Brain Dynamics:

Spike Challenge 2

Opposite inputs can make the same spikes

Whatever this spiking mechanism is, it has some strange properties!

Letís take a neuron and try to make it spike. The usual way to do this is give it positive current inputs:

But now letís give it the opposite, negative input -- pushing the neuron's voltage down and away from the spike.

Incredibly, we still get a spike!

The third mathematical challenge, then, is that the spiking mechanism must be highly nonlinear Ė what comes out of the neuron is most certainly NOT predictable by just summing what goes in!

Brain visualizations courtesy of Chris Johnson and Nathan Galli, Scientific Computing and Imaging Institute, University of Utah