Facilitation of Early and Middle Latency SEP after tDCS of M1: No Evidence of Primary Somatosensory Homeostatic Plasticity

Daniela M Zolezzi; Dennis B Larsen; Anna M Zamorano; Thomas Graven-Nielsen

doi:10.1016/j.neuroscience.2024.05.001

Facilitation of Early and Middle Latency SEP after tDCS of M1: No Evidence of Primary Somatosensory Homeostatic Plasticity

Neuroscience. 2024 May 11:S0306-4522(24)00187-8. doi: 10.1016/j.neuroscience.2024.05.001. Online ahead of print.

Authors

Daniela M Zolezzi¹, Dennis B Larsen¹, Anna M Zamorano¹, Thomas Graven-Nielsen²

Affiliations

¹ Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
² Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark. Electronic address: tgn@hst.aau.dk.

PMID: 38735429
DOI: 10.1016/j.neuroscience.2024.05.001

Abstract

Homeostatic plasticity is a mechanism that stabilizes cortical excitability within a physiological range. Most homeostatic plasticity protocols have primed and tested the homeostatic response of the primary motor cortex (M1). This study investigated if a homeostatic response could be recorded from the primary sensory cortex (S1) after inducing homeostatic plasticity in M1. In 31 healthy participants, homeostatic plasticity was induced over M1 with a priming and testing block of transcranial direct current stimulation (tDCS) in two different sessions (anodal and cathodal). S1 excitability was assessed by early (N20, P25) and middle-latency (N33-P45) somatosensory evoked potentials (SEP) extracted from 4 electrodes (CP5, CP3, P5, P3). Baseline and post-measures (post-priming, 0-min, 10-min, and 20-min after homeostatic induction) were taken. Anodal M1 homeostatic plasticity induction significantly facilitated the N20-P25, P45 peak, and N33-P45 early SEP components up to 20-min post-induction, without any indication of a homeostatic response (i.e., reduced SEP). Cathodal homeostatic induction did not induce any significant effect on early or middle latency SEPs. M1 homeostatic plasticity induction by anodal stimulation protocol to the primary motor cortex did not induce a homeostatic response in SEPs.

Keywords: homeostatic plasticity; primary motor cortex; primary sensory cortex; somatosensory evoked potentials; transcranial direct current stimulation.