Laboratory of Auditory Neuroscience, Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, D-20246 Hamburg, Germany.
Cereb Cortex. 2010 Feb;20(2):492-506. doi: 10.1093/cercor/bhp222. Epub 2009 Nov 11.
Binaural cues are required for localization of sound sources. In the present paper, representation of binaural cues has been investigated in the adult auditory cortex. Hearing and congenitally deaf cats were stimulated through binaural cochlear implants and unit responses were collected in the subregion of field A1 showing the largest amplitudes of evoked local field potentials. Sensitivity to interaural time difference (ITD) in the range from -600 to 600 micros was tested at intensities of 0-10 dB above hearing threshold. Template ITD functions were fitted to the data and parameters of ITD functions were compared between deaf and hearing animals. In deaf animals, fewer units responded to binaural stimulation, and those that responded had smaller maximal evoked firing rate. The fit to the template ITD functions was significantly worse in deaf animals, and the modulation depth in ITD functions was smaller, demonstrating a decrease in ITD sensitivity. With increasing binaural levels, hearing controls demonstrated systematic changes in ITD functions not found in deaf animals. Bimodal responses, likely related to precedence effect, were rare in deaf animals. The data demonstrate that despite some rudimentary sensitivity to interaural timing, cortical representation of ITDs is substantially altered by congenital auditory deprivation.
双耳线索对于声源定位是必需的。在本文中，我们研究了成年听觉皮层中双耳线索的表示。通过双耳耳蜗植入物刺激听力正常和先天性耳聋的猫，并在显示诱发电场电位幅度最大的 A1 区域的子区域中收集单元反应。在 0-10dB 超过听力阈值的强度下，测试了 600 微秒范围内的互差时间（ITD）敏感性。将模板 ITD 函数拟合到数据中，并比较耳聋和听力动物的 ITD 函数参数。在耳聋动物中，响应双耳刺激的单元更少，并且那些有反应的单元的最大诱发放电率更小。在耳聋动物中，对模板 ITD 函数的拟合明显更差，ITD 函数的调制深度更小，表明 ITD 敏感性降低。随着双耳水平的增加，听力对照组的 ITD 函数发生了系统变化，而耳聋动物则没有。双模态反应，可能与优先效应有关，在耳聋动物中很少见。这些数据表明，尽管对双耳时间具有一些基本的敏感性，但先天性听觉剥夺会显著改变 ITD 的皮质表示。
