[The relation of speech to the right and left cerebral hemispheres]

Verbal speech functions are localized in right-handed subjects nearly exclusively and in left-handed ones mostly in the left hemisphere. Much information on these functions has been obtained by studying patients affected with spontaneous damages, as well as after hemispherectomy, after severing the corpus callosum, and during electric stimulation of the brain in neurosurgical procedures. In the presylvian region of the hemisphere dominant for speech, a region for the production and identification of speech was found, surrounded by an area for shortterm verbal memory. The predominance of the right ear in recognizing verbal stimuli, established by the dichotic test, applies to the population rather than to the individual. The substance of verbal dominance of the left hemisphere lies in the prevalence of its capacity to distinguish rapid acoustic sequences and to produce them. Observations made on deaf-mute patients with sign language have demonstrated that humans possess a genetically determined ability to develop speech, regardless the modality. Speech functions of the right hemisphere concern mostly nonverbal prosodic components of speech.