Abstract
Although the recent brain activation studies utilizing positron emission tomography (PET) have provided important neurophysiological informations concerning the functional neuroanatomy of language processing, the results of those studies differed each other possibly due to the variability in the paradigm designs. This article reviews the results of selected PET activation studies using verb generation tasks based on the right-handed normal subjects in the past 10 years. In the verb generation tasks, subjects were asked to think of verbs as many as possible which are associated to the visually or auditorily given nouns. Resting state or word repetition was often used as control condition. The image subtraction of the control condition from the verb generation demonstrated consistent activation foci in the left middle frontal gyrus, inferior frontal gyrus including Broca's area, anterior cingulate gyrus, superior temporal gyrus including Wernicke's area, and supplementary motor area, whereas there were less consistent activation foci in the insula, parietal cortex, thalamus and basal gagnlia on the left hemisphere. Activation foci were also seen in the right frontal, temporal and occipital cortices although the degree of activation was less significant as compared to the left hemisphere. In the infratentorial structures, activation was observed in both cerebellar hemispheres with a predominancy of the right side, vermis and brain stem. From the results the previous studies, retrieval of verbs in response to the presentation of nouns reuuired activation in the extensive brain areas involving the left frontal and temporal lobes as well as cerebellar hemisphere. There was no significant difference in the activation patterns for verb generation in Japanese language as compared with English or other European languages. This may indicate that the verb generation processing shares fundamentally the common brain areas regardless of language.
