Non-invasive Modulation of Spinal Cord Nociceptive Reflexes

Max Planck Research Group Pain Perception40 enrolled

Overview

The aims of this study are threefold. First, to investigate whether spinal nociceptive processing - represented here by the nociceptive flexion reflex (NFR) - is influenced by thoracic transcutaneous spinal direct current stimulation (tsDCS) in a spatially selective manner, i.e., whether effects are only observed for lower limb NFRs, but not for upper limb NFRs. Second, to investigate - in a double-blind, sham-controlled, within-participant design - whether anodal and cathodal tsDCS do affect the NFR in a polarity-dependent manner. Third, to investigate whether tsDCS effects observed on a spinal measure (NFR) are also observed in responses that are mediated supra-spinally, namely autonomic parameters and pain intensity ratings.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Enrollment

Conditions

Pain

Interventions

tsDCS will be carried out using a direct current stimulator (DC-Stimulator Plus, neuroConn, Ilmenau, Germany), with one electrode placed above the thoracic spinal cord and the other electrode placed on the right shoulder. We will employ rectangular electrodes of 7 x 5 cm size (neuroConn, Ilmenau, Germany) covered by electrode paste (Ten20 Conductive Paste, Weaver and Company, Aurora, USA). Stimulation will consist of the following phases: a fade-in period of 15 seconds, a plateau period of 20 minutes (with stimulation at 2.5mA either anodally or cathodally) and a fade-out period of 15 seconds. Sham stimulation will follow the anodal montage with 15-second fade-in and fade-out periods, but only 45 seconds of plateau stimulation at 2.5 mA. Such a combination of stimulation and electrodes results in a current density of 0.071mA/cm2, well below thermal and histological limits for current density.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 40 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: 1. Healthy volunteers between the ages of 18 and 40 years 2. Having participated in the MRI medical assessment session and consented to taking part in 3T MRI measurements in written form 3. Having participated in the magnetic/electric neurostimulation medical assessment session and consented to taking part in magnetic/electric neurostimulation experiments in written form 4. Voluntary participation and signing of the study-specific consent form Exclusion Criteria: 1. Existence of any contraindications for MRI measurements and magnetic/electric neurostimulation experiments 2. Pregnancy or breastfeeding 3. Very dry or sensitive skin (e.g., intolerance to creams/shampoos) 4. Chronic skin diseases - such as eczema or neurodermatitis - in the area of somatosensory / nociceptive stimulation (arm or hand, leg or foot) or electrophysiological data recording (upper body, arm, leg) 5. Scar tissue in the area of somatosensory / nociceptive stimulation (arm or hand, leg or foot) or electrophysiological data recording (upper body, arm, leg) 6. Acute sunburn in the area of somatosensory / nociceptive stimulation (arm or hand, leg or foot) or electrophysiological data recording (upper body, arm, leg) 7. Current or recurring pain 8. Injuries to the nervous system 9. History of or current neurological or psychiatric disorders 10. Chronic diseases that require permanent medication (e.g., asthma, diabetes mellitus, etc.) 11. Persons not capable of giving consent (e.g., in case of dementia) 12. Lack of consent with regards to report of incidental findings