Somatosensory evoked potentials and high frequency oscillations are differently modulated by theta burst stimulation over primary somatosensory cortex in humans

Abstract

Objective The effects of theta burst stimulation (TBS) have been extensively investigated in primary motor cortex, where it leads to long-lasting LTP/LTD-like effects on synaptic plasticity. This study aimed to extend these observations to sensory cortex. Methods Fourteen healthy subjects participated in the study. Conditioning 600-pulse intermittent TBS (iTBS) and continuous TBS (cTBS) were delivered to left somatosensory cortex (S1) with an intensity of 80% active motor threshold. Somatosensory evoked potentials (SEPs) were evoked by median nerve electrical stimulation at right wrist. High frequency oscillations (HFOs) were obtained by digital filtering of original SEPs and divided into early and late subcomponents, relative to N20 peak latency. Results Repeated-measures ANOVA showed that iTBS facilitated N20 onset–N20 peak at 15 min and N20 peak–P25 at 15 and 30 min after conditioning, whereas cTBS did not. iTBS left the early and late HFOs unchanged. Conversely, cTBS facilitated the early HFOs, whereas it inhibited the late HFOs at 15 min after conditioning. Conclusions S1-iTBS facilitated SEPs without changes in HFOs whereas cTBS modulated early and late HFOs without changes in SEPs. Significance S1-TBS produces lasting changes in the excitability of intracortical circuits generating SEPs and HFOs differentially through mechanisms of LTP/LTD-like synaptic plasticity.