BACKGROUND:Functional MRI(fMRI)demonstrates the localization of hand representation in the motor cortex,thereby providing feasible noninvasive mapping of functional activities in the human brain.OBJECTIVE:To observe cortical activation within different cortical motor regions during repetitive hand movements in healthy subjects through the use of fMRI.DESIGN:An observational study,with each subject acting as his own control.SETTING:Department of Radiology,the First Affiliated Hospital of Nanchang University.PARTICIPANTS:Seven healthy volunteers,4 males and 3/females,aged 19 to 38 years,participated in the study.All subjects were right-handed,with no neurological or psychological disorders.Informed written consent was obtained from all subjects,and the study was approved by the Institutional Review Board of the First Affiliated Hospital of Nanchang University.METHODS:The study was performed at the Department of Radiology between June-August 2005.A 1.5 Tesla Siemens MRI scanner(Symphony,Germany)was used to acquire Tl-weighted structural images,which were oriented parallel to the line running through the anterior and the posterior commissures.Subjects were instructed on a task and were allowed to practice briefly prior to the imaging procedure.The motor activation task consisted of the right hand performing a clenching movement.The T1-W images were acquired from six alternating epochs of rest and activation from all seven healthy subjects.Data were collected with echoplanar imaging of brain oxygen level dependent(BOLD)sequence.Each series comprised six cycles of task pertormance(30 seconds),alternating with rest(30 seconds) periods,and 3-second time intervals.The differences between active and baseline fMRI imaging were calculated using the student t-test.Differential maps were overlaid on the high resolution T1-W structural image for neuroanatomical correlation of activation areas.MAIN OUTCOME MEASURES:The omega-shaped hand knobs were recognized on T1-W structural images.Active signal changes in the primary(M1)and secondary motor(M2)areas,as well as the relationship between the hand knobs and M1 area activation,were analyzed.Region of interest was selected for signal change quantitative graphic analysis.RESULTS:All 7 enrolled volunteers were included in the final analysis.In the present study,hand knob structures were recognized on Tl-weighted images in all subjects and were omega-shaped in the axial plane.Significant functional activations were observed in the contralateral primary motor area of all subjects. Activation signals were distributed mainly in the central sulcus around the hand knob.The contralateral primary sensory(S1)cortex was activated in most cases,and ipsilateral M1 was activated in 3 subjects. Contralateral or bilateral supplementary motor area(SMA)was also activated in 6 cases.Premotor area,or super parietal lobe,was activated in two subjects.Three-dimensional reconstruction demonstrated that the active signal of M1 was primarily located at the middle-lateral surface of the contralateral precentral gyrus in Brodmans area 4,and the signal of SMA activation was located in the mesial surface of the premotor area. CONCLUSION:The knob structure of the precentral gyrus is the representative motor area for hand movement.The cerebral cortical motor network was extensively activated during voluntary hand movements in normal subjects.In alert,conscious human subjects,the activated fMRI signal safely and non-invasively localized and lateralized the motor cortical activity associated with simple voluntary repetitive hand movements.Whether higher cognitive functions,such as perception and speech,can be similarly mapped using the fMRI technique and the BOLD method remains to be determined in future well-designed human studies.