Synaptic connectivity to L2/3 of primary visual cortex measured by two-photon optogenetic stimulation
- Allen Institute for Brain Science, United States
Abstract
Understanding cortical microcircuits requires thorough measurement of physiological properties of synaptic connections formed within and between diverse subclasses of neurons. Towards this goal, we combined spatially precise optogenetic stimulation with multicellular recording to deeply characterize intralaminar and translaminar monosynaptic connections to supragranular (L2/3) neurons in the mouse visual cortex. The reliability and specificity of multiphoton optogenetic stimulation were measured across multiple Cre lines and measurements of connectivity were verified by comparison to paired recordings and targeted patching of optically identified presynaptic cells. With a focus on translaminar pathways, excitatory and inhibitory synaptic connections from genetically defined presynaptic populations were characterized by their relative abundance, spatial profiles, strength, and short-term dynamics. Consistent with the canonical cortical microcircuit, layer 4 excitatory neurons and interneurons within L2/3 represented the most common sources of input to L2/3 pyramidal cells. More surprisingly, we also observed strong excitatory connections from layer 5 intratelencephalic neurons and potent translaminar inhibition from multiple interneuron subclasses. The hybrid approach revealed convergence to and divergence from excitatory and inhibitory neurons within and across cortical layers. Divergent excitatory connections often spanned hundreds of microns of horizontal space. In contrast, divergent inhibitory connections were more frequently measured from postsynaptic targets near each other.
Data availability
Source data files have been provided for all figures. Code to generate the primary figures within this manuscript is publically available at https://github.com/travis-open/twop_opto_data. This github repository includes a csv file containing quantitative electrophysiological features and metadata for all tested synaptic connections. Neurodata without borders (nwb) files containing original electrophysiological recordings are archived as a Dryad Digital Repository.
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two-photon optogenetics mapping in mouse visual cortexDryad Digital Repository, doi:10.5061/dryad.zs7h44jbc.
Article and author information
Author details
Christopher A Baker
Funding
Allen Institute for Brain Science (NA)
- Travis A Hage
- Alice Bosma-Moody
- Christopher A Baker
- Megan B Kratz
- Luke Campagnola
- Tim Jarsky
- Hongkui Zeng
- Gabe J Murphy
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols (#1807 and #2110) of the Allen Institute.
Copyright
© 2022, Hage et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Synaptic connectivity to L2/3 of primary visual cortex measured by two-photon optogenetic stimulation
eLife 11:e71103.
https://doi.org/10.7554/eLife.71103
