In cases in which it is necessary for the neurosurgeon to remove portions of the premotor area of the brain, he must first assure himself that in so doing he will not render the patient aphasic. In right-handed persons the center for motor speech always is located in the posterior part of the third left frontal convolution, just in front of the motor center for the face. In congenitally left-handed persons the speech functions usually are located in the corresponding area in the right cerebral hemisphere. The more pronounced the left handedness, the more certain it is that the speech function is located on the right side. Persons who acquire left handedness as a result of the occurrence of right hemiplegia early in life also usually will acquire complete right cerebral dominance, with the speech function located on the right side.
Occasionally, the neurosurgeon is confronted by the problem of
W. JAMES GARDNER. INJECTION OF PROCAINE INTO THE BRAIN TO LOCATE SPEECH AREA IN LEFT-HANDED PERSONS. Arch NeurPsych. 1941;46(6):1035–1038. doi:10.1001/archneurpsyc.1941.02280240090005