iTBS-induced LTP-like plasticity parallels oscillatory activity changes in the primary sensory and motor areas of macaque monkeys

PLoS One. 2014 Nov 10;9(11):e112504. doi: 10.1371/journal.pone.0112504. eCollection 2014.

Abstract

Recently, neuromodulation techniques based on the use of repetitive transcranial magnetic stimulation (rTMS) have been proposed as a non-invasive and efficient method to induce in vivo long-term potentiation (LTP)-like aftereffects. However, the exact impact of rTMS-induced perturbations on the dynamics of neuronal population activity is not well understood. Here, in two monkeys, we examine changes in the oscillatory activity of the sensorimotor cortex following an intermittent theta burst stimulation (iTBS) protocol. We first probed iTBS modulatory effects by testing the iTBS-induced facilitation of somatosensory evoked potentials (SEP). Then, we examined the frequency information of the electrocorticographic signal, obtained using a custom-made miniaturised multi-electrode array for electrocorticography, after real or sham iTBS. We observed that iTBS induced facilitation of SEPs and influenced spectral components of the signal, in both animals. The latter effect was more prominent on the θ band (4-8 Hz) and the high γ band (55-90 Hz), de-potentiated and potentiated respectively. We additionally found that the multi-electrode array uniformity of β (13-26 Hz) and high γ bands were also afflicted by iTBS. Our study suggests that enhanced cortical excitability promoted by iTBS parallels a dynamic reorganisation of the interested neural network. The effect in the γ band suggests a transient local modulation, possibly at the level of synaptic strength in interneurons. The effect in the θ band suggests the disruption of temporal coordination on larger spatial scales.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Electrocorticography
  • Evoked Potentials, Somatosensory*
  • Macaca mulatta / physiology*
  • Models, Animal
  • Sensorimotor Cortex / physiology*
  • Theta Rhythm / physiology
  • Transcranial Magnetic Stimulation / methods

Grants and funding

OP was supported by a doctoral fellowship of the Sapienza University in Neurophysiology. PDG, SF and VD were supported by the ISS-USA project “Brain reorganization under cortical stimulation - BRUCOS”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.