How are brain waves measured?
Papez circuit
Theta waves are used to measure activity in mainly the hippocampus but can be used to measure other brain regions as well. Strong synchronization of theta waves in the hippocampus and anterior ventral thalamus has been observed. Although theta waves between the hippocampus and the anterior dorsal and anterior medial regions in the thalamus showed no synchronization, scientists have seen a marked increase in firing rates of the neurons in the brain regions. Overall, based on theta wave experimentation, some components of the Papez circuit have shown to indeed have a connection and work together. Also, theta waves are thought to be linked to learning and memory. Consequently, many scientists believe that the Papez circuit is involved with memory because of theta wave experiments. Some scientists have narrowed it down to specifically spatial and episodic memory.
Mu wave
Mu waves, also known as mu rhythms, comb or wicket rhythms, arciform rhythms, or sensorimotor rhythms, are synchronized patterns of electrical activity involving large numbers of neurons, probably of the pyramidal type, in the part of the brain that controls voluntary movement. These patterns as measured by electroencephalography (EEG), magnetoencephalography (MEG), or electrocorticography (ECoG), repeat at a frequency of 7.5–12.5 (and primarily 9–11) Hz, and are most prominent when the body is physically at rest. Unlike the alpha wave, which occurs at a similar frequency over the resting visual cortex at the back of the scalp, the mu wave is found over the motor cortex, in a band approximately from ear to ear. A person suppresses mu wave patterns when he or she performs a motor action or, with practice, when he or she visualizes performing a motor action. This suppression is called desynchronization of the wave because EEG wave forms are caused by large numbers of neurons firing in synchrony. The mu wave is even suppressed when one observes another person performing a motor action or an abstract motion with biological characteristics. Researchers such as V. S. Ramachandran and colleagues have suggested that this is a sign that the mirror neuron system is involved in mu wave suppression, although others disagree.