Interindividual variation of cerebral activation during encoding and retrieval of words

The aim of the present study was to compare the cerebral activation associa ted with encoding and retrieval in individual subjects with the average act ivation in the same group of subjects. Twelve volunteers performed two para digms: 1) intentional encoding of words, and 2) recognition of learned word s intermixed with new distracters. Echo-planar magnetic resonance imaging ( MRI) of BOLD signal changes was used to compare cerebral activation between active and resting conditions. During encoding, activation of the left pre central gyrus related to the motor response was observed in some subjects. Averaged data showed increased activation of the left precentral gyrus, the supplementary motor area (SMA), the left inferior frontal gyrus and in the left temporo-occipital junction. During recognition, motor response-relate d activity was found in the precentral cortex and SMA in most subjects. Act ivation in other brain areas showed considerable interindividual variation. In the entire group, recognition showed activation of the left dorsolatera l prefrontal cortex, the precentral gyrus, the SMA, and the temporo-occipit al junction. The total amount and the distribution of task-related cerebral activation varies considerably between individuals and might correspond to individual preferences of cognitive strategies. The investigation of these interindividual variations will be an exciting scientific challenge in the near future. (C) 2000 Editions scientifiques et medicales Elsevier SAS.