1 — Brain Computation Is Organized via Power-of-Two-Based Permutation Logic

In the search for a “functional connectivity motif” (FCM) — a universal computation network that tiles across cortex — this paper explores the self-dubbed Theory of Connectivity, a hypothesis that states that a single excitatory motif consists of $2^{i} - 1$ (where $i$ is the number of inputs) neurons, where there are “principal projection neuron cliques” whose outputs converge into all possible converged inputs for downstream neurons.

The authors test and seem to confirm this this by measuring from tetrode arrays inserted into different layers and regions of cortex, as well as by stimulating via optogenetics.

I may be misunderstanding the empirical findings — which is reasonable, considering the closest I ever came to a neuroscience wet-lab was a genomics wet-lab, which is arguably a pretty different thing — but I have a hard time reconciling the spatial resolution of the recording arrays with the confidence of the conclusions they make.

Even so, the concept of a $2^{i} - 1$ FCM is very enticing; I expect we’ll begin to see the anatomical underpinnings of these motifs — if they exist — in upcoming large-scale electron-microscopy studies.