JournalNeural Excitability, Synapses, and Glia

FluoEM, virtual labeling of axons in 3-dimensional electron microscopy data for long-range connectomics

Rendering of a subvolume of the 3-channel confocal image stack showing axonal long-range projections from M1 cortex (green), S2 cortex (red) as well as stained blood vessels (blue).

The labeling and identification of long-range axonal inputs from multiple sources within densely reconstructed EM datasets from mammalian brains has been notoriously difficult because of the limited color label space of EM. Here, we report FluoEM for the identification of multi-color fluorescently labeled axons in dense EM data without the need for artificial fiducial marks or chemical label conversion. The approach is based on correlated tissue imaging and computational matching of neurite reconstructions, amounting to a virtual color labeling of axons in dense EM circuit data. We show that the identification of fluorescent light- microscopically (LM) imaged axons in 3D EM data from mouse cortex is faithfully possible as soon as the EM dataset is about 40-50 µm in extent, relying on the unique trajectories of axons in dense mammalian neuropil. The method is exemplified for the identification of long-distance axonal input into layer 1 of the mouse cerebral cortex.vioral relevance for most individuals, require the use of more individual aesthetic sensibilities that reflect varying experiences and different sources of information.

Drawitsch, F., Karimi, A., Boergens, K.M., Helmstaedter, M. (2018). eLife 7:e38976.