Luminance Changes Drive Directional Startle through a Thalamic Pathway

Lucy A.L. Heap, Gilles Vanwalleghem, Andrew W. Thompson, Itia A. Favre-Bulle, Ethan K. Scott*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

19 Citations (Scopus)


Looming visual stimuli result in escape responses that are conserved from insects to humans. Despite their importance for survival, the circuits mediating visual startle have only recently been explored in vertebrates. Here we show that the zebrafish thalamus is a luminance detector critical to visual escape. Thalamic projection neurons deliver dim-specific information to the optic tectum, and ablations of these projections disrupt normal tectal responses to looms. Without this information, larvae are less likely to escape from dark looming stimuli and lose the ability to escape away from the source of the loom. Remarkably, when paired with an isoluminant loom stimulus to the opposite eye, dimming is sufficient to increase startle probability and to reverse the direction of the escape so that it is toward the loom. We suggest that bilateral comparisons of luminance, relayed from the thalamus to the tectum, facilitate escape responses and are essential for their directionality. Animals from insects to humans escape from looming visual stimuli. With calcium imaging in larval zebrafish, we show that the thalamus detects a drop in luminance as a simulated predator approaches, directing an appropriate escape movement away from the predator.

Original languageEnglish
Pages (from-to)293-301.e4
Publication statusPublished - 25 Jul 2018
Externally publishedYes


  • calcium imaging
  • GCaMP
  • selective plane illumination microscopy
  • SPIM
  • superior colliculus
  • tectum
  • thalamus
  • vision
  • visual escape
  • zebrafish


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