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HARTLAYN (Hartline), H. Keffer

(. American biophysicist Nobel Prize in Physiology or Medicine, 1967)

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Biography HARTLAYN (Hartline), H. Keffer
December 22, 1903, Mr.. - March 17, 1983
American biophysicist Holden Hartlayn Keffer was born in Blumsburge (Pennsylvania), the son of Daniel and Harriet (Keffer) Hartlayn. His father, a professor of biology at public high school, instilled in him an interest in science. Visiting Lafayette College in Easton (Pennsylvania), he began to study visual perception in isopods, crustacean species living on land. Summer holidays he spent in the Marine Biology Laboratory at Woods Hole (Mass.), where he met with known neurophysiology. After receiving in 1923. the title of Bachelor of Science in Lafayette, X. entered medical school at Johns Hopkins. There he continued to study vision, to master the methods of study of electrical properties of the nervous system and in 1927. received a medical degree.
A year earlier, Edgar D. Adrian made the first recording of electrical impulses of individual nerve cells. In 1927, Mr.. Adrian recorded the electrical impulse to the optic nerve (which in reality is not independent, as represented by a beam of many hundreds of individual nerve fibers conger eel). In studying the work of Adrian H., as he later said, 'sought to expand this research: the use of a single analysis of receptors and neurons of the visual analyzer'. To acquire a solid foundation for further research in biophysics, X. within two years studying physics at school at Johns Hopkins, receiving a scholarship of the National Research Society. The scholarship is Eldridge Reeves Johnson, . designed to subsidize students, . trainee in foreign educational institutions, . allowed him to study for a semester at Leipzig University in Werner Heisenberg and another two semesters - the University of Munich.,
. Returning to the U.S. in the spring of 1931, X
. received a place in Dzhonsonovskom Institute of Medical Physics, University of Pennsylvania in Philadelphia, where he began to study the electrical impulses of individual visual elements. His research, as he said later, it helped 'a good choice of experimental animal' - a horseshoe crab. Visual Analyzer of the crab consists of the bundles of receptor cells located in the complex compound eyes, which are connected with the brain long optic nerve. The latter can be split into thin bundles, which are then easily split more than one remains active fiber. Thus X. and his colleagues to. H. Graham managed to register the first time in 1923. activity of single fibers of the optic nerve.
As in other studies conducted by Adrian sensory and motor nerves, X. also found in their experiments, . that information, . registered visual receptors, . sent as a package, . represents a set of homogeneous signal, . each of which reflects the intensity of light exposure on generating its visual receptor,
. The intensity of the reaction of the receptors depends on the degree of illumination. As he said later, H., 'the basic mechanism of the receptor is a registration character'.
In 1938. H. went on to study more complex visual analyzer vertebrate. Carefully and gently separating individual fibers of the optic nerves of frogs, he recorded the electrical activity of their. 'The results were unexpected, - he wrote. - Multiple fiber optic nerves react to light differently '. In contrast to the fibers of the optic nerve horseshoe crab, . reaction which was strictly identical, . Some fibers of the optic nerve of a frog only respond to dimming, . others - to increase its, . and others - the presence of light or its absence.,
. In Dzhonsonovskom Institute X
. acquainted with Ragnar Granit, developed a method for recording activity of individual cells of the retina. Particularly interested in the role of inhibition Granita. Research X. showed, . that some retinal ganglion cells, . has several layers of the visual receptors, and branching fibers in the optic nerve, . better respond to specific combinations of excitation and inhibition of receptor, . from which they receive signals,
. 'Obviously, - concluded H., - that the vast majority of complex processes going on in a thin layer of nervous tissue, which forms the retina. "
In 1940 ... 1941. H. worked as an associate professor of physiology at the Medical College of Cornell University in New York and then returned to Dzhonsonovsky Institute, where for the next 8 years, continued his studies. When the U.S. entered World War II, X. was assigned to do research of night vision in humans. In 1949, Mr.. he becomes the head of the department of biophysics at Johns Hopkins University.
Experiments X. showed that visual information before it reaches the brain, pre-processed in the retina, the results of his research suggested, however, several key approaches to understanding the mechanism. In the early 50-ies. he managed to improve the methods for recording electrical responses of individual visual receptors to the light. In these studies, he did not use the visual analyzer frogs and returned to the horseshoe-shaped crab, . because, . as he explained later, . 'relationship in his retina rather complex and therefore of interest, . but at the same time and are simple to learn. ",
. H
. found that the reaction of a single receptor cells to light largely depends on the degree of illumination of neighboring receptors. If these neighboring receptors brightly illuminated, the excitation of the studied receptor is inhibited. Therefore, the diffuse lighting usually causes weak responses, visual response, while the response to linear and angular coverage is stronger. All the observed X. relationships of neurons in the retina were inhibitory, his research confirmed that 'the formative influence of' inhibition, which, as shown by Charles C. Sherrington, is key in controlling the operation of the motor nerves, also plays a major role in the formation of visual responses. H. noticed that the network effect is the inhibition of the visual contrast enhancement, in which 'expressed by the intensity gradients in the image on the retina - edges and contours - amplified'. David X. David H. Hubel and Torsten Wiesel later showed that the visual information, which is held to the highest levels of the nervous system of vertebrates, including the brain, carries through the same processes to strengthen the image that X. found in the visual analyzer horseshoe crab. Most electrophysiological studies of the retina horseshoe crab has been implemented in conjunction with Floyd Retlifom at Rockefeller University, where X. was a professor since 1963, Mr.. to the resignation in 1974
X. shared the Nobel Prize in Physiology or Medicine 1967. with Granit and George Wald for the 'discovery of the basic physiological and chemical processes of the visual'. In presenting the award Carl Gustaf Bernhard of the Karolinska Institute said that the publication of X. 'gave us the basic idea of pulse coding in the visual receptors and the opportunity to get acquainted with the general principles of information in neuronal networks, which provide sensory function'. Bernhard noted that 'in respect of these principles are vital for understanding the mechanisms of brightness perception, shape and movement'.
In 1936, Mr.. H. married Elizabeth Kraus, a teacher of comparative psychology in the College of Bryn Mauer, they had three sons, who later became biologists. Portfolio X. always imprecise ideas. Amateur outdoor exercise, X. fond of mountain climbing and flying sport plane. In later years he liked to sail in the bay near his summer house in Maine, or together with Ragnar Granit in the Baltic Sea.
Died X. a heart attack March 17, 1983
Numerous awards and prizes X. included the Howard Crosby Warren Medal of the American Society of experimental psychologists (1948) and a prize of Alberta A. Michelson Institute of Technology (1964). He was awarded honorary degrees from Lafayette College, . University of Pennsylvania, . Rockefeller University, . University of Freiburg and Johns Hopkins University, he was a member of the National Academy of Sciences, . American Association for the Advancement of Science, . American Physiological Society, . American Philosophical Society and American Academy of Arts and Sciences.,

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HARTLAYN (Hartline), H. Keffer, photo, biography
HARTLAYN (Hartline), H. Keffer, photo, biography HARTLAYN (Hartline), H. Keffer . American biophysicist Nobel Prize in Physiology or Medicine, 1967, photo, biography
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