Regional cerebral blood flow during self-paced repetitive Iifting tasks with a precision grip

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Regional Blood flow (rCBF) was measured using a SPECT with 1-123 IMP tracer during resting, holding and self-paced repetitive lifiting of a small object with the precision grip. For the lifting task, two object weight conditions were tested ; one with a constant weight (400g) and the other with variable weights (200,400 and 600g). In all conditions, visual input was minimized using an eyemask. A SPM was used to test the rCBF increase and decrease statistically. There was no significant rCBF increase or decrease due to holding of the object, while during lifting a constant weight, there was a significant increase in the areas of contra lateral primary motor cortex and primary sensory cortex. A tendency of increase was also revealed for the contra lateral supplementary motor area. In addition, a significant rCBF decrease was observed in the contralateral areas related to vision (Brodman's area 8,37, and 17). The findings suggest that these are the primary and essential areas for the control of lifting tasks with the precision grip. When the variable weight condition was compared with the constant weight condition, a significant rCBF increase was found for the contralateral cingulate gyrus which corresponded to Brodman's areas 24/32. There was also significant increase in the contra lateral inferior prefronal cortex (area 11) and the ispliateral occipital region (Brodman's areas 2/40). The results thus suggest that these areas plays an important role in the control of quickly adjusting the grasp forces to the changes in weight of objects being lifted.