Rodriguez-Nodal F, Bajo-Lorenzana V M
Department of Physiology, University of Oxford, Oxford, UK.
Rev Neurol. 2012 Jul 16;55(2):91-100.
Sound localization is a computational process accomplished along the auditory pathway. Once the acoustic information received at each ear is analyzed independently (monaural cues) and comparatively (binaural cues), those cues are integrated to generate a coherent spatial percept. Using adult ferrets trained by positive conditioning in a spatial task, we aimed to study the role of the auditory cortex in the ability to localize sounds under both normal hearing and monaurally occluded conditions, the latter of which requires a reinterpretation of the values of the localization cues. Sound localization deficits were found after lesion or inactivation of the different auditory cortical regions, thereby indicating their participation in spatial processing. The differential impairments found in the approach-to-target and in the head movement responses reveal the complex relationship between cortex and midbrain which are putatively responsible for the voluntary and reflexive aspects of localization behaviour respectively. Furthermore, every auditory cortical region contributes to the adaptation process that follows monaural occlusion, indicating the key role that the auditory cortex plays in experience-dependent plasticity. Also, the selective lesion of the descending projections from the auditory cortex to the inferior colliculus by chromophore-targeted laser photolysis has revealed the essential function that descending pathways play in learning-induced localization plasticity.
声音定位是一个沿着听觉通路完成的计算过程。一旦每只耳朵接收到的声学信息被独立分析（单耳线索）和比较分析（双耳线索），这些线索就会被整合起来，以产生连贯的空间感知。我们利用在空间任务中通过正性条件训练的成年雪貂，旨在研究听觉皮层在正常听力和单耳闭塞条件下对声音进行定位的能力中所起的作用，在单耳闭塞条件下，需要重新解释定位线索的值。在不同听觉皮层区域发生损伤或失活后，发现了声音定位缺陷，从而表明它们参与了空间处理。在接近目标和头部运动反应中发现的不同损伤揭示了皮层和中脑之间的复杂关系，它们分别被认为是定位行为的自主和反射方面的原因。此外，每个听觉皮层区域都有助于单耳闭塞后的适应过程，这表明听觉皮层在依赖经验的可塑性中起着关键作用。同样，通过发色团靶向激光光解对从听觉皮层到下丘的下行投射进行选择性损伤，揭示了下行通路在学习诱导的定位可塑性中所起的重要作用。
