determined how weak background noise affected the frequency response area of 79 neurons in the rat primary auditory cortex. The results demonstrated that weak background noise either suppressed or facilitated the responses of some cortical neurons to sound stimuli. Generally, the suppression of responses by weak background noise reduced the extent of frequency tuning and the extent of best frequency response area of auditory cortical neurons, and the facilitation of responses by weak background noise enlarged the extent of frequency tuning and the best response areas of the affected neurons. For a minority of neurons, weak background noise did not significantly change their extent of frequency tuning, but changed their extent of best frequency response area. Weak background noise did not change the characteristic frequency of 63.64% of the sample neurons and the minimum threshold of 55.84% of the sampled neurons. The tip of the frequency tuning curves of auditory cortical neurons was more susceptible to be affected by the background noise than the middle part of the frequency tuning curves of these neurons.