“…This rationale is based on short-latency, likely mono-synaptic excitatory input from SMA-proper to M1 corticospinal neurons (peaking at 2 ms and 4 -6 ms) in monkey intracortical microstimulation experiments (Tokuno and Nambu, 2000) and paired-coil experiments from our group, which showed MEP facilitation if stimulation of SMA-proper preceded a TMS test pulse over M1 by 6 ms (N. Arai, M.-K. Lu, Y. Ugawa, and U. Ziemann, unpublished data). The ISIs of Ϫ3.2 ms and ϩ10 ms were selected because conventional PAS experiments pairing electrical peripheral nerve stimulation with TMS of the contralateral M1 or primary somatosensory cortex had demonstrated a steep transition from a maximum long-term facilitation to maximum depression within a time window of 15-20 ms (Wolters et al, 2003(Wolters et al, , 2005. If this time window also applied to PAS-induced plasticity in the SMA-M1 network, then these intervals, which are intermediate to Ϫ6 ms and ϩ15 ms, should be less effective in inducing long-term MEP change.…”