Mu wave

Mu waves, also known as the comb or wicket rhythm, are electromagnetic oscillations in the frequency range of 8-13 Hz and appear in bursts of at 9 - 11 Hz. Mu wave patterns arise from synchronous and coherent (in phase/constructive) electrical activity of large groups of neurons in the human brain. This wave activity appears to be associated with the motor cortex (central scalp), and is diminished with movement or an intent to move, or when others are observed performing actions. EEG oscillations in the mu wave range over sensorimotor cortex are thought to reflect mirror neuron activity. Mu waves are commonly detected by electroencephalography (EEG) or magnetoencephalography (MEG). The mu wave is an alpha wave like variant.

History
Mu waves have been studied since the 1930s, and are referred to as the wicket rhythm because the rounded EEG waves resemble croquet wickets. In the 1950s, Gian Emilio Chatrian showed that the amplitude of mu waves could be suppressed by physical movements. Later studies showed that the simple intent to move, or certain other visual or mental tasks also can suppress mu wave amplitude.

Neurofeedback
EEG neurofeedback Training (often called neurotherapy or neurofeedback) is a method that enables persons to alter their brain waves via feedback regarding their present state. Research has suggested that a dysfunctional mirror neuron system may explain the pathology observed in autism spectrum disorders (ASD). Mirror neurons and mu waves may play a critical role in the ability to understand and imitate others' behaviors. Early research results, on enhancing mu wave activity through biofeedback a therapy for autism, have been promising thus far.

Scientists are training subjects to learn how to control the amplitude of mu waves by visualizing motor activities, such as smiling, chewing, or swallowing, and have developed a system that sends mu wave output code to drive a cursor up or down on a computer screen. Users can be trained to move a cursor with mental effort alone. The researchers hope that this system will someday provide a means of communicating for profoundly disabled individuals.

Reference
Oberman LM, Hubbard EM, McCleery JP, Altschuler EL, Ramachandran VS, Pineda JA. "EEG evidence for mirror neuron dysfunction in autism spectrum disorders". Brain Res Cogn Brain Res. 2005 Jul;24(2):190-8