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Updated: Jan 26, 2026

Embryo Microinjection and Electroporation in the Chordate Ciona intestinalis
Published on: October 16, 2016
Parallel visual circuitry in a basal chordate
Matthew J Kourakis1, Cezar Borba2, Angela Zhang3
1Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, United States.
Abstract:
A common CNS architecture is observed in all chordates, from vertebrates to basal chordates like the ascidian Ciona. Ciona stands apart among chordates in having a complete larval connectome. Starting with visuomotor circuits predicted by the Ciona connectome, we used expression maps of neurotransmitter use with behavioral assays to identify two parallel visuomotor circuits that are responsive to different components of visual stimuli. The first circuit is characterized by glutamatergic photoreceptors and responds to the direction of light. These photoreceptors project to cholinergic motor neurons, via two tiers of cholinergic interneurons. The second circuit responds to changes in ambient light and mediates an escape response. This circuit uses GABAergic photoreceptors which project to GABAergic interneurons, and then to cholinergic interneurons. Our observations on the behavior of larvae either treated with a GABA receptor antagonist or carrying a mutation that eliminates photoreceptors indicate the second circuit is disinhibitory.
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