Miller G L, Knudsen E I
Department of Neurobiology, Stanford University School of Medicine, Stanford, California 94305, USA.
J Neurophysiol. 2001 May;85(5):2184-94. doi: 10.1152/jn.2001.85.5.2184.
Binaural acoustic cues such as interaural time and level differences (ITDs and ILDs) are used by many species to determine the locations of sound sources. The relationship between cue values and locations in space is frequency dependent and varies from individual to individual. In the current study, we tested the capacity of neurons in the forebrain localization pathway of the barn owl to adjust their tuning for binaural cues in a frequency-dependent manner in response to auditory experience. Auditory experience was altered by raising young owls with a passive acoustic filtering device that caused frequency-dependent changes in ITD and ILD. Extracellular recordings were made in normal and device-reared owls to characterize frequency-specific ITD and ILD tuning in the auditory archistriatum (AAr), an output structure of the forebrain localization pathway. In device-reared owls, individual sites in the AAr exhibited highly abnormal, frequency-dependent variations in ITD tuning, and across the population of sampled sites, there were frequency-dependent shifts in the representation of ITD. These changes were in a direction that compensated for the acoustic effects of the device on ITD and therefore tended to restore a normal representation of auditory space. Although ILD tuning was degraded relative to normal at many sites in the AAr of device-reared owls, the representation of frequency-specific ILDs across the population of sampled sites was shifted in the adaptive direction. These results demonstrate that early auditory experience shapes the representation of binaural cues in the forebrain localization pathway in an adaptive, frequency-dependent manner.
诸如双耳时间差和强度差（ITD和ILD）等双耳声学线索被许多物种用于确定声源的位置。线索值与空间位置之间的关系取决于频率，并且个体之间存在差异。在当前的研究中，我们测试了仓鸮前脑定位通路中的神经元根据听觉经验以频率依赖的方式调整其对双耳线索调谐的能力。通过使用被动声学滤波装置饲养幼鸮来改变听觉经验，该装置会导致ITD和ILD发生频率依赖性变化。在正常饲养和使用装置饲养的仓鸮中进行细胞外记录，以表征听觉古纹状体（AAr）中频率特异性的ITD和ILD调谐，AAr是前脑定位通路的一个输出结构。在使用装置饲养的仓鸮中，AAr中的各个位点在ITD调谐方面表现出高度异常的、频率依赖性的变化，并且在整个采样位点群体中，ITD的表征存在频率依赖性的偏移。这些变化的方向补偿了装置对ITD的声学影响，因此倾向于恢复听觉空间的正常表征。尽管在使用装置饲养的仓鸮的AAr中，许多位点的ILD调谐相对于正常情况有所退化，但在整个采样位点群体中，频率特异性ILD的表征朝着适应性方向偏移。这些结果表明，早期听觉经验以适应性的、频率依赖的方式塑造了前脑定位通路中双耳线索的表征。
