So it seems as though the “connectome” is the latest big thing in neuroscience. This is the brain’s wiring diagram, in terms of the connections between neurons and on a larger scale, between brain regions.
We certainly won’t understand the brain without getting to grips with the connections but equally, it’s not the whole story. I previously emphasised that the brain is not made of soup; it’s not made of spaghetti, either.
Connectomics does however unquestionably provide some of the prettiest images in neuroscience. And they just got prettier, with a new technique for visualizing connections, just revealed in Neuroimage: Circular representation of human cortical networks for subject and population-level connectomic visualization.
See above. It’s a rather lovely vista (for which the authors Irimia et al share credit with the folks behind the Circos visualization tool they used).
All you need are some MRI scans, and a lot of image processing, and you can produce one of these “Connectograms”. But what does it mean? Here’s the authors’ description:
The outermost ring shows the various brain regions arranged by lobe (fr — frontal; ins — insula; lim — limbic; tem — temporal; par — parietal; occ — occipital; nc — non-cortical; bs — brain stem; CeB — cerebellum) and further ordered anterior-to-posterior. The color map of each region is lobe-speci?c and maps to the color of each regional parcellation.
In other words, the outer ring is just a list of brain regions, each with an assigned colour. The inner rings tell us about those regions:
Proceeding inward towards the center of the circle, these measures are: total GM volume, total area of the surface associated with the GM–WM interface (at the base of the cortical ribbon), mean cortical thickness, mean curvature and connectivity per unit volume. For non-cortical regions, only average regional volume is shown.
So each of the five inner rings displays data about one aspect of brain anatomy, for each of the regions. The colors are a heat map of the numbers.
Finally, the lines between regions represent the degrees of connectivity between regions via white matter tracts, as measured with diffusion tensor imaging:
The links represent the computed degrees of connectivity between segmented brain regions. Links shaded in blue represent DTI tractography pathways in the lower third of the distribution of FA, green lines the middle third, and red lines the top third (see text for details).
You can also make a pooled connectogram of the average neuroanatomy across a group of people. Still, it remains to be seen whether these are as useful as they are beautiful.
Irimia A, Chambers MC, Torgerson CM, and Van Horn JD (2012). Circular representation of human cortical networks for subject and population-level connectomic visualization. NeuroImage PMID: 22305988