Structure of brain connectome and contactome in fly, mouse, and human

Analyzing networks of neurons is fundamental to understand the structure and function of the brain as a whole. However, it poses unique challenges, since even the simple questions of what the node positions are and what counts as an edge require careful consideration. Additionally, standard spatial network generative models are not applicable to neuronal networks since they can not take into account the interplay of the complex fractal neuron structure, spatial orientation, and biological wiring rules.

We analyze various aspects of complex neuronal networks in the fruit fly, mouse, and human brain [1-3] with the goal of gaining insight into their structure and building useful generative models. We focus on two distinct network types: synaptic networks (connectomes) that represents the possible pathways of nervous impulse transmission and physical proximity networks (contactomes) obtained from neuron meshes that represent important spatial constraints on synapse formation. By comparing the properties of connectomes and contactomes obtained from data and distance-based generative models, we highlight the prevailing motifs in connectomes that are relevant to the underlying biological wiring rules.

[1] Xu, C. Shan, et al. "A connectome of the adult drosophila central brain." BioRxiv (2020).

[2] Bae, J. Alexander, et al. "Functional connectomics spanning multiple areas of mouse visual cortex." BioRxiv (2021).

[3] Shapson-Coe, Alexander, et al. "A connectomic study of a petascale fragment of human cerebral cortex." BioRxiv (2021)