Calford M B, Aitkin L M
J Neurosci. 1983 Nov;3(11):2365-80. doi: 10.1523/JNEUROSCI.03-11-02365.1983.
The sources of ascending input to the medial geniculate body (MGB) of the cat were studied using the retrograde transport of horseradish peroxidase (HRP). HRP injections were made iontophoretically through micropipettes which were also used to record physiological properties at the injection sites. This technique produced small injections which appeared to be restricted to single subnuclei. The tectothalamic projection of the auditory system was found to consist of at least four distinct and separate pathways. The ventral division of the MGB receives a topographical projection from the central nucleus of the inferior colliculus (ICC) which preserves tonotopicity and provides short latency, sharply frequency-tuned responses. The medial part of the ICC projects to the deep dorsal nucleus, which contains only units tuned to high frequencies. The major inputs to the caudodorsal nucleus (DC) stem from nucleus sagulum and the pericentral nucleus of the inferior colliculus (ICP). Units in DC and the ventrolateral nucleus, which also receive input from ICP, have very broad tuning properties and late, habituating responses. Injections of HRP into the medial division (MGM) produced labeled cells scattered throughout the external nucleus of the inferior colliculus and the ventral part of ICC. This widespread input is reflected in the wide range of auditory responses found in MGM. Auditory responses in the suprageniculate nucleus were poorly defined and many units did not respond to tonal stimuli; following HRP injections no filled cells were found in the inferior colliculus, but labeled cells were found in the deeper layers of the superior colliculus and in the interstitial nucleus of the brachium of the inferior colliculus. Together with recent findings on the auditory thalamocortical projection, these results provide evidence for multiple parallel auditory pathways through the thalamus.
利用辣根过氧化物酶（HRP）的逆行运输法，研究了猫内侧膝状体（MGB）的上行输入源。通过微吸管进行离子电渗法注射HRP，这些微吸管还用于记录注射部位的生理特性。该技术产生的小注射似乎局限于单个亚核。发现听觉系统的顶盖丘脑投射至少由四条不同且分开的通路组成。MGB的腹侧部接受来自下丘中央核（ICC）的拓扑投射，该投射保留了音频定位，并提供短潜伏期、频率调谐尖锐的反应。ICC的内侧部分投射到深背核，该核仅包含调谐到高频的单位。尾背核（DC）的主要输入来自下丘的矢状核和中央周核（ICP）。DC和腹外侧核中的单位也从ICP接收输入，具有非常广泛的调谐特性和晚期的、习惯性的反应。将HRP注射到内侧部（MGM）中，产生的标记细胞散布在下丘的外侧核和ICC的腹侧部分。这种广泛的输入反映在MGM中发现的广泛听觉反应中。上膝状核中的听觉反应定义不明确，许多单位对音调刺激无反应；注射HRP后，在下丘中未发现填充细胞，但在上丘的深层和下丘臂的间质核中发现了标记细胞。与最近关于听觉丘脑皮质投射的发现一起，这些结果为通过丘脑的多条平行听觉通路提供了证据。
