Tractus Septomesencephalicus

Induction of FLI cells was observed throughout the rostral to caudal extent of the preoptic region of males from the level of the Tractus septomesencephalicus to the level of the anterior commissure, and in the rostral part of the hypothalamus to the level of the supraoptic decussation.  

When a deposit of the anterograde tracer was centered in HA, efferent fibers were seen to extend mainly in three directions: 1) medially to the Tractus septomesencephalicus, which sends projections to extratelencephalic visual nuclei: 2) ventrolaterally to the lateral portion of the neostriatum frontale, where there were also labeled cells after the retrograde tracer was injected in HA; and 3) ventromedially to the paleostriatal complex, which is the avian equivalent of the mammalian caudale, 5) neostriatum intermedium, 6) archistriatum intermedium, and 7) hyperstriatum laterale. No anterogradely labeled fibers were seen in the Tractus septomesencephalicus following the tracer injections in HIS/HD. In addition, HA is the source of an extratelencephalic projection via the Tractus septomesencephalicus.  

We also observed an intensely stained area ventral to the fasciculus prosencephali lateralis and lateral to the Tractus septomesencephalicus, a weakly to moderately stained band ventral to the lobus parolfactorius, an intensely stained zone along the lateral ventricle in the hyperstriatum ventrale, and an unstained almond-shaped nucleus in the lateral hyperstriatum ventrale.  

ir-cGnRH I cells were located: along the medial aspect of the ventriculus lateralis, nucleus accumbens, and bed nucleus of the stria terminalis; ventral to the Tractus septomesencephalicus and extending medially to the third ventricle, and caudally into the lateral hypothalamic area; and in a diffuse band extending from the nucleus preopticus medialis to the nucleus dorsomedialis anterior thalami.  

APd was the smallest nucleus among the pretectal nuclei lying just above the Tractus septomesencephalicus (SMT) and received the heaviest retinal inputs.  

The data showed ipsilateral projections from the visual Wulst and via the Tractus septomesencephalicus upon the dorsal thalamus (n.: dorsolateralis anterior superficialis parvocellularis), ventral thalamus (n.: intercalatus, ventrolateralis, geniculatus lateralis pars ventralis--GLv), pretectum (n.: superficialis synencephali, geniculatus pretectalis, griseus tectalis, pretectalis: diffusus, pars lateralis and pars medialis, area pretectalis) as well as to the nucleus of the basal optic root, n.  

Following horseradish peroxidase injections into the pigeon Tractus septomesencephalicus, the efferent outflow bundle of the avian Wulst, retrogradely labeled neurons within the Wulst were confined to the superficialmost layer, the hyperstriatum accessorium.  

Electrolytic lesions were placed in the Tractus septomesencephalicus (TSM) and tractus occipitomesencephalicus (TOM), efferent pathways originating in visual and somatosensorimotor areas of the avian telencephalon and distributing widely to brain stem and spinal nuclear regions.  

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