Effects of paired associative stimulation and repetitive transcranial magnetic stimulation on the excitability of the motor cortex / 中华物理医学与康复杂志

ABSTRACT

Objective To compare the effects of paired associative stimulation (PAS) and repetitive transcranial magnetic stimulation (rTMS) on motor cortex excitability.Methods The baseline corticospinal excitability of the left hemispheres of 10 healthy subjects was measured in terms of resting motor threshold (RMT) and other indicators of motor evoked potentials (MEP).On the following day they received PAS composed of trascranial magnetic stimulation (TMS) to the motor cortex of the left hemisphere and electric stimulation (ES) of the median nerve contralateral to the motor cortex,with an interval of 10ms between the TMS and ES (termed PAS10).The PAS10 was delivered at a frequency of 0.05 Hz and an intensity of 120％ of the RMT,for a total of 90 pulses.The MEP amplitude,MEP latency and RMT were evaluated one minute after the stimulation.After the PAS intervention,an interval of one week was allowed to eliminate any effect of PAS on motor cortex excitability.Then rTMS was delivered to the subjects' left motor cortex at the same time of day at a frequency of 1 Hz and an intensity of 120％ of the RMT,for a total of 1000 pulses.MEP amplitude,MEP latency and RMT were evaluated one minute after the stimulation.The two interventions were compared in terms of MEP amplitude,MEP latency and RMT.Results The average MEP amplitude,MEP latency and RMT at baseline were (2.93 ± 0.99) mV,(20.97 ± 1.67) ms,and (46.06 ±5.32) ％,respectively.One minute after PAS10,the MEP amplitude,MEP latency and RMT were (1.14 ± 0.76) mV,(21.87 ± 1.09) ms and (52.06 ±4.20) ％,respectively.One minute after rTMS,the MEP amplitude and latency and the RMT were (2.24 ± 0.79) mV,(20.88 ± 1.94) ms,and (49.00 ± 4.54) ％,respectively.The differences in MEP amplitude,MEP latency and RMT pre-and post-intervention were (0.69 ± 0.10) mV,(0.09 ±0.05) ms and (3.94 ± 0.93) ％,respectively for rTMS.For PAS10 they were (1.83 ± 0.14) mV,(0.90 ± 0.26)ms and (6.00 ± 1.13)％,respectively.The differences in MEP amplitude decrease and MEP latency lengthening between the two stimulation protocols were significant,but the difference in RMT elevation was not.Conclusion Both PAS10 and low frequency rTMS suppressed motor cortex excitability,but the suppressive effect of PAS10 is more significant.