Herbert H, Aschoff A, Ostwald J
Department of Animal Physiology, University of Tübingen, Federal Republic of Germany.
J Comp Neurol. 1991 Feb 1;304(1):103-22. doi: 10.1002/cne.903040108.
We examined the organization of descending projections from auditory and adjacent cortical areas to the inferior colliculus (IC) in the rat by using the retrograde and anterograde transport of wheat germ agglutinin-horseradish peroxidase. Small tracer injections were placed into cytologically defined subnuclei of the IC. On the basis of the resulting pattern of retrogradely labeled neurons in the cortex, different cortical areas and fields were defined. Two secondary areas located ventrocaudally (Te2) and ventrally (Te3) to the primary auditory area (Te1) were delineated. The primary auditory area was subdivided into a posterior (Te1.p), a medial (Te1.m), and an anterior (Te1.a) auditory field. In addition, we outlined an area located rostrally to the auditory areas comprising a part of the secondary somatosensory cortex, as well as a dorsal belt surrounding dorsally the auditory areas. The following basic patterns of corticocollicular projections are revealed: 1) layers 2 and 3 of the dorsal cortex of the IC (DC2, DC3) are differentially innervated by the primary auditory fields (Te1.p and Te1.a project bilaterally to DC2, while Te1.m projects bilaterally and in topographical order to DC3); cells in Te1.m, arranged in caudal to rostral sequence, project to corresponding loci in DC3 arranged from dorsolateral to ventromedial; 2) the fibrocellular capsule of the IC, comprising layer 1 of the dorsal and external cortex of the IC, receives input from the secondary auditory area Te2; 3) layers 2 and 3 of the external cortex of the IC are only weakly innervated by the primary and secondary auditory cortex; 4) the intercollicular zone receives its major input from the secondary auditory area Te3, the secondary somatosensory cortex, and the dorsal belt; and 5) finally, the central nucleus of the IC receives no input from the temporal cortex at all. Our results demonstrate that the corticocollicular projections are highly organized. These pathways may modulate auditory processing in different functional circuits of the inferior colliculus.
我们通过使用小麦胚凝集素-辣根过氧化物酶的逆行和顺行运输，研究了大鼠听觉及相邻皮质区域至下丘（IC）的下行投射组织。将微量示踪剂注射到IC的细胞学定义亚核中。根据皮质中逆行标记神经元的结果模式，定义了不同的皮质区域和脑区。确定了位于初级听觉区（Te1）腹尾侧（Te2）和腹侧（Te3）的两个次级区域。初级听觉区被细分为后听觉区（Te1.p）、内侧听觉区（Te1.m）和前听觉区（Te1.a）。此外，我们勾勒出一个位于听觉区前方的区域，其包括部分次级躯体感觉皮质，以及一个围绕听觉区背侧的背侧带。揭示了以下皮质-下丘投射的基本模式：1）IC背侧皮质的第2层和第3层（DC2、DC3）由初级听觉区有差异地支配（Te1.p和Te1.a双侧投射至DC2，而Te1.m双侧并按拓扑顺序投射至DC3）；Te1.m中的细胞按尾侧至头侧顺序排列，投射至DC3中从背外侧至腹内侧排列的相应位点；2）IC的纤维细胞囊，包括IC背侧和外侧皮质的第1层，接受来自次级听觉区Te2的输入；3）IC外侧皮质的第2层和第3层仅由初级和次级听觉皮质微弱支配；4）下丘间区主要接受来自次级听觉区Te3、次级躯体感觉皮质和背侧带的输入；5）最后，IC的中央核完全不接受来自颞叶皮质的输入。我们的结果表明，皮质-下丘投射高度有序。这些通路可能调节下丘不同功能回路中的听觉处理。
