Letters; August/September 2006; Scientific American Mind; by Staff Editor; 2 Page(s)

I am trying to comprehend the existence of mirror neurons in "A Revealing Reflection," by David Dobbs. More specifically, how can one differentiate between a normal neuron and a mirror neuron? What would the ratio be between the two? Would the ability to recall and replay memories be greater in those who have more mirror neurons versus those who have fewer?

DOBBS REPLIES: Mirror neurons are all premotor neurons--that is, specialized neurons in the cortex that fire to activate motor neurons, which in turn send signals to muscles to contract, relax or whatnot. Although the term "mirror neurons" seems to have taken, I think it more helpful to speak of "neuron mirroring," because what has been discovered is not a new type of neuron but a new activity and function in premotor neurons, which have already been heavily studied.