Mirror neurons, These are neurons with a curious property: they fire both when you do something, but also when you observe the same action in others. Much speculation surrounds the functional role of mirror neurons, and in particular how they might factor into developing empathy, and whether defects in the mirror neuron system could contribute to autistic spectrum disorders, which are characterized by poor cognitive empathy.
In this instance, we’re seeing a primitive kind of “motor empathy,” which might underlie cognitive empathy, our ability to understand others’ thoughts, feelings, motivations and so on from their outward behavior. Brodmann’s area 9, a part of the mirror neuron system in the brain, lit up when test subjects engaged in contagious yawning. This area of the brain has also been implicated in mentalizing, i.e., precisely in understanding other people’s mental states. Interestingly, in people with Major Depressive Disorder, we have found neurons in this area to be smaller, and glia—the support cells which are more numerous than neurons, and increasingly are understood to play more than just a passive role in thought—to be fewer and further between.
It remains to be seen exactly what role mirror neurons play in human empathy, but they’re certainly interesting. It’s fascinating that not only we can automatically do something because we saw someone else do it; this automatic act is caused by parts of our perfectly healthy brain not being able to distinguish between ourselves and our fellow human beings.