Mirror neurons have been a hot topic in neuroscience for the past decade or so, and more evidence has been amassed in recent years of their exciting properties. Mirror neurons are so interesting precisely because they fire or are activated both when an individual performs an action AND when that same individual merely observes another performing an action. This intriguing property has lead researchers to speculate that these neurons could be responsible for empathy and the learning of actions and language from others. Recent studies have been performed in an attempt to shed light on the properties and functioning of these neurons.
Before getting into a few of the recent studies, a short background of mirror neurons is needed. They were originally discovered by neurophysiologists at the University of Parma in Italy. While recording from a single neuron in a monkey's brain to observe how it would fire in response to the monkey's hand movements when grabbing and picking up food, they noticed that the neuron would also fire when watching a human caretaker pick up food! Thus, as is often the case in science, something was discovered when investigating something else.
But what is the namesake of Waves of Mu, Amy Caron's performance art piece currently running at Duke?
Well, many researchers have investigated the role of mirror neurons in human brains using an electroencephalogram (EEG). If you were to become a subject in one of these experiments, you might be wearing a cap that looks something like this:
This contraption allows researchers to measure the electrical activity of your brain waves through your scalp. If you were taking part in a study related to mirror neurons, the researchers might be looking for brain activity called mu waves that represent groups of neurons that fire in the frequency range of 8 - 11 Hz. The reason why mu waves are thought to correlate with mirror neurons is because these patterns of electrical activity in the brain lessen in intensity when the subject moves, has an intent to move, or observes the movement of another subject. This is similar to the patterns of activation in mirror neurons, so in studies mu wave activity is taken to be a marker of mirror neuron activity.
A few of the interesting studies that explore the function and use of mirror neurons involve their use in movement, imitation, learning, and perception. One study found that mu wave brain activity was normally suppressed by healthy individuals when moving their hand and when watching a video of a hand moving. However individuals with autism spectrum disorder showed mu wave suppression when moving their own hand, but NOT when watching a video of a hand moving. This study builds some evidence that autism might be related to a malfunctioning mirror neuron system.
Another cool study that relates to this blog involved mirror neurons and music. The cool thing about mirror neurons is that in addition to being active when seeing another perform a movement, they are also active when merely hearing a noise associated with a movement. Subjects in the study (who identified as non-musicians) were trained to play a short piece of music made up of 5 notes on a keyboard. After learning the music, they listened to the piece of music they had learned to play, a different song using the same 5 notes, and a completely different song using more notes than just the 5 original ones. Even though the subjects listened to the music without moving, the results of the study found that brain activity related to movement occurred when the subjects listened to the song that they had learned to play. The regions of the brain activated in the study are related both to movement and the observation of movement, and are also thought to be related to the mirror neuron system. This study adds to the evidence of mirror neurons as a way to learn movements.
SwM closing statement:
Mirror neurons: they help you learn to rock out!
Oberman LM, Hubbard EM, McCleery JP, Altschuler EL, Ramachandran VS, & Pineda JA (2005). EEG evidence for mirror neuron dysfunction in autism spectrum disorders. Brain research. Cognitive brain research, 24 (2), 190-8 PMID: 15993757
Lahav A, Saltzman E, & Schlaug G (2007). Action representation of sound: audiomotor recognition network while listening to newly acquired actions. The Journal of neuroscience : the official journal of the Society for Neuroscience, 27 (2), 308-14 PMID: 17215391