Background: It is a well known fact that language functions are primarily related to the left hemisphere in right handed individuals, there is still no agreement about hemispheric language dominance in left handers. The aim of this study is to evaluate the possibility of using functional Transcranial Doppler ultra sonography (TCD), as a non-invasive method for investigation of hemispheric language dominance and also to explore possible gender influence on hemispheric language representation.
Methods: We performed functional TCD during a word generation task, in 62 healthy volunteers (30 right handers and 32 left handers, 50% male and 50% female). All subjects were medical students in the age range of 22-29 years. Right or left handedness was determined using Edinburgh questionnaire. Two subjects were excluded from the study because of poor temporal windows. Mean blood flow velocity was measured in both right and left middle cerebral arteries (MCA) at rest and during a word generation task, and changes in flow velocities were compared.

Results: Increase of MCA blood flow velocity was observed in 55% (33 subjects) of the students in the left side, and in 45% (27 subjects) of them in the right side. Right hemispheric dominance was observed in 43.3% of right handers and 46.7% of left handers. Left hemispheric dominance was observed in 56.7% of right handers and 53.3% of left handers. Our results showed no significant right hemispheric language dominance in left handed subjects.
Conclusion: This study does not show significant difference in hemispheric language dominance between right and left handers, using functional TCD