Cheng-Ta Li, Chi-Hung Juan, Tung-Ping Su, Ying-Jay Liou, Mu-Hong Chen, Chih-Ming Cheng and Ying-Zu Huang
Objective: Transcranial Magnetic Stimulation (TMS) has become a widely used and excellent method for examining cortical excitability abnormalities in the human system. However, the direct link between TMS measurements and its representation of regional neural brain activity is yet to be determined. We hypothesize that TMS parameter measurements of the motor cortices of both the dominant-side and non-dominant side would reflect direct correlations with their respective regional neural activities of the targeted motor cortex. Methods: Twenty-Seven right-handed subjects were recruited under the Edinburgh Handedness Inventory. All subjects were healthy, and were exposed to excitatory and inhibitory TMS pulses from the bilateral motor cortices and brain glucose metabolism. Brain glucose metabolism was measured by 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) at rest. Results: All procedures were well tolerated with no adverse events. The voxel-wise analysis demonstrated significant relationship between the dominant-side TMS parameters (including resting motor threshold, motor evoked potentials (MEP) amplitude, along with long interval intra-cortical inhibition) with the dominant-side motor related areas (family-wise errors-corrected p<0.005). In contrast to this finding, our study found that TMS measurements from the non-dominant side were connected to areas beyond the non-dominant-side motor areas in both hemispheres. Conclusion: TMS parameters from the dominant-side motor cortices better represent target motor cortex and their regional neural activities. Significance: This study finds variation in stimulation parameters measured from the different bilateral motor cortices.
