Motor representation of the hand in the human cortex: an f-MRI study with a conventional 1.5 T clinical unit

The purpose of this study was to show a gradient of possible bilateral acti vation for movements of the non-dominant vs, dominant hand, as well as for areas involved in complex vs. simple hand movements. A standard 1.5 T magne tic resonance imaging (MRT) system has been utilized to localize the cortic al motor hand areas, using the blood oxygen level dependent contrast (BOLDc ) technique and single-section fast low-angle shot (FLASH) imaging. Ten nor mal right-handed subjects volunteered for the study. The motor tasks consis ted of simple (flexion-extension) finger movements of either hand, and comp lex movements (finger-to-thumb opposition in a repeating, pre-planned seque nce) of the non-dominant hand. Simple movements caused contralateral activation of the primary motor area (MA); ipsilateral activation was observed for the non-dominant hand only. S upplementary motor area (SMA) was also activated, with a clear contralatera l prevalence. The ratio of bilateral activation of MA did not change with c omplex movements of the non-dominant hand, while SMA as well as lateral pre motor area were largely bilaterally activated in this task. In conclusion, the ipsilateral MA is activated for movements - even simple - performed wit h the non-dominant hand. There is widespread functional activity, involving both contralateral and ipsilateral SMA, for complex movements.