From Big Medical Encyclopedia

DEXTRALITY — manifestation of functional asymmetry of hands, at a cut the leading role belongs to the right hand. Dextrality is determined by the bigger force of muscles of the right hand, perfection of coordination and praksisa (see), selectivities of operations. Dextral write and prefer to work the right hand.

Separate signs of P. note at children at the age of 8 — 9 months. By two years the right hand prevails already in all actions. In an origin and P.'s development social factors were of great importance. Work defined development of DEXTRALITY in the person to the most reasonable and perfect form. The item plays an important role in formation of the speech. At most of people compliance between the leading hand and the cerebral hemisphere dominating as the speech is noted.

At decrease in motive function of the right hand caused various patol. processes, activity and differentiation of the actions made by the left hand kompensatorno increases. It becomes possible owing to activation of symmetrically interfaced areas of the left and right cerebral hemispheres. In more exceptional cases when dominance of any hemisphere is absent, dominance of the right hand is changeable. In these cases DEXTRALITY forms in the childhood as a result of a training. At conscious actions, such as food, the letter, the person uses preferential right hand; in simpler operations or at actions in the heat of passion the left hand can prevail. P.'s identification matters for topical diagnosis of damages of a cerebral cortex and the correct organization of lechebnokorrektsionny actions at disturbances of the speech.

See also Left-handedness .

Bibliography: Bianki B. L. Evolution of pair function of brain hemispheres, JT., 1967, bibliogr.; Luriya A. R. Brain of the person and mental processes, M., 1970; M about with and d z e B. M. and Akbar-d and I am K. K. Functional symmetry and asymmetry of parencephalons, Tbilisi, 1973; Collins R. L. Origins of the sense of asymmetry, mendelian and non-mendelian models of inheritance, in book: Evolution and lateralisation of the brain, ed. by S. J. Dimond a. D. A. Blizard, p. 283, N. Y., 1977, bibliogr.; Levy J. Psycho-biological implications of bilateral asymmetry, in book: Hemisphere function of the human brain, ed. by S. J. Dimond a. J. G. Beamont, p. 121, L., 1974; Webster W. G. Hemispheric asymmetry in cats, in book: Lateralization in the nervous system, ed. by S. Harnad. p. 471, N. Y. a. o., 1977.

L. O. Badalyan.