Ascending spinal projections to the optic tectum, facial and vagal lobes in the goldfish, Carassius auratus

Using biotinylated dextran-amines as tracer, we observed prominent ascendin g spinal projections to three unreported areas in the gold fish brain viz. the optic tectum (OT), facial (FL) and vagal (VL) lobes. From the lateral s pinal lemniscus (LSL), some fiber tracts separated off and extended mediodo rsally, fanned out and innervated the FL. The VL was clearly laminated and showed three layers-the inner primary motor neuron and fiber layer (PMNF), outer secondary neuron layer (SN) and middle primary and secondary fiber la yer (PSF). The PMNF received maximal innervation. Besides several fibers ex tending directly into the SN from the LSL, a few fibers extended dorsolater ally from the PMNF and innervated the SN. Several ascending fibers extended into the torus semicircularis, thalamic and pretectal areas and innervated the OT. The possible functional significance of the spinal innervation of these brain areas has been discussed. (C) 1999 Elsevier Science B.V.