Maturation of short-interval inhibitory and excitatory circuits in the human primary motor cortex

s / Brain Stimulation 8 (2015) 360e377 372 spasticity in 4 post-stroke subjects that affected tonic stretch reflex threshold (TSRT) [2], i.e., the joint angle at which the stretch reflex begins to act due to the descending and segmental influences on motoneurons. The rectangular (4.5 cm 9 cm) electrodes were placed on each side of the spine (5 cm apart) over the paravertebral skin at the twelfth thoracic and first lumbar vertebral levels [3]. We found that only the high frequency (2100 Hz) sinusoidal stimulation (HFSS) and not the low frequency sinusoidal stimulation (LFSS) (20Hz) significantly affected the TSRT during tsACS application (45mins). LFSS showed significant aftereffects only after 45mins of tsACS application. Therefore, HFSS and LFSS may involve different mechanisms based on the ion channel distributions and their response properties in the neural tissue of the dorsal column [1].