The avian midbrain and the tecto-isthmic circuit: Cells, Circuits, Concepts

Abstract

Event Abstract Back to Event The avian midbrain and the tecto-isthmic circuit: Cells, Circuits, Concepts Harald Luksch1* 1 Technische Universität München, Department of Animal Science, Germany The vertebrate dorsal midbrain (superior colliculus in mammals, optic tectum in all other vertebrate classes) is a central interface between sensory stimuli and behavioral motor patterns. The tectum consists of multiple laminae with specific cell types and connectivity with many similarities between vertebrate classes. The tectum receives a strong retinal projection that forms a map of visual space in the upper layers. This map acts as a master coordinate system for other sensory afferents (auditory, somatosensory etc.), leading to a multimodal representation of the sensory environment. While the size of the optic tectum is variable among vertebrates, the sensorimotor functions of the tectum appear to be conserved for all vertebrate classes. While a homologation of the midbrain across vertebrates is difficult, I will discuss a hypothesis to explain the anatomical change that occurred during mammalian evolution. With a high degree of structural order, identifiable cell types and known input and output connectivity, the analysis of the tectum with a combined experimental-computational approach can provide a mechanistic understanding of sensory computation. By integration of projections with other visual and non-visual nuclei in the brain, the basic neuronal computations can be gradually extended to generate more complex functions. Recent advances have been made in the analysis of feedback loops formed between the optic tectum and a group of nuclei in the isthmic area in several bird species. The function of these circuits is considered to be a bottom-up attentional system that identifies the most salient object and allows for both orienting movements as well as fast motor responses in, for example, escape behaviours. These functions are not restricted to visual computation, but (taking into account the tectal role as a multisensory spatial center) deals predominantly with spatial coordinates to identify potential targets through a saliency-based process. Recent electrophysiological as well as modelling studies in the chicken midbrain have suggested that a variety of mechanisms is implemented in the tecto-isthmic network, ranging from stimulus competition and attentional switching to inhibition of return and novelty preference. Most of these functions are however mechanisms that comprise the entire network and are hard to evaluate from single-cell recordings, but require the analysis of the network’s spatio-temporal activation pattern. To this end, we have taken to optical imaging of voltage-dependent dyes in a slice preparation where the tecto-isthmic network is largely intact. By mimicking sensory input with patterned electrical stimulation, we can record the network activation upon various stimulation protocols and evaluate whether the current models of tecto-isthmic circuitry are valid. Acknowledgements This work was supported by the Bernstein Center for Computational Neuroscience in Munich, Germany Keywords: feedback circuits, isthmic system, multimodal integration, tectum opticum Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster Presentation (see alternatives below as well) Topic: Sensorimotor Integration Citation: Luksch H (2012). The avian midbrain and the tecto-isthmic circuit: Cells, Circuits, Concepts. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00321 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Prof. Harald Luksch, Technische Universität München, Department of Animal Science, Freising-Weihenstephan, Bavaria, 85354, Germany, harald.luksch@wzw.tum.de Login Required This action requires you to be registered with Frontiers and logged in. 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