Introduction: Various strategies are used to increase the sensitivity to activation in functional magnetic resonance (RMf) with bold contrast, including raised magnetic fields and group analysis. Although very important, study of the behaviour of the signal in a group (normal pattern) remains a problem in RMf.
Objectives: To study the behaviour of the signal in response to the motor paradigm using RMf with bold contrast at 3T in a group, by random effect analysis.
Results: The areas of most solid activation were the somatomotor area, the contralateral SMA and ipsilateral cerebellar area. Other areas showed greater variability (the number of persons who activated them and their localization). Analysis of the group showed close correlation between individuals both in the areas mentioned and in the basal ganglia, and to a lesser extent in ipsilateral premotor and somatomotor areas. There was wide variability in prefrontal, frontal, dorsolateral and parietal areas.
Conclusions: There is some variation in activation (number and position of the activated areas). SM, SMA and cerebellum have a high degree of inter individual anatomofunctional concordance. Activity in the basal ganglia, in spite of high inter individual anatomofunctional correlation, may not be easy to observe. Some areas are activated in certain persons but not on analysis of the group. This shows inter individual functional and/or anatomical variability. Such variation in activation should be remembered in subsequent analysis. Group analysis is useful for showing collective patterns which determine the most consistent areas on which to base subsequent individual analysis.