Lomber Stephen G, Malhotra Shveta, Hall Amee J
Centre for Brain and Mind, Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada.
Hear Res. 2007 Jul;229(1-2):31-45. doi: 10.1016/j.heares.2007.01.013. Epub 2007 Jan 17.
The purpose of this study is to: (1) examine the relative contributions of the 13 acoustically-responsive regions of the cerebral cortex to sound localization; (2) examine the laminar contributions to spatial localization behavior for each of the cortical areas identified to be critical for accurately determining the position of a sound source; and (3) synthesize the findings from sound localization studies and the underlying corticocortical and corticotectal connections to develop a processing system for sound localization information within and between the cerebral cortex and the superior colliculus. First, we examined performance on a sound localization task before, during, and after unilateral or bilateral reversible cooling deactivation of each region of acoustically-responsive cortex. Overall, unilateral deactivation of primary auditory cortex and the dorsal zone (AI/DZ), the posterior auditory field (PAF), or the auditory field of the anterior ectosylvian sulcus (AES) yielded profound sound localization deficits in the contralateral field. Bilateral deactivations of the same regions yielded bilateral sound localization deficits. Second, graded cooling of AI/DZ or PAF showed that deactivation of only the superficial layers was required to elicit sound localization deficits. However, graded cooling of AES revealed that cooling of the superficial layers alone does not cause significant sound localization deficits. Profound deficits were identified only when cooling extended through the full thickness of AES cortex. Therefore, we propose that the superficial layers of AI/DZ or PAF and the deeper layers of AES are necessary for determining the precise location of a sound source. Finally, when these results are combined with data on corticocortical and corticotectal projections, we propose that signals processed in the superficial layers of AI, DZ, or PAF feed forward to the auditory field of AES. In turn, neurons in the deeper layers of AES project to the intermediate and deeper layers of the superior colliculus. Therefore, we propose that sound localization signals processed in primary and non-primary auditory cortex are transmitted to the superior colliculus by means of the auditory field of the AES.
（1）研究大脑皮层13个听觉响应区域对声音定位的相对贡献；（2）研究对准确确定声源位置至关重要的每个皮层区域对空间定位行为的分层贡献；（3）综合声音定位研究结果以及潜在的皮质皮质和皮质顶盖连接，以开发大脑皮层与上丘内部及之间声音定位信息的处理系统。首先，我们在单侧或双侧可逆性冷却失活每个听觉响应皮层区域之前、期间和之后，检查了声音定位任务的表现。总体而言，单侧失活初级听觉皮层和背侧区（AI/DZ）、后听觉场（PAF）或前外侧沟听觉场（AES）会在对侧场产生严重的声音定位缺陷。相同区域的双侧失活会产生双侧声音定位缺陷。其次，对AI/DZ或PAF进行分级冷却表明，仅失活表层就会引发声音定位缺陷。然而，对AES进行分级冷却表明，仅冷却表层不会导致明显的声音定位缺陷。只有当冷却延伸至AES皮层的全层时，才会出现严重缺陷。因此，我们提出AI/DZ或PAF的表层以及AES的深层对于确定声源的精确位置是必要的。最后，当这些结果与皮质皮质和皮质顶盖投射的数据相结合时，我们提出在AI、DZ或PAF表层处理的信号会向前馈送到AES听觉场。反过来，AES深层的神经元投射到上丘的中层和深层。因此，我们提出在初级和非初级听觉皮层处理的声音定位信号通过AES听觉场传递至上丘。
