FUNCTIONAL MR-IMAGING OF SEMANTIC INFORMATION-PROCESSING AND LEARNING-RELATED EFFECTS USING PSYCHOMETRICALLY CONTROLLED STIMULATION PARADIGMS

Functional magnetic resonance imaging (fMRI), in conjunction with care fully designed, psychometrically optimized stimulation procedures, was used to investigate the relation between brain activation and the pro cessing of word associations. A semantic discrimination task of word-p air similarity was performed by normal subjects (n=17) within a clinic al 1.5-Tesla whole-body MRI system. A color similarity task of psychom etrically equivalent difficulty, as indicated by behavioral data acqui red online during flc?RI, served as active control condition. Comparis ons between tasks dramatically improved results compared to comparison s between task and resting condition. The language paradigm selectivel y activated left frontal and left fronto-temporal areas. Cortical acti vation during the semantic task decreased significantly over three run s of the same word list and was paralleled by decreased reaction times . No such changes were observed in the active control condition indica ting selective learning of the language task only. When combined with psychological activation schemes and the acquisition of behavioral dat a, fMRI represents a powerful tool for the study of brain-behavior int eraction.