McAlpine David
Department of Physiology and The Ear Institute, University College London, Gower Street, London WC1E 6BT, UK.
J Physiol. 2005 Jul 1;566(Pt 1):21-8. doi: 10.1113/jphysiol.2005.083113. Epub 2005 Mar 10.
Determining the location of a sound source requires the use of binaural hearing--information about a sound at the two ears converges onto neurones in the auditory brainstem to create a binaural representation. The main binaural cue used by many mammals to locate a sound source is the interaural time difference, or ITD. For over 50 years a single model has dominated thinking on how ITDs are processed. The Jeffress model consists of an array of coincidence detectors--binaural neurones that respond maximally to simultaneous input from each ear--innervated by a series of delay lines--axons of varying length from the two ears. The purpose of this arrangement is to create a topographic map of ITD, and hence spatial position in the horizontal plane, from the relative timing of a sound at the two ears. This model appears to be realized in the brain of the barn owl, an auditory specialist, and has been assumed to hold for mammals also. Recent investigations, however, indicate that both the means by which neural tuning for preferred ITD, and the coding strategy used by mammals to determine the location of a sound source, may be very different to barn owls and to the model proposed by Jeffress.
确定声源的位置需要利用双耳听觉——两只耳朵接收到的声音信息会汇聚到听觉脑干中的神经元上，从而形成一种双耳表征。许多哺乳动物用来定位声源的主要双耳线索是双耳时间差，即ITD。五十多年来，关于ITD如何被处理，一直有一个单一模型主导着人们的思考。杰弗里斯模型由一系列重合探测器组成——双耳神经元，它们对来自每只耳朵的同步输入反应最大——由一系列延迟线支配，即来自两只耳朵的不同长度的轴突。这种排列的目的是根据声音在两只耳朵处的相对时间，创建ITD的地形图，进而确定水平面上的空间位置。这种模型似乎在听觉专家仓鸮的大脑中得以实现，并且一直被认为也适用于哺乳动物。然而，最近的研究表明，哺乳动物用于偏好ITD的神经调谐方式以及用于确定声源位置的编码策略，可能与仓鸮以及杰弗里斯提出的模型有很大不同。
