Hemispheric asymmetry and somatotopy of afferent inhibition in healthy humans

There are hemispheric asymmetries of the primary motor cortices (M1) in humans thought to be related to handedness. Whether this is also true for interactions between the somatosensory and the motor cortex is unclear. We thus investigated sensory-motor interactions over both hemispheres in right hander using conditioning electrical pulses of 3 times of the sensory threshold applied to the right or left index finger and transcranial magnetic stimulation (TMS) test pulses given over the corresponding M1 (afferent inhibition; AI). Typically, conditioning electrical pulses suppress motor evoked potentials (MEP) foll…