Electroencephalogram (EEG)

This article needs to be cleaned up to conform to a higher standard of quality. Please help SensorWiki by editing this page.

Summary

An electroencephalogram or EEG is a result of the neurophysiologic measurement of the electrical activity of the brain by recording from electrodes placed on the scalp, or in the special cases on the cortex. It represents so-called “brainwaves”. It is used to assess brain damage, epilepsy and other problems. In some jurisdictions it is used to assess brain death. EEG can also be used in conjunction with other types of brain imaging.

Measuring

There are four distinct classifications of EEG signals. Delta waves tend to have a frequency of 3 Hz and lower. They have the highest amplitude and are typically most prevalent during sleep cycles. Theta waves have frequencies between 3.5 to 7.5 Hz and are typically most prevalent when drowsy or attempting to repress an action. Alpha waves have frequencies between 7.5 and 13 Hz and are most prevalent during meditative, relaxed states. Finally, beta waves have frequencies of 14 Hz or higher and are prevalent when a person is awake and alert.

Classifications of EEG waves and their typical graphs

EEGs can typically be measured with any number of electrodes placed around the head. In medical diagnoses, the 10-20 system of electrodes is used to ensure reproducibility. The 10-20 system refers to placing electrodes at distances of 10% or 20% of the distance of the front-back or right-left distance of the skull.

Electrode placement in 10-20 system for EEG

Uses in musical applications

The MIDI controller BioMuse, as outlined in the original paper by Lusted and Knapp used EEG in conjunction with EOG and EMG to control MIDI output. The current version of the BioMuse typically showcased by Atau Tanaka no longer uses EEG.

“Music for Solo Performer” is a piece by the composer Alvin Lucier which measures the alpha waves of a human performer, and then uses the electrical signals measured and uses it to control percussive instruments around the performer. The percussion is controlled by amplifying the alpha waves, and playing the amplified waves through loudspeakers on or near the percussion. The sound out of the loudspeakers then vibrates the percussive membrane of the instrument and creates the sound for the piece.

The BCMI Piano by Eduardo Miranda et Al. at Plymouth University ICCMR is a piano that is controlled using signals measured from a performer’s EEG. The EEG is connected to a MIDI-enabled acoustic piano. A MIDI-enabled acoustic piano is a typical acoustic piano that can be controlled using MIDI signals. The EEG signal from the performer is measured and then passed through an algorithm. The algorithm generates the music using rules that it has been trained in and outputs MIDI signals to the piano. The EEG of the performer influences this algorithm, which thus changes the MIDI signals being sent to the piano.

The DECONcert was a series of art exhibits and concerts held by researchers at the University of Toronto that used EEG signals from various performers to create sound. One concert had “participants simultaneously and collectively adjusted the musical environment with their brainwaves while remotely connected to groups in other countries”.

References

sensors/electroencephalogram.txt · Last modified: 2016/04/11 20:14 by patrickignoto
Recent changes RSS feed Creative Commons License Donate Minima Template by Wikidesign Driven by DokuWiki