Connections of Octaval and Lateral Line Nuclei of the Medulla in the Goldfish, Including the Cytoarchitecture of the Secondary Octaval Population in Goldfish and Catfish

Abstract

Cytoarchitectural analyses combined with injections of the tracer horseradish peroxidase in various structures in the brain of the goldfish, Carassius auratus, have defined some of the major components of acoustic and lateral line mechanosensory circuits between the medulla and midbrain. The main acoustic receptor in Carassius, the saccule, is known to provide a major input to the dorsomedial zone of the descending octaval nucleus. The dorsomedial zone in turn projects bilaterally to the secondary octaval population (SO) and to nucleus centralis of the torus semicircularis. The SO is composed of three major subdivisions which are also present in a related otophysan, the catfish Ictalurus punctatus. The SO in Carassius projects bilaterally to nucleus centralis and to the saccular recipient zones of the ipsilateral descending octaval nucleus. By contrast, the mechanosensory lateral line receptors are known to direct most of their input to nucleus medialis. Nucleus medialis in turn projects bilaterally to nucleus praeeminentialis, nucleus ventrolateralis of the torus semicircularis, and the optic tectum, and to the contralateral nucleus medialis. We also provide evidence for a bilateral projection of nucleus medialis to the sensory trigeminal nucleus, and for a reciprocal input from the sensory trigeminal nucleus to the ipsilateral nucleus medialis.

Visualization of two distinct classes of neurons by gad2 and zic1 promoter/enhancer elements in the dorsal hindbrain of developing zebrafish reveals neuronal connectivity related to the auditory and lateral line systems

“…Thus, we suggest that the neurons (in the AON, DON, and/or MON) projecting to the TS originate mainly from r2 to r6. However, another lateral line-related nucleus, the caudal octavolateral nucleus, does not provide projections to the TS in bowfin and goldfish (McCormick, 1989;McCormick and Hernandez, 1996) and is expected to be located caudally to the MON. The origin of lateral line-related nuclei might, therefore, extend more caudally than r6.…”

“…The bHLH factor Atoh1a is specifically required for development of the zn-5(ϩ)Lhx2/9(ϩ) neurons but not for development of the Gad1/2(ϩ) neurons. In adult goldfish (right), the ascending projection neurons (yellow, filled oval and solid line) in the medial octavolateral nucleus (MON) provide lateral line information to the lateral region of the midbrain TS (yellow; McCormick and Hernandez, 1996;New et al, 1996). There is also a projection to the contralateral MON (yellow, open oval and dotted line; New et al, 1996).…”

“…It is unknown whether distinct neuronal populations project separately to the TS or contralateral MON, or the same neuronal population projects to both the TS and contralateral MON (New et al, 1996). The ascending projection neurons (blue, filled oval and solid line) in the descending octaval nucleus (DON) provide auditory information to the medial region of the TS (blue) in goldfish (McCormick and Hernandez, 1996;Yamamoto and Ito, 2005). Similarly to the MON, there is also a projection to the contralateral DON (blue, open oval and dotted line; Yamamoto and Ito, 2005).…”

“…In other fish species such as carp and catfish, the anterior octaval nucleus (AON) also provides auditory information to the medial region of the TS (Echteler, 1984;Yamamoto and Ito, 2005). In goldfish, this nucleus seems to provide few, if any, projections to the TS (McCormick and Hernandez, 1996;Yamamoto and Ito, 2005). UAS, upstream activating sequences.…”

Temporal Coding of Concurrent Acoustic Signals in Auditory Midbrain

“…2 A,MO) . These nuclei in turn project to a variety of nuclei, including a nucleus centralis in the torus semicircularis of the midbrain (Knudsen, 1977;Bass et al, 1996;McCormick and Hernandez, 1996), a homolog of the mammalian inferior colliculus (McCormick, 1992). Recordings were made from the nucleus centralis ( Fig.…”