Gamma-band connectivity is reduced in schizophrenia following prefrontal TMS and during working memory

Abstract

s / Brain Stimulation 8 (2015) 360e377 365 NIBS is large interand intra-subject variability in NIBS-induced neuroplastic responses. We investigated (1) the reproducibility of neuroplastic responses induced by continuous theta-burst stimulation (cTBS) and (2) factors that can influence an individual’s neuroplasticity response to cTBS. In 18 subjects, motor evoked potential (MEP) input-output (I/O) curves were obtained before and after cTBS (3 stimuli at 50 Hz every 200 msec for 40 sec) and measures of physical activity levels, stress levels, and sleep patterns were obtained in three separate experimental sessions. MEP suppression was observed following cTBS at the upper end of the IO curve (150 e 180% RMT). Significant linear relationships were evident between (1) cTBS-induced MEP suppression (probed at 150% RMT) and perceived stress and (2) cTBS-induced MEP suppression (probed at the stimulus intensity that evoked a MEPw50% of the maximal MEP; SI50) and the interval between experimental sessions (in days). The current data suggest (1) the most reliable TMS intensity to probe cTBS-induced neuroplastic responses is 150% RMT; (2) the perceived stress scale is sufficiently sensitive to show the positive relationship between stress and long-term depression-like plasticity; (3) short intervals between experimental sessions administering NIBS protocols is associated with increased NIBS-induced plasticity responses.