Edgar Douglas Adrian -Lord Adrian - İngiliz Fizyoloji Bilgini

ADRIAN, LORD (1889-1977)

Sir Charles Sherrington ile birlikte, sinirlerin beyinden organlara mesaj getirip götürme mekanizmasın, açıklayan İngiliz fizyoloji bilgini Bu mekanizma öğrenllene dek, sinir sistemindeki düzensizlikleri anlamak olası değildi 1932'de iki bilgin, Nobel Armağanı ile ödüllendirildi

Adrian's first research work was done with Keith Lucas, who was working on the impulses transmitted by motor nerves; he showed that, when a muscle fibre contracts, the passage of the nerve impulse that causes the contractions leaves the motor nerve in a state of diminished excitability Keith Lucas was, at the time of the First World War, thinking of improving the study of the electrical currents in nerves by amplifying them by means of valves, a method which Adrian was later to employ

First, however, Adrian went to London to take his medical degree and was, until the end of the First World War occupied with work on military patients suffering from nerve injuries or nervous disorders Returning to Cambridge in 1919 to take over Keith Lucas's laboratory, he began the work with which his name will always be associated In order to obtain a more sensitive detection of nerve impulses, he used the cathode ray tube, the capillary electrometer and amplification of the electrical impulses by means of thermionic valves, and was thus able to amplify them 5,000 times He succeeded in setting up a preparation consisting of a single end organ in a muscle of the frog, together with the single nerve fibre related to it and he found that, when the end organ is stimulated, the nerve fibre showed regular impulses with a variable frequency

With this apparatus he was able to record the electrical discharges in single nerve fibres which were produced by tension on the muscle, pressure on it, touch, the movement of a hair and pricking with a needle By 1928 he was able to publish his conclusion that a stimulus of constant intensity applied to the skin, immediately excites the end organ, but that this excitation progressively decreases for as long as the stimulation continues At the same time sensory impulses of constant intensity pass along the nerve from the end organ These sensory impulses are at first very frequent, but their frequency gradually decreases and as they decrease the sensation in the brain progressively diminishes As A V Hill (The Ethical Dilemma of Science, 1960) has said, Adrian, by thus showing that the afferent effect in a given neurone depends on the pattern in time of the impulses travelling in it, has provided a new quantitative basis of nervous behaviour

Later Adrian extended his investigations to a study of the electrical impulses caused by stimuli likely to cause pain, he concluded that, as Sir Henry Head had postulated as a result of his clinical studies, the nerve fibres which conduct impulses excited by pain probably do not pass further into the brain than the optic thalamus, but that all other sensory impulses can be distinguished in the sensory area of the cortex of the brain and he showed that the part of the cerebral cortex devoted to any particular kind of end organ is related to the special needs of the animal concerned Thus in man and the monkey the sensory area of the cerebral cortex devoted to the face and hand is relatively large, and relatively little is given to the trunk of the body In the pony the area devoted to the nostrils is as large as that devoted to the rest of the body; in the pig almost the whole of the sensory area of the cerebral cortex devoted to the sense of touch is given to fibres from the snout, which the pig uses to explore its environment

Subsequently, Adrian studied the sense of smell and the electrical activity of the brain and the variations and abnormalities of waves shown in the encephalogram, which Hans Berger, of Jena, had described in 1929 This work opened up new fields of investigation in the study of epilepsy and other lesions of the brain

For his work about the functions of neurones Adrian was awarded, jointly with Sir Charles Sherrington, the Nobel Prize for 1932

The results of Adrian's brilliant researches on the electrophysiology of the brain and nervous system were published in numerous scientific papers and in his three books, The Basis of Sensation (1927), The Mechanism of Nervous Action (1932) and The Physical Basis of Perception (1947) With others he wrote Factors Determining Human Behaviour (1937)