The Journal of Neuroscience, May 1, 2003, 23(9):3726
Visuomotor Behaviors in Larval Zebrafish after GFP-Guided
Laser Ablation of the Optic Tectum
Tobias
Roeser and
Herwig
Baier
Department of Physiology and Programs in Neuroscience, Genetics,
Developmental Biology, and Human Genetics, University of California at
San Francisco, San Francisco, California 94143
The optic tectum is the largest visual center in most vertebrates
and the main target for retinal ganglion cells (RGCs) conveying visual
information from the eye to the brain. The retinotectal projection has
served as an important model in many areas of developmental neuroscience. However, knowledge of the function of the tectum is limited. We began to address this issue using laser ablations and
subsequent behavioral testing in zebrafish. We used a transgenic zebrafish line that expresses green-fluorescent protein in RGCs projecting to the tectum. By aiming a laser beam at the labeled retinal
fibers demarcating the tectal neuropil, the larval tectum could be
selectively destroyed. We tested whether tectum-ablated zebrafish
larvae, when presented with large-field movements in their
surroundings, displayed optokinetic responses (OKR) or optomotor responses (OMR), two distinct visuomotor behaviors that compensate for
self-motion. Neither OKR nor OMR were found to be dependent on intact
retinotectal connections. Also, visual acuity remained unaffected.
Tectum ablation, however, slowed down the OKR by reducing the frequency
of saccades but left tracking velocity, gain, and saccade amplitude
unaffected. Removal of the tectum had no effect on the processing of
second-order motion, to which zebrafish show both OKR and OMR,
suggesting that the tectum is not an integral part of the circuit that
extracts higher-order cues in the motion pathway.
Key words:
visual system; vision; retina; optomotor; optokinetic; behavior; retinal ganglion cell; tectum; superior
colliculus; zebrafish; Danio rerio; transgenic; GFP; sonic hedgehog; laser ablation
Copyright © 2003 Society for Neuroscience 0270-6474/03/2393726-09$05.00/0
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