Hair whorl--a genetically bound phenomenon in testing of right-handedness and hemispheric dominance
Tichý, J.
Casopis Lekaru Ceskych 145(12): 955-958
2006
ISSN/ISBN: 0008-7335 PMID: 17323619 Document Number: 602404
The importance of normal development of hemispheric dominance and its significance for the development of an individual is sufficiently known. The internationally not well known procedure according to Zlab (1) represents one of the most suitable examinations for right-handedness and laterality testing. In our study we used one of the most popular questionnaires for phenotype testing of handedness- Edinburgh's Inventory (2). According to this questionnaire we have examined 65 children 10 years of age (+/- one year), and classified them into 3 groups: a) pure right-handed (n = 51), b) pure left-handed (n = 5) (all have fulfilled +90-100% resp. -90-100% of answers on corresponding ten questions) and c) a group of mixed laterality--ambidextrous (n = 9). The questionnaire we have accomplished by means of objective testing of hair whorl direction presupposed clockwise in right-handed and counter clockwise in lefthanded. Some of other tests we used turn to be more reliable than lid opening and using a broom (upper hand) by "dominant" hand used in Edinburg's Handedness Inventory. We have examined also hand, elbow, knee and leg joints excursibiliy (enlarged passivity and/or diminished muscle tonus) to define cerebellar dominance: right cerebellar hemisphere in right-handed and left cerebellar hemisphere in left-handed. In the group of pure right-handers we found clockwise hair whorl in 23 of 25 boys. In girls (probably due tu various hair combing) we found clockwise hair whorl only in 12 of 26 children. Examination of the hair whorl direction seems to be enrichment for a quick clinical phenotype and genotype laterality testing.