Journal Article

Dense connectomic reconstruction in layer 4 of the somatosensory cortex

Hennig, Philipp, Boergens, Kevin M., Loomba, Sahil, Berning, Manuel, Helmstaedter, Moritz, Staffler, Benedikt, Motta, Alessandro, Wissler, Heiko, Beining, Marcel

2019

Overview

The mammalian cerebral cortex is an enormously complex network of neuronal processes that are long and thin, branching, and extremely densely packed. This high packing density has made the reconstruction of cortical neuronal networks challenging. Motta et al. used advanced automated imaging and analysis tools to reconstruct with high spatial resolution the morphological features of 89 neurons and their connections in the mouse barrel cortex. The reconstruction covered an area more than two orders of magnitude larger than earlier neuroanatomical mapping attempts. This approach revealed information about the connectivity of inhibitory and excitatory synapses of corticocortical as well as excitatory thalamocortical connections. Science , this issue p. eaay3134 An advanced, automated imaging and analysis tool reconstructs high-resolution morphological features of 89 neurons and their connections. The dense circuit structure of mammalian cerebral cortex is still unknown. With developments in three-dimensional electron microscopy, the imaging of sizable volumes of neuropil has become possible, but dense reconstruction of connectomes is the limiting step. We reconstructed a volume of ~500,000 cubic micrometers from layer 4 of mouse barrel cortex, ~300 times larger than previous dense reconstructions from the mammalian cerebral cortex. The connectomic data allowed the extraction of inhibitory and excitatory neuron subtypes that were not predictable from geometric information. We quantified connectomic imprints consistent with Hebbian synaptic weight adaptation, which yielded upper bounds for the fraction of the circuit consistent with saturated long-term potentiation. These data establish an approach for the locally dense connectomic phenotyping of neuronal circuitry in the mammalian cortex.

• Publisher: American Association for the Advancement of Science,The American Association for the Advancement of Science
• Subject: Adaptation / Animals / Artificial intelligence / Automation / Axons / Axons - ultrastructure / Brain / Brain architecture / Cerebral cortex / Circuits / Connectome / Constraining / Cortex (barrel) / Data analysis / Dendrites / Developmental stages / Efficiency / Electron microscopy / Image analysis / Image processing / Image reconstruction / Image segmentation / Imaging, Three-Dimensional / Long-term potentiation / Male / Mammals / Mapping / Medical imaging / Mice / Mice, Inbred C57BL / Micrometers / Microscopy / Microscopy, Electron / Nervous tissues / Neural networks / Neuroimaging / Neurons - ultrastructure / Neuropil - ultrastructure / Organic chemistry / Packing density / Phenotyping / RESEARCH ARTICLE SUMMARY / Segmentation / Sensory Experience / Somatosensory cortex / Somatosensory Cortex - ultrastructure / Spatial discrimination / Spatial resolution / Synapses / Synapses - ultrastructure / Synaptic density / Synaptic strength / Thalamus / Upper bounds / Weight / Wiring