Must-Read: Ari Berkowitz: Is Your Nervous System a Democracy or a Dictatorship?

Must-Read: Neuronal dictatorship for speed of response, neuronal democracy for accuracy of perception and movement:

Ari Berkowitz: Is Your Nervous System a Democracy or a Dictatorship?:

For some behaviors, a single nerve cell does act as a dictator… touching a crayfish on its tail; a single spike in the lateral giant neuron elicits a fast tail-flip that vaults the animal upward, out of potential danger. These movements begin within about one hundredth of a second of the touch…. Each dictator neuron sits at the top of a hierarchy, integrating signals from many sensory neurons, and conveying its orders to a large set of subservient neurons that themselves cause muscle contractions. Such cellular dictatorships are common for escape movements, especially in invertebrates….

But these dictator cells aren’t the whole story. Crayfish can trigger a tail-flip another way too – via another small set of neurons that effectively act as an oligarchy…. This redundancy makes sense: it would be very risky to trust escape from a predator to a single neuron, with no backup–injury or malfunction of that neuron would then be life-threatening. So evolution has provided multiple ways to initiate escape. Neuronal oligarchies may also mediate our own high-level perceptions, such as when we recognize a human face.

For many other behaviors, however, nervous systems make decisions through something like Sherrington’s “million-fold democracy”… when a monkey reaches out its arm… a neuronal election in which some neurons vote more often than others…. Numerous other examples of neuronal democracies have been demonstrated. Democracies determine what we see, hear, feel and smell…