Most image-forming animal eyes encode light as a function of space, time, and wavelength. “Colour vision” is associated with the latter. At its most fundamental level, decoding wavelength information in light requires combining the signals from just two spectrally distinct photoreceptors neurons. Such a basic circuit does not require sophisticated eye optics, and accordingly forms of rudimentary spectral opponency is thought to long predate image forming vision. “Colour vision” was therefore probably also already a key staple ingredient of retinal circuits when early proto-vertebrates began evolving full-blown eyes during the Cambrian. How then did vertebrate lineages and species make use of this amazing, pre-existing machinery as they diversified their many shapes and sizes of full-blown eyes that we see in essentially all vertebrates today? What are the overarching principles of animal colour vision, and, in view of the vastly diverse visual environments on earth, how general can they even be?
Comparing bulk zebrafish-brain responses to wide-field flashes of different wavelength light reveals strong On-Off biases depending on the stimulation wavelength. UV mostly elicits On-responses, blue/green mostly Off-responses, and only red light produces an approximate balance of On and Off. From Bartel et al. 2020 bioRxiv.
Related key publications
Yoshimatsu T, Bartel P, Schroeder C, Janiak FK, St-Pierre F, Berens P, Baden T$. Near-optimal rotation of colour space by zebrafish cones in vivo. (2020). bioRxiv doi: https://doi.org/10.1101/2020.10.26.356089. direct link. pdf.
Bartel P$, Janiak FK, Osorio D, Baden T$. Colourfulness as a possible measure of object proximity in the larval zebrafish brain. (2020). bioRxiv doi: https://doi.org/10.1101/2020.12.03.410241. direct link. pdf.
Zimmermann MJYbioRxiv version). d, Chagas AM, Bartel P, Pop S, Prieto Godino LL, Baden T . (2020). LED Zappelin’: An open source LED controller for arbitrary spectrum visual stimulation and optogenetics during 2-photon imaging. HardwareX e00127 (
Zimmermann MJY*, Nevala NE*, Yoshimatsu T*, Osorio D, Nilsson DE, Berens P, Baden T
Below: comparing spectral tunings of photoreceptor outputs across zebrafish (top) and fruit flies (bottom), in relation to the spectral statistics of each retina’s natural environment. From Yoshimatsu et al. 2020 bioRxiv.
Main people involved in colour vision work
Retina and brain
Colour vision at low light
Paul A Roberts
Adult zebrafish retina