PROJECTIONS FROM THE ACCESSORY OPTIC-SYSTEM AND PRETECTUM TO THE DORSOLATERAL THALAMUS IN THE PIGEON (COLUMBIA-LIVIA) - A STUDY USING BOTH ANTEROGRADE AND RETROGRADE TRACERS

In birds, optic flow is analyzed by two retinal-recipient nuclei: the nucleus of the basal optic root (nBOR) of the accessory optic system ( AOS), and the pretectal nucleus, lentiformis mesencephali (LM). Previo us anatomical studies have shown that both of these nuclei have descen ding projections to structures involved in oculomotor, head movement, and postural control. In this report, using biotinylated dextran amine (BDA) and cholera toxin subunit B (CTB) for anterograde and retrograd e labelling, respectively, we investigated projections from the nBOR a nd LM to the dorsal thalamus. After injections of BDA into the nBOR an d LM, terminals were consistently found in the nucleus dorsolateralis anterior pars lateralis and pars medialis, and the nucleus dorsalis in termedius ventralis anterior of the thalamus. Some terminals were also found in the nucleus dorsolateralis anterior, nucleus dorsomedialis a nterior pars magnocellularis, nucleus dorsolateralis posterior, nucleu s superficialis parvocellularis, and the ventrointermediate area. Inje ctions of CTB into the dorsal thalamus resulted in retrogradely labell ed cells in the pretectal region, including LM. Numerous cells were al so seen in the nBOR pars lateralis and pars dorsalis, but fewer were s een in the nBOR proper. We suggest that the AOS is providing input to a thalamotelencephalic system that may be involved in several function s including: (1) multi-sensory analysis of self-motion, (2) perception of self-motion, (3) perception of the three-dimensional layout of the environment, (4) distinguishing object-motion from self-motion, and ( 5) spatial cognition. (C) 1998 Wiley-Liss, Inc.