title: A novel relay nucleus between the inferior colliculus and the optic tectum in the chicken (Gallus gallus).
abstract: Processing multimodal sensory information is vital for behaving animals in many contexts. The barn owl, an auditory specialist, is a classic model for studying multisensory integration. In the barn owl, spatial auditory information is conveyed to the optic tectum (TeO) by a direct projection from the external nucleus of the inferior colliculus (ICX). In contrast, evidence of an integration of visual and auditory information in auditory generalist avian species is completely lacking. In particular, it is not known whether in auditory generalist species the ICX projects to the TeO at all. Here we use various retrograde and anterograde tracing techniques both in vivo and in vitro, intracellular fillings of neurons in vitro, and whole-cell patch recordings to characterize the connectivity between ICX and TeO in the chicken. We found that there is a direct projection from ICX to the TeO in the chicken, although this is small and only to the deeper layers (layers 13-15) of the TeO. However, we found a relay area interposed among the IC, the TeO, and the isthmic complex that receives strong synaptic input from the ICX and projects broadly upon the intermediate and deep layers of the TeO. This area is an external portion of the formatio reticularis lateralis (FRLx). In addition to the projection to the TeO, cells in FRLx send, via collaterals, descending projections through tectopontine-tectoreticular pathways. This newly described connection from the inferior colliculus to the TeO provides a solid basis for visual-auditory integration in an auditory generalist bird. J. Comp. Neurol. 525:513-534, 2017. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Lehrstuhl für Zoologie, Technische Universität München, 85354, Freising-Weihenstephan, Germany.
authors.forename: Bertram
authors.initials: B
authors.lastname: Niederleitner
authors.affiliation: Lehrstuhl für Zoologie, Technische Universität München, 85354, Freising-Weihenstephan, Germany.
authors.forename: Cristian
authors.initials: C
authors.lastname: Gutierrez-Ibanez
authors.affiliation: Lehrstuhl für Zoologie, Technische Universität München, 85354, Freising-Weihenstephan, Germany.
authors.forename: Quirin
authors.initials: Q
authors.lastname: Krabichler
authors.affiliation: Lehrstuhl für Zoologie, Technische Universität München, 85354, Freising-Weihenstephan, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Weigel
authors.affiliation: Lehrstuhl für Zoologie, Technische Universität München, 85354, Freising-Weihenstephan, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Luksch
mesh_terms: D000200:Action Potentials; D000818:Animals; D001306:Auditory Pathways / Q000033:anatomy & histology / Q000502:physiology; D002645:Chickens / Q000033:anatomy & histology* / Q000502:physiology*; D007150:Immunohistochemistry; D007245:Inferior Colliculi / Q000033:anatomy & histology* / Q000502:physiology*; D056347:Neuroanatomical Tract-Tracing Techniques; D009474:Neurons / Q000166:cytology / Q000502:physiology; D018408:Patch-Clamp Techniques; D010784:Photomicrography; D013477:Superior Colliculi / Q000033:anatomy & histology* / Q000502:physiology*; D046509:Tissue Culture Techniques
keywords: FRL; MLd; RRID:AB_10013220; RRID:AB_2109419; RRID:AB_2313571; RRID:AB_2336126; RRID:SCR_001622; biocytin; birds; midbrain; nucleus mesencephalicus lateralis pars dorsalis; slice; torus semicircularis