Binocularity in the Little Owl, <i>Athene noctua</i>

Abstract

The efferent projections from the visual thalamus to the Wulst were studied in the little owl, Athene noctua. Cells of origin were identified by retrograde labeling after injections of wheat-germ-agglutinin-conjugated horseradish peroxidase into the Wulst. The labeled-cell distribution was correlated with the distribution of anterogradely labeled retinal terminals as revealed by intraocular injections of horseradish peroxidase. The results demonstrated a bilateral thalamofugal visual pathway ascending from the nucleus dorsolateral anterior thalami (DLA). Projections from the visual thalamus to the Wulst showed a specific and orderly pattern and retrogradely labeled cells of DLA were distributed equally, in a complementary fashion, on both sides of the brain, with a small region of overlap. Retinal termination fields in DLA largely overlapped relay neurons projecting to either Wulst, although the overlap was not complete. Despite differences in the organization of avian and mammalian visual pathways, which reflect their separate evolutionary origins, similarities between the DLA in the little owl and the lateral geniculate nucleus in mammals suggest that, during evolution similar selective pressures for binocularity led to a similar morphological organization.

Multiple Visual Field Representations in the Visual Wulst of a Laterally Eyed Bird, the Zebra Finch (Taeniopygia guttata)

“…Principally, our results are congruent with those previously described by other authors (e.g. [ 22 , 41 , 42 , 43 ]) and reviewed by Güntürkün et al [ 21 ]. We here found projections to the visual wulst from the following thalamic areas: SPC (n. superficialis parvocellularis), DLAmc (n. dorsolateralis anterior, pars magnocellularis), DLLd and DLLv (n. dorsolateralis pars dorsalis/ pars ventralis), LdOPT (n. lateralis dorsalis nuclei optici principalis thalami), n. SpRt (n. suprarotundus).…”

Distribution of Prosaposin mRNA in the Central Nervous System of the Pigeon (Columba livia)

“…In evolutionary and adaptation concepts, the avian and mammalian telencephalons have similar principles of organization (Karten, ; Reiner et al., ; Karten and Shimizu, ; Butler and Hodos, ). Previous studies have compared and evaluated the avian and mammalian circuitry and pathway connections (Casini et al., ; Kitt and Brauth, ; Bagnoli et al., ; Atoji and Wild, ; Atoji et al., ), while other studies have been concerned with the comparative neurochemistry of selected telencephalic areas (Reiner et al., ; Ericshen et al., ; Shimizu et al., ). A detailed and comprehensive study of the distribution of signal molecules in the CNS of different avian species can provide further clues to the evolution and establishment of avian pattern of telencephalic organization.…”