A Thousand Brains: A New Theory of Intelligence

by Jeff Hawkins

Each bump along the dendrite is one synapse. I’ve also highlighted an area around the cell body; the synapses in this area are called proximal synapses. If the proximal synapses receive enough input, then the neuron will spike. The spike starts at the cell body and travels to other neurons via the axon. The axon was not visible in this picture, so I added a down-facing arrow to show where it would be. If you just consider the proximal synapses and the cell body, then this is the classic view of a neuron. If you have ever read about neurons or studied artificial neural networks, you will recognize this description. Oddly, less than 10 percent of the cell’s synapses are in the proximal area. The other 90 percent are too far away to cause a spike. If an input arrives at one of these distal synapses, like the ones shown in the box, it has almost no effect on the cell body. All that researchers could say was that the distal synapses performed some sort of modulatory role. For many years, no one knew what 90 percent of the synapses in the neocortex did. Starting around 1990, this picture changed. Scientists discovered new types of spikes that travel along the dendrites. Before, we knew of only one type of spike: it started at the cell body and traveled along the axon to reach other cells. Now, we’d learned that there were other spikes that traveled along the dendrites. One type of dendrite spike begins when a group of twenty or so synapses situated next to each other on a dendri...