CEREBRAL DOMINANCE IN HEALTHY RIGHT AND LEFT HANDERS

Abstract

In 1861 the theory of lateralization and cerebral dominance was confirmed after the discovery of Paul Broca for specialization of left­ hemisphere to the function of speech. Before this theory it was thought that the two hemispheres are functionally equal. Functionallateralization was also supported by many other studies that recognized anatomical asymmetry between two hemispheres. The specialization of left hemisphere for speech function raised questions to be solved for example, if there are other lateralized functions rather than speech and if the cerebral dominance for language is always in left-hemisphere or may be in the right or both hemispheres of the brain. The aim of this study was to clarify the pattern of body sidedness, speech cerebral dominance, cognitive function, and brain electrical activity in the three handed groups (right-, left-, and mixed handers). The present study was carried on 50 healthy adult male medical students of Assiut University, Egypt. The age ofthe selected subjects ranged from 19 to 26 years old. All studied volunteers subjected to handedness, eyedness, footedness and earedness Stanly Coren inventories (1992) in attempt to I recogmze the dominant hand, foot, eye and ear for each subject. Repetitive Transcranial Stimulation (rTMS) was done for all studied volunteers in order to localize hemispheric dominance for language. • Also, cognitive function was investigated using auditory event related potential (ERP) in all studied groups. Brain electrical activity of three handed groups was recorded and analyzed using electroencephalogram (EEG).