High-speed optogenetic circuit mapping

George J. Augustine; Susu Chen; Harin Gill; Malvika Katarya; Jinsook Kim; John Kudolo; Li Ming Lee; Hyunjeong Lee; Shun Qiang Lo; Ryuichi Nakajima; Min-Yoon Park; Gregory Tan; Yanxia Tang; Peggy Teo; Sachiko Tsuda; Lei Wen; Su-In Yoon

doi:10.1117/12.2012404

8 March 2013 High-speed optogenetic circuit mapping

George J. Augustine, Susu Chen, Harin Gill, Malvika Katarya, Jinsook Kim, John Kudolo, Li Ming Lee, Hyunjeong Lee, Shun Qiang Lo, Ryuichi Nakajima, Min-Yoon Park, Gregory Tan, Yanxia Tang, Peggy Teo, Sachiko Tsuda, Lei Wen, Su-In Yoon

Author Affiliations +

Proceedings Volume 8586, Optogenetics: Optical Methods for Cellular Control; 858603 (2013) https://doi.org/10.1117/12.2012404
Event: SPIE BiOS, 2013, San Francisco, California, United States

Abstract

Scanning small spots of laser light allows mapping of synaptic circuits in brain slices from transgenic mice expressing channelrhodopsin-2 (ChR2). These light spots photostimulate presynaptic neurons expressing ChR2, while postsynaptic responses can be monitored in neurons that do not express ChR2. Correlating the location of the light spot with the amplitude of the postsynaptic response elicited at that location yields maps of the spatial organization of the synaptic circuits. This approach yields maps within minutes, which is several orders of magnitude faster than can be achieved with conventional paired electrophysiological methods. We have applied this high-speed technique to map local circuits in many brain regions. In cerebral cortex, we observed that maps of excitatory inputs to pyramidal cells were qualitatively different from those measured for interneurons within the same layers of the cortex. In cerebellum, we have used this approach to quantify the convergence of molecular layer interneurons on to Purkinje cells. The number of converging interneurons is reduced by treatment with gap junction blockers, indicating that electrical synapses between interneurons contribute substantially to the spatial convergence. Remarkably, gap junction blockers affect convergence in sagittal cerebellar slices but not in coronal slices, indicating sagittal polarization of electrical coupling between interneurons. By measuring limb movement or other forms of behavioral output, this approach also can be used in vivo to map brain circuits non-invasively. In summary, ChR2-mediated high-speed mapping promises to revolutionize our understanding of brain circuitry.

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George J. Augustine, Susu Chen, Harin Gill, Malvika Katarya, Jinsook Kim, John Kudolo, Li Ming Lee, Hyunjeong Lee, Shun Qiang Lo, Ryuichi Nakajima, Min-Yoon Park, Gregory Tan, Yanxia Tang, Peggy Teo, Sachiko Tsuda, Lei Wen, and Su-In Yoon "High-speed optogenetic circuit mapping", Proc. SPIE 8586, Optogenetics: Optical Methods for Cellular Control, 858603 (8 March 2013); https://doi.org/10.1117/12.2012404

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