Counting action potentials

A very interesting (non-firewalled) paper by Chamberland et al in PNAS reveals a new kind of transfer logic for brain cells. The neural circuit is the first synapse in the so-called hippocampal tri-synaptic loop, an area of the brain that I’ve been very interested in from the standpoint of my own research. The usual suspects for informational transfer between neurons at the synapse are either frequency or timing encoding of action potentials. Here the author’s demonstrate a new type of encoding such that the post-synaptic neuron, a CA3 pyramidal cell actually counts the incoming number of action potentials to determine (decide) if it in turn, will fire an action potential.

Why is this important? How information is gated in brain circuits is crucial to how they compute on information (just as it is for non-biological digital computers). If we want to understand (from a reverse-engineering standpoint) how human brains do the cool things they do, then we have to be on the look out for phenomena like the one described here, because therein lies a clue to brain computation.

I’ll just add, that this neural circuit, the hippocampus, turns out to be crucial to learning and memory–particularly the kind called episodic, or what I describe to my students as “the movie of your life”.