Edds-Walton Peggy L, Fay Richard R
Neuroscience Institute, Marine Biological Laboratory, Woods Hole, Mass., USA.
Brain Behav Evol. 2005;66(2):73-87. doi: 10.1159/000085928. Epub 2005 May 24.
Bimodal cells in the torus semicircularis of the toadfish respond to both directional acoustic stimuli and hydrodynamic stimuli. Our previous physiological work indicated that bimodal cells may be distributed throughout the torus semicircularis. In this study, neurobiotin was used to compare the distribution of auditory-only and bimodal sites and to assess the inputs to those sites. A brief neurobiotin injection with short survival time was used to document the recording location. In other fish, a longer injection and survival time was used at an auditory-only or a bimodal site to fill the axons of the medullary inputs. Auditory-only sites were located in the most dorsal and medial sites in nucleus centralis. Bimodal sites were identified within both nucleus centralis and nucleus ventrolateralis. The greatest number of retrogradely filled cell bodies was found in the descending octaval nucleus following injection at auditory-only recording sites in nucleus centralis. In contrast, retrogradely filled cell bodies were found in both the descending octaval nucleus and the lateral line nucleus medialis following injection at bimodal sites in nucleus centralis or nucleus ventrolateralis. Retrogradely filled cell bodies were located in the dorsal and ventral divisions of the secondary octaval population from injections at either bimodal or auditory-only sites. The secondary octaval population has been implicated in auditory processing based on previous studies of both auditory specialist and auditory generalist fishes; however, this study is the first to reveal the potential role of the secondary octaval population in directional hearing in a fish. Relatively large numbers of retrogradely filled cells around the lateral lemniscus at consistent locations in the medulla indicate that a perilemniscal cell group also might be a component of the directional hearing circuit.
蟾鱼半规管隆起中的双峰细胞对定向声刺激和水动力刺激均有反应。我们之前的生理学研究表明，双峰细胞可能分布于整个半规管隆起。在本研究中，使用神经生物素比较仅听觉位点和双峰位点的分布，并评估这些位点的输入。通过短暂注射神经生物素并缩短存活时间来记录记录位置。在其他鱼类中，在仅听觉或双峰位点使用更长的注射时间和存活时间来填充延髓输入的轴突。仅听觉位点位于中央核最背侧和内侧的位置。在中央核和外侧腹核中均鉴定出双峰位点。在中央核仅听觉记录位点注射后，在下行八分体核中发现逆行填充的细胞体数量最多。相比之下，在中央核或外侧腹核的双峰位点注射后，在下行八分体核和内侧侧线核中均发现逆行填充的细胞体。在双峰或仅听觉位点注射后，逆行填充的细胞体位于次级八分体群的背侧和腹侧部分。根据之前对听觉特化鱼类和听觉泛化鱼类的研究，次级八分体群与听觉处理有关；然而，本研究首次揭示了次级八分体群在鱼类定向听觉中的潜在作用。延髓中一致位置的外侧丘系周围相对大量的逆行填充细胞表明，外侧丘系周围细胞群也可能是定向听觉回路的一个组成部分。
