ZFIN ID: ZDB-PUB-200603-16
The zebrafish visual system transmits dimming information via multiple segregated pathways
Robles, E., Fields, N.P., Baier, H.
Date: 2020
Source: The Journal of comparative neurology   529(3): 539-552 (Journal)
Registered Authors: Baier, Herwig
Keywords: OFF pathway, RRID:ZFIN_ZDB-ALT-090116-2, RRID:ZFIN_ZDB-ALT-090715-16, RRID:ZFIN_ZDB-GENO-140811-5, dimming, functional imaging, larval visual motor response, multiphoton
MeSH Terms: none
PubMed: 32484919 Full text @ J. Comp. Neurol.
Vertebrate retinas contain circuits specialized to encode light level decrements. This information is transmitted to the brain by dimming-sensitive OFF retinal ganglion cells (OFF-RGCs) that respond to light decrements with increased firing. It is known that OFF-RGCs with distinct photosensitivity profiles form parallel visual channels to the vertebrate brain, yet how these channels are processed by first- and higher-order brain areas has not been well characterized in any species. To address this question in the larval zebrafish visual system we examined the visual response properties of a genetically identified population of tectal neurons with a defined axonal projection to a second order visual area: id2b:gal4-positive torus longitudinalis projection neurons (TLPNs). TLPNs responded consistently to whole-field dimming stimuli and exhibited the strongest responses when dimming was preceded by low light levels. Functional characterization of OFF-RGC terminals in tectum revealed responses that varied in their photosensitivities: 1) low sensitivity OFF-RGCs that selectively respond to large light decrements, 2) high sensitivity OFF-RGCs that selectively encode small decrements, and 3) broad sensitivity OFF-RGCs that respond to a wide range of light decrements. Diverse photosensitivity profiles were also observed using pan-neuronal calcium imaging to identify dimming-responsive neurons in both tectum and torus longitudinalis. Together these data support a model in which parallel OFF channels generated in the retina remain segregated across three stages of visual processing. Segregated OFF channels with different sensitivities may allow specific aspects of dimming-evoked behaviors to be modulated by ambient light levels. This article is protected by copyright. All rights reserved.