Palmer A R, Hall D A, Sumner C, Barrett D J K, Jones S, Nakamoto K, Moore D R
MRC Institute of Hearing Research, University Park, Nottingham, UK.
Hear Res. 2007 Jul;229(1-2):148-57. doi: 10.1016/j.heares.2006.12.007. Epub 2006 Dec 16.
Our knowledge of the function of the auditory nervous system is based upon a wealth of data obtained, for the most part, in anaesthetised animals. More recently, it has been generally acknowledged that factors such as attention profoundly modulate the activity of sensory systems and this can take place at many levels of processing. Imaging studies, in particular, have revealed the greater activation of auditory areas and areas outside of sensory processing areas when attending to a stimulus. We present here a brief review of the consequences of such non-passive listening and go on to describe some of the experiments we are conducting to investigate them. In imaging studies, using fMRI, we can demonstrate the activation of attention networks that are non-specific to the sensory modality as well as greater and different activation of the areas of the supra-temporal plane that includes primary and secondary auditory areas. The profuse descending connections of the auditory system seem likely to be part of the mechanisms subserving attention to sound. These are generally thought to be largely inactivated by anaesthesia. However, we have been able to demonstrate that even in an anaesthetised preparation, removing the descending control from the cortex leads to quite profound changes in the temporal patterns of activation by sounds in thalamus and inferior colliculus. Some of these effects seem to be specific to the ear of stimulation and affect interaural processing. To bridge these observations we are developing an awake behaving preparation involving freely moving animals in which it will be possible to investigate the effects of consciousness (by contrasting awake and anaesthetized), passive and active listening.
我们对听觉神经系统功能的认识，大多基于在麻醉动物身上获取的大量数据。最近，人们普遍认识到，诸如注意力等因素会深刻调节感觉系统的活动，而且这种调节可发生在多个处理层面。尤其是成像研究表明，在关注某一刺激时，听觉区域以及感觉处理区域之外的区域会有更强的激活。在此，我们简要回顾一下这种非被动聆听的后果，并继续描述我们正在进行的一些用以研究这些后果的实验。在使用功能磁共振成像（fMRI）的成像研究中，我们能够证明注意力网络的激活，这些网络对感觉模态不具有特异性，同时还能证明颞上平面区域（包括初级和次级听觉区域）有更强且不同的激活。听觉系统丰富的下行连接似乎很可能是服务于对声音注意力的机制的一部分。一般认为这些连接在很大程度上会被麻醉所抑制。然而，我们已经能够证明，即使在麻醉状态下的标本中，去除来自皮层的下行控制也会导致丘脑和下丘中声音激活的时间模式发生相当深刻 的变化。其中一些效应似乎对受刺激的耳朵具有特异性，并会影响双耳处理。为了弥合这些观察结果，我们正在开发一种涉及自由活动动物的清醒行为标本，在其中将能够研究意识（通过对比清醒和麻醉状态）、被动聆听和主动聆听的影响。
