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Allen Institute

Feb 8 • 8 tweets • 5 min read

Brain mapping requires thorough synaptic measurements with diverse subclasses of neurons. Check out our latest #neuroscience publication: “Synaptic connectivity to L2/3 of primary visual cortex measured by two-photon #optogenetic stimulation”
📄 elifesciences.org/articles/71103 🧵 1

@trav_ha

Our team [including @trav_ha, @timjarsky, @HongkuiZeng & @lukecampagnola] + @bakermind combined optogenetic stimulation with simultaneous multicellular recording to measure synaptic connections within cortical microcircuits. #optogenetics🧵 2

The reliability of multiphoton optogenetic stimulation was measured across Cre lines & connectivity measurements were verified by #patchclamp recordings 🧵 3

Connections to L2/3 pyramidal neurons were deeply characterized (>10,000 possible connections tested). Consistent with the canonical cortical microcircuit, excitatory connections were most frequently observed from layer 4 while inhibitory connections were abundant within L2/3 🧵4

Interestingly, experiments also revealed strong excitatory connections from layer 5 intratelencephalic neurons and potent translaminar inhibition from multiple interneuron subclasses. 🧵 5

Additional features of synaptic connections including strength, dynamics, patterns of convergence and divergence were measured and compared across presynaptic and postsynaptic cell subclasses. 🧵 6

The combination of photostimulation and multicellular recording revealed converging inputs to, and diverging outputs from, single cells across hundreds of microns. Outputs from a single cell onto connected partners could differ in strength by a factor of 10 or more. 🧵 7

Data and analyses have been shared at github.com/travis-open/tw… and doi.org/10.5061/dryad.… #openscience🧵 8

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More from @AllenInstitute

Allen Institute

@AllenInstitute

Jan 24

Different cell types in the brain have their own connectivity rules and patterns. In a recently published study, our #neuroscience researchers took a deep dive into the connectomics of an important but enigmatic cell type, the chandelier cell. 🧵1

📄 elifesciences.org/articles/73783

🔬 💻 Using large-scale #electronmicroscopy with automated segmentation, we mapped the complete axo-axonic input onto pyramidal neurons (1,929 synapses in total, 1,127 from chandelier cells) in a volume of layer 2/3 of mouse visual cortex. #ImagingTheFuture #BrainMapping🧵2

By completely reconstructing the presynaptic chandelier cells, we found a novel principle of connectivity, where a group of interneurons are essentially interchangeable, but their postsynaptic targets individually regulate the amount of input they receive from the population. 🧵3

Read 7 tweets

Allen Institute

@AllenInstitute

Oct 31, 2019

@nature

In a new study out in @nature, our researchers make a big step forward in our quest to map the brain. Study findings lay the groundwork to better understand brain disorders & diseases such as #Alzheimers and #schizophrenia.

alleninstitute.org/what-we-do/bra…

This new study describes a high-resolution expansion of our #openscience Allen Mouse Brain Connectivity Atlas-- the most detailed map of connections in a mammalian brain to date. Access via: connectivity.brain-map.org

Using a computational approach, our researchers found that different sections of the cortex and thalamus can be mapped into a hierarchy, much like a company’s org chart – although not all connections followed this hierarchical structure. #brainmapping