Identification of Motor Functions Based on an EEG Analysis

Background

The history of the discovery of the EEG started with Richard Caton, a Liverpool physician and medical school professor, who discovered electrical brain signals by probing the surface of the exposed brains of animals. He published his first results in 1875. Two years later, Caton reported that when he interrupted light falling on an animal's eye, he detected negative variations in the electrical activity of the brain. He also discovered that electrical activity in the brain occurred on the opposite side from the eye. Adolph Beck of Poland repeated and published his work about 15 years after Caton, in 1890. However, he went beyond Caton when he found that though a sensory stimulus, such as a sound clap, induced a response at a single point, there was also a brain-wide interruption of the slow, even pattern of the brain waves. It was not until 1949 that the reticular activating system of the brain was discovered, which had an important role in controlling the states of the brain. Hans Berger, an Austrian psychiatrist was the first to record electroencephalographs from humans. In 1897, Berger became aware of Richard Caton's work. His experiments with animals were inconclusive by 1910, but after the First World War he decided to look for the EEG in the human brain. In the early years of the 1920s Berger obtained his first results in subjects who had skulls with gaps under the skin where a piece of bone was missing. He made recordings on moving photographic paper with a wavy spot of light. This was how Berger found the regular waves at about 10 cycles per second that he named the Alpha waves. Later Berger found that Alpha waves diminish during sleep, general anaesthesia, and cocaine stimulation. While Alzheimer's disease and multiple sclerosis altered EEG, he was rather disappointed that many illnesses including schizophrenia and aphasia showed only little or no obvious effect on the recorded EEG. He reported that the Alpha wave frequency was decreased in patients with high intra-cranial pressure resulting from injuries and found, significantly, that epileptic patients had large amplitude waves. Nowadays, EEG is a conventional technique for measuring the brain’s activity and for diagnosing various nervous complaints (Yamada & Meng, 2010).