February 01, 2008

Connecting With the Macaque

While I'm still at posting my latest renderings and Flickr stuff, here is some a graph of the brain connectivity of the Macaque (click for a larger version):

Neuroanatomical Connectivity Macaque

This is based on the data in the brainmaps.org table of macaca mulatta connectivity. Each node is a brain area, with size denoting betweenness centrality and colour denoting graph distance from the visual cortex. yEd's grouping algorithm has been used to cluster groups of nodes.

The two big orange nodes are claustrum and the reticular nucleus of thalamus. Their cluster contains lots of visual cortex. The cluster below it contains somatosensory cortex, the one to the lower left seems to be motoric, the one above it seems to be secondary somatosensory. The one on top of that (left of the big cluster) seems to be cingulate cortex. This is nicely connected to the medial temporal system, which constitutes the three clusters to the upper left (the right centers on entorhinal cortex, the upper left is dentate gyrus and the lower left is cornu ammonis and subiculum feeding back). The small nodes on top are parasubiculum and presubiculum and area 31, limbic structures that in reality have many more connections.

Overall, I'm pretty impressed by how the clustering manages to get a rough outline of different systems. But the claustrum and reticular nodes seem to be hogging the network. So I tried removing them, and got this:

Neuroanatomical Connectivity Macaque

The result is just four big clusters. The right cluster is heavily visual, the lower cluster is somatosensory and motoric, the middle cluster limbic and the left cluster is the hippocampal system.

Running a second pass of clustering neatly divides the lower group into a motoric, primary somatosensory and a secondary somatosensory cluster. The limbic cluster divides into a MTL and a cingulate cluster, while the visual splits into a primary cluster, a temporal and a parietal cluster. Very cool.

Now the question is whether this is due to real differences in connectivity or that people have simply researched the connections that would make sense. How many have looked for a direct hippocampus-V1 connection?

Posted by Anders3 at February 1, 2008 01:52 PM