The EEG was turned into a musical instrument
Denis Strigun, Naked Science
American scientists have developed an encephalophone system for performing music using the electrical activity of the brain. Article by Deuel et al. The Encephalophone: A Novel Musical Biofeedback Device using Conscious Control of Electroencephalogram (EEG) is published in the journal Frontiers in Human Neuroscience.
Electroencephalography (EEG) is usually used to assess the functional state of subcortical and cortical structures of the brain, for example, in epilepsy. Compared to more modern tomography techniques, it has increased sensitivity, allowing you to track changes in millisecond time resolution. However, in addition to the main purpose, soon after the discovery (at the beginning of the XX century), scientists sought to apply the method to other areas, in particular, to turn electrical activity into visual images and sound. Thus, the occipital dominant (alpha) rhythm (PDR) was used for the design of performances in real time and the management of the party of percussion instruments.
Despite the development of neural interfaces and the successful application of EEG, including manipulation of the cursor of a computer mouse, it was not possible to adapt it to the performance of music in a stationary state. In a new paper, experts from the Swedish Institute of Neuroscience and other institutions described such a system. Like the prototypes of previous years, it is based on biofeedback technology. A cap with electrodes is put on a person's head, which is connected to a 19-channel encephalograph with an amplifier. The device sends signals via USB to the first computer, depending on the frequency and amplitude, encoding them into values from one to eight. Then, on the second machine, the latter are converted into notes.
How the system works (from an article in Frontiers in Human Neuroscience)
The authors involved 15 healthy people in the trials. Alpha- (accompanies relaxed wakefulness) acted as a source of brain activity and mu-rhythms (characteristic of complete physical rest). After converting the signals, the participants heard the sound of a piano of a certain pitch and learned to control the melody through intuitive modulation of the state. The tests themselves were preceded by a five-minute calibration period of the system. At this time, the volunteers had to close and open their eyes, changing (strengthening or weakening, respectively) thus PDR. This made it possible to determine the individual range of its oscillations. The sound was synthesized with a delay of 20 milliseconds.
Then the subjects were asked to reproduce through brain activity the notes to and re of the fourth and fifth octaves. Since the latter separated the maximum and minimum intervals, this made it easier to identify subjective differences. When the target sound was generated three times, the program synthesized the corresponding major chord and showed a new stimulus, in case of failure – a tritone, unpleasant to the ear. According to the tests, the average accuracy of performance in the group that used alpha rhythm was 67.1 percent. It took them about 38 attempts to master the technology. In the group with mu-rhythm, the indicators reached 57.1 percent and about 35 repetitions.
According to the authors, after the improvement, the new system can be used in art and science, including the development of neural interfaces. A distinctive feature of the method is the reliance on the mu-rhythm – potentially this allows it to be used in completely paralyzed patients.
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14.07.2017