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The term Brain wave has multiple meanings. For our purposes, we will be using it as the layman's term to describe the fields detected via Electroencephalography (EEG). There are 6 main wave patterns listed from lowest to highest frequency with main characteristics [1] : 

Seizure EEG

EEG of a patient that experiences a seizure. The effect is obvious.

 *Delta waves (<4Hz). Seen during the slow sleep phase of sleep, as well as with certain brain abnormalities. Not useful for C-BCI purposes.

  • Theta waves (4-7Hz). Seen more rarely with increasing age, associated with meditative, tired and relaxed states.
  • Alpha waves (7-14Hz). Amplitude increases with relaxation and decreases with mental exertion. Commonly used in C-BCI devices.
  • Mu Waves (8-13Hz). Overlaps with Alpha waves, Mu waves exist when during meditation and other times when motor neurons are not in use. In this way, Mu waves provide a source of data for C-BCI devices that is unique to Alpha and Beta waves.
  • Beta waves (15-30Hz). Amplitude decreases with rapid thinking (and anxiety - imagine the 'flight or fight' response as an example). It is also related to physical activity, and is commonly used in C-BCI devices.
  • Gamma waves (30-100Hz). Still somewhat mysterious in their cause, Gamma waves are thought to relate to consciousness itself. [2] Not useful to C-BCI for anything but empirical training. (which carries significant dangers, particularly in this frequency).

The nature of brainwaves remains largely speculation, as they deal with the net summation of neural activity in an area and does not necessarily reflect the purpose of the activity of indivual neuron interactions.

ReferencesEdit

  1. Niedermeyer E. and da Silva F.L. (2004). Electroencephalography: Basic Principles, Clinical Applications, and Related Fields. Lippincot Williams & Wilkins. ISBN 0-7817-5126-8.
  2. Vanderwolf CH (Feb 2000). "Are neocortical gamma waves related to consciousness?". Brain Res 855 (2): 217–24. doi:10.1016/S0006-8993(99)02351-3