Senatorov V V, Hu B
Loeb Health Research Institute, Ottawa Hospital/University of Ottawa, 1053 Carling Avenue, Ottawa, ON, Canada K1Y 4E9.
Neuroscience. 2002;115(1):243-50. doi: 10.1016/s0306-4522(02)00316-0.
Feedback controlling is an important element in the sensory processing in the auditory system. It has been long recognized that the inferior colliculus (IC) sends direct ascending projections to the medial geniculate body (MGB), but receives feedback regulation from the auditory cortex. In the present study we probed the shorter extracortical projections to the IC, including the direct descending pathway from the MGB. In the rat, the fluorescence retrograde tracers Fluorogold, True Blue or Rhodamine latex microspheres were injected into the IC, and the auditory thalamus and surrounding regions were examined for fluorescent neurones. We did not find any retrograde labelling in the ventral division of the MGB. However, retrogradely labelled neurones were found in the medial and suprageniculate nuclei of the MGB. We also observed densely packed groups of fluorescent neurones in the peripeduncular nucleus and numerous labelled neurones in the nucleus of the brachium of the IC. The existence of a direct descending pathway to the IC from at least some auditory thalamic nuclei challenges the perception of the colliculo-thalamic relationship as one-way traffic and suggests more direct involvement of the auditory thalamus in the feedback regulation of the incoming acoustic signals.
反馈控制是听觉系统感觉处理中的一个重要因素。长期以来人们已经认识到，下丘（IC）向内侧膝状体（MGB）发出直接的上行投射，但接受来自听觉皮层的反馈调节。在本研究中，我们探究了到下丘的较短的皮质外投射，包括从内侧膝状体发出的直接下行通路。在大鼠中，将荧光逆行示踪剂氟金、真蓝或罗丹明乳胶微球注入下丘，并检查听觉丘脑及周围区域的荧光神经元。我们在内侧膝状体的腹侧部未发现任何逆行标记。然而，在内侧膝状体的内侧核和上膝状核中发现了逆行标记的神经元。我们还在脚周核中观察到密集的荧光神经元群，并在下丘臂核中发现了许多标记的神经元。至少一些听觉丘脑核到下丘的直接下行通路的存在，挑战了将丘-丘脑关系视为单向交通的观念，并表明听觉丘脑更直接地参与了对传入声音信号的反馈调节。
