Experiments using brain stimulation, PET imaging and behavioral procedures were initiated to identify the neuroanatomic basis underlying different types of memo and language disorders exhibited by patients with neurologic disorders. Results from encoding and memory tasks showed that left temporal lobe is critical for phonological processing whereas semantic memory involves mesial as well as lateral temporal-parietal cortex. Brain stimulation, intracarotid amytal injection and PET imaging in a bilingual patient showed that the left hemisphere assumes a dominant role in primary and secondary languages. The brain representation of the primary language, however, is more focal in the left hemisphere. The second acquired language utilizes a larger cortical region in the left and dominant brain, and as well, the right hemisphere for paralinguistic functions.
