Analysis of correlation between the recruitment of excitation and inhibition in the motor cortex

The size of motor evoked potentials (MEP) and the duration of the silent period (SP) in active muscles correlate although they represent different aspects of the modulation of motor cortical excitability. Little is known,however, whether there is also a correlation between the MEP and SP recruitment. The stimulus-response curves for MEPs and SP were constructed by using transcranial magnetic stimulation (TMS) over the motor cortex in small hand muscles of 15 healthy volunteers (mean age 25.2). MEP and SP recruitment curves (MEP- and SP-RC) were constructed by applying 10 stimuli randomly in steps of 10% between…