FUNCTIONAL MAGNETIC-RESONANCE-IMAGING OF HUMAN BRAIN ACTIVITY IN A VERBAL FLUENCY TASK

Objectives-Functional MRI (fMRI) holds the promise of non-invasive map ping of human brain function in both health and disease. Yet its sensi tivity and reliability for mapping higher cognitive function are still being determined, Using verbal fluency as a task, the objective was t o ascertain the consistency of fMRI on a conventional scanner for dete rmining the anatomic substrate of language between subjects and betwee n sexes. Comparison was made with previous PET studies. Methods-Using a 1.5 Tesla magnet and an echoplanar pulse sequence, whole brain fMRI was obtained from 12 normal right handed subjects (6 males and 6 femal es) as they performed a verbal fluency task. Results-A broadly consist ent pattern of response was seen across subjects. Areas showing activa tion changes included the left prefrontal cortex and right cerebellum, in agreement with previous PET O-15-H2O studies, In addition, signifi cantly decreased responses were seen in the posterior cingulate and ov er an extensive area of mesial and dorsolateral parietal and superior temporal cortices. The male cohort showed a slight asymmetry of pariet al deactivation, with more involvement on the right, whereas the femal e cohort showed a small region of activation in the right orbitofronta l cortex. There were individual task related regional changes in all 1 2 subjects with the area showing the most significant change being the left prefrontal cortex in all cases. Conclusions-Magnetic resonance s canners of conventional field strength can provide functional brain ma pping data with a sensitivity at least that of PET. Activation was see n in left prefrontal and right cerebellar regions, as with PET. Howeve r, decremental responses were seen over a much larger area of the post erior cortex than had been anticipated by prior studies. The ability t o see a response in each subject individually suggests that fMRI may b e useful in the preinterventional mapping of pathological states, and offers a non-invasive alternative to the Wada test for assessment of h emispheric dominance. There were no gross differences int the pattern of activation between male and female subjects.