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Curr Biol. 2015 Jul 20;25(14):1823-34. doi: 10.1016/j.cub.2015.06.002. Epub 2015 Jun 25.

A Visual Pathway for Looming-Evoked Escape in Larval Zebrafish.

Author information

1
Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany.
2
Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany; Program in Neuroscience, University of California, San Francisco, San Francisco, CA 94143, USA.
3
Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany. Electronic address: hbaier@neuro.mpg.de.

Abstract

Avoiding the strike of an approaching predator requires rapid visual detection of a looming object, followed by a directed escape maneuver. While looming-sensitive neurons have been discovered in various animal species, the relative importance of stimulus features that are extracted by the visual system is still unclear. Furthermore, the neural mechanisms that compute object approach are largely unknown. We found that a virtual looming stimulus, i.e., a dark expanding disk on a bright background, reliably evoked rapid escape movements. Related stimuli, such as dimming, receding, or bright looming objects, were substantially less effective, and angular size was a critical determinant of escape initiation. Two-photon calcium imaging in retinal ganglion cell (RGC) axons revealed three retinorecipient areas that responded robustly to looming stimuli. One of these areas, the optic tectum, is innervated by a subset of RGC axons that respond selectively to looming stimuli. Laser-induced lesions of the tectal neuropil impaired the behavior. Our findings demonstrate a visually mediated escape behavior in zebrafish larvae exposed to objects approaching on a collision course. This response is sensitive to spatiotemporal parameters of the looming stimulus. Our data indicate that a subset of RGC axons within the tectum responds selectively to features of looming stimuli and that this input is necessary for visually evoked escape.

PMID:
26119746
DOI:
10.1016/j.cub.2015.06.002
[Indexed for MEDLINE]
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