Schofield Brett R, Coomes Diana L
Department of Neurobiology, Northeastern Ohio Universities College of Medicine, 4209 State Route 44, P.O. Box 95, Rootstown, OH 44272, USA.
Hear Res. 2006 Jun-Jul;216-217:81-9. doi: 10.1016/j.heares.2006.01.004.
The inferior colliculus (IC) and superior olivary complex (SOC) are important sources of descending pathways to the cochlear nucleus. The IC and SOC are also targets of direct projections from the auditory cortex but it is not known if cortical axons contact the cells that project to the cochlear nucleus. Multi-labeling techniques were used to address this question in guinea pigs. A fluorescent anterograde tracer was injected into temporal cortex to label corticofugal axons. Different fluorescent tracers were injected into one or both cochlear nuclei to label olivary and collicular cells. The brain was subsequently processed for fluorescence microscopy and the IC and SOC were examined for apparent contacts between cortical axons and retrogradely labeled cells. The results suggest that cortical axons contact cochlear nucleus-projecting cells in both IC and SOC. In both regions, contacts were more numerous on the side ipsilateral to the injected cortex. In the IC, the contacted cells projected ipsilaterally or contralaterally to the CN. In the SOC, the contacted cells projected ipsilaterally, contralaterally or bilaterally to the CN. We conclude that auditory cortex is in a position to modulate descending pathways from both the IC and SOC to the cochlear nucleus.
下丘（IC）和上橄榄复合体（SOC）是通向耳蜗核的下行通路的重要来源。IC和SOC也是听觉皮层直接投射的目标，但尚不清楚皮层轴突是否与投射到耳蜗核的细胞接触。在豚鼠中使用多标记技术来解决这个问题。将荧光顺行示踪剂注入颞叶皮层以标记皮质离心轴突。将不同的荧光示踪剂注入一个或两个耳蜗核以标记橄榄核和下丘细胞。随后对大脑进行荧光显微镜处理，并检查IC和SOC中皮层轴突与逆行标记细胞之间的明显接触。结果表明，皮层轴突与IC和SOC中投射到耳蜗核的细胞接触。在这两个区域中，与注射皮层同侧的一侧接触更多。在IC中，被接触的细胞向耳蜗核同侧或对侧投射。在SOC中，被接触的细胞向耳蜗核同侧、对侧或双侧投射。我们得出结论，听觉皮层能够调节从IC和SOC到耳蜗核的下行通路。
