The Mouse Cortical Connectome, Characterized by an Ultra-Dense Cortical Graph, Maintains Specificity by Distinct Connectivity Profiles

Abstract

<p id="P1">The inter-areal wiring pattern of the mouse cerebral cortex was analyzed in relation to a refined parcellation of cortical areas. Twenty-seven retrograde tracer injections were made in 19 areas of a 47-area parcellation of the mouse neocortex. Flat mounts of the cortex and multiple histological markers enabled detailed counts of labeled neurons in individual areas. The observed lognormal distribution of connection weights to each cortical area spans 5 orders of magnitude and reveals a distinct connectivity profile for each area, analogous to that observed in macaque. The cortical network has a density of 97%, considerably higher than the 66% density reported in macaque. A weighted graph analysis reveals similar global efficiency but weaker spatial clustering to that reported in macaque. The consistency, precision of the connectivity profile, density and weighted graph analysis of the present data differ significantly from those obtained in earlier studies in the mouse. </p><p id="P2">Gămănuţ et al. investigation of anatomical cortico-cortical connections in mouse at the meso-scale level shows that almost all possible connections exist. Efficiency of the network and specificity of the connections is ensured by the existence of weighted connectivity profiles. </p>