THE ROLE OF THE RIGHT-HEMISPHERE IN THE INTERPRETATION OF FIGURATIVE ASPECTS OF LANGUAGE - A POSITRON EMISSION TOMOGRAPHY ACTIVATION STUDY

We investigated cerebral activity in six normal volunteers using PET t o explore the hypothesis that the right hemisphere has a specific role in the interpretation of figurative aspects of language such as metap hors. WE also mapped the anatomical structures involved in sentence co mprehension. During regional cerebral blood flow measurement subjects were asked to perform three different linguistic tasks: (i) metaphoric al comprehension; (ii) literal comprehension of sentences; and (iii) a lexical-decision task. We found that comprehension of sentences compa red with the lexical-decision task induced extensive activation in sev eral regions of The left hemisphere, including the prefrontal and basa l frontal cortex, the middle and inferior temporal gyri and temporal p ole, the parietal cortex and the precuneus. Comprehension of metaphors was associated with similar activations in the left hemisphere, but i n addition, a number of sites were activated in the right hemisphere: the prefrontal cortex, the middle temporal gyrus, the precuneus and th e posterior cingulate. We conclude that the interpretation of language involves widespread distributed systems bilaterally with the right he misphere having a special role in the appreciation of metaphors.