Interaction between repetition suppression in motor activation and long-interval intracortical inhibition

Sci Rep. 2019 Aug 8;9(1):11543. doi: 10.1038/s41598-019-47932-9.

Abstract

Repetition suppression (RS) is the adaptation of the neural activity in response to a repeated external stimulus. It has been proposed that RS occurs at the thalamo-cortical level, hence activating a feedback loop to the cortex in order to counteract with the repeated motor cortical activation. In this study, to elucidate the common modulators between the RS and the inhibitory/facilitatory cortical networks, two TMS paradigms were applied, i.e. the characteristic long-interval intracortical inhibition (LICI) and the I1-wave timed short-interval intracortical facilitation (SICF). Since LICI is a local intracortical inhibitory phenomenon affecting cortical excitation over a long interval like the RS, the interaction between RS and LICI was tested. As the I1-wave timed SICF is likely not affected by inhibitory modulation, the appearance of the RS with respect to SICF was investigated. Non-linear interaction between LICI and RS was observed, while I1-wave timed SICF facilitated all MEP responses of RS by a common offset still preserving the RS. These findings implicate that the underlying mechanism for the observed interaction is likely contributed to the activation of the negative thalamo-cortical feedback loop represented by the RS, most likely at the cortical level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Electromyography / methods
  • Evoked Potentials, Motor / physiology*
  • Humans
  • Inhibition, Psychological
  • Male
  • Motor Cortex / diagnostic imaging
  • Motor Cortex / physiology*
  • Neural Inhibition / physiology*
  • Thalamus / diagnostic imaging
  • Thalamus / physiology*
  • Transcranial Magnetic Stimulation