大鼠初级听皮层神经元对声音空间信息的编码

Encoding of Sound Spatial Information by Neurons in The Rat Primary Auditory Cortex

尽管大脑听皮层神经元对声音空间信息的编码已有不少的研究报道,但其编码机制并不十分清楚,相关研究在大鼠的初级听皮层也未见详细的研究报道.用神经电生理学方法在大鼠初级听皮层考察了151个听神经元的听空间反应域,分析了神经元对来自不同空间方位声刺激反应的放电数和平均首次发放潜伏期的关系.结果表明,多数(52.32%)神经元对来自对侧听空间的声刺激反应较强,表现为对侧偏好型特征,其他神经元分别归类为同侧偏好型(18.54%)、中间偏好型(18.54%)、全向型(3.31%)和复杂型(7.28%).多数神经元偏好的听空间区域的几何中心位于记录部位对侧听空间的中部和上部.绝大多数初级听皮层神经元对来自偏好听空间的声刺激反应的放电数较多、反应潜伏期较短,对来自非偏好听空间的声刺激反应的放电数较少、反应潜伏期较长,放电数与平均首次发放潜伏期呈显著负相关.在对声音空间信息的编码中,大脑初级听皮层可能综合放电数和潜伏期的信息以实现对声源方位的编码.

Many previous studies have shown that auditory cortical neurons are sensitive to sound spatial information, however, the mechanism of sound spatial coding is still not fully understood. Until now, detail studies on sound spatial coding have not been reported in the rat primary auditory cortex. Using electrophysiological technique, spatial response areas of 151 neurons in the rat primary auditory cortex were investigated. The relationships between spike counts and average first-spike latencies in the spatial response areas were analyzed. The results showed that, the majority （52.32%） of cortical neurons exhibited contralateral preference in the frontal auditory space whereas other neurons exhibited ipsilateral preference （18.54%） and midline preference （18.54%）, and only a few neurons were included in the category of omnidirection （3.31%） and complex （7.28%）. For the majority of cortical neurons, the arithmetic center of the preferred spatial area were distributed in the up and middle portion of the contralateral space relative to the recording side. Most neurons responded strongly to stimuli from their preferred space with shorter average first-spike latencies, and responded weakly to stimuli from non-preferred space with longer average latencies. In the spatial response area, the spike counts were negatively correlated with average first-spike latencies. The auditory cortex might use the information of both spike counts and average response time to code sound spatial information.