Modulating Pain Using Transcranial Alternating Stimulation (tACS) in Healthy Human Subjects
Condition: Experimental Pain in Healthy Human Subjects
Study type: Interventional

Summary: 
      Pain is a highly complex and subjective phenomenon which results from the dynamic integration
      of sensory and contextual (i.e. cognitive, emotional, and motivational) processes. Recent
      evidence suggests that neural oscillations and their synchronization between different brain
      areas might form the basis of these integrative functions. When investigating tonic
      experimental pain lasting for several minutes, for example, objective stimulus intensity is
      inversely related to alpha (8-13 Hz) and beta (13-30 Hz) oscillations in early somatosensory
      areas, while subjective pain intensity is positively associated with gamma (30-100 Hz)
      oscillations in prefrontal cortex. Yet, with a few exemptions, reported links between
      oscillatory brain activity and pain have mostly been established by correlative approaches
      which do not allow to infer causality. The current project aims at comprehensively
      investigating the causal role of neural oscillations for tonic experimental pain in healthy
      human subjects. To this end, transcranial alternating current stimulation (tACS) will be
      employed to modulate oscillatory brain activity in alpha and gamma frequency bands and
      investigate effects of this manipulation on pain perception and pain-related autonomic
      responses. Using an established tonic pain stimulation protocol and a double-blind,
      sham-controlled design, effects of tACS of somatosensory as well as prefrontal brain areas
      will be investigated. Results promise to elucidate the neural mechanisms underlying tonic
      experimental pain by testing the mechanistic role of neural oscillations in different aspects
      of pain processing. Furthermore, they might contribute to the development of urgently needed
      new treatment approaches for chronic pain using neuromodulatory methods.
    


Intervention name(s): 10 Hz tACS of the bilateral somatosensory cortex; 10 Hz tACS of the prefrontal cortex; 80 Hz tACS of the bilateral somatosensory cortex; 80 Hz tACS of the prefrontal cortex; Sham stimulation of the bilateral somatosensory cortex; Sham stimulation of the prefrontal cortex
Intervention type(s): Device; Device; Device; Device; Device; Device
Intervention description(s): 10 Hz tACS at 1 mA will be applied over the bilateral somatosensory cortex for 10 minutes using a Neuroconn stimulator (DC-Stimulator MR; Neuroconn, Ilmenau, Germany) and 2 5*5 cm rubber electrodes placed at electrode positions CP3 and CP4 according to the international 10-20 system.; 10 Hz tACS at 1 mA will be applied over the prefrontal cortex for 10 minutes using a Neuroconn stimulator (DC-Stimulator MR; Neuroconn, Ilmenau, Germany) and 2 5*5 cm rubber electrodes placed at electrode positions F3 and F4 according to the international 10-20 system.; 80 Hz tACS at 1 mA will be applied over the bilateral somatosensory cortex for 10 minutes using a Neuroconn stimulator (DC-Stimulator MR; Neuroconn, Ilmenau, Germany) and 2 5*5 cm rubber electrodes placed at electrode positions CP3 and CP4 according to the international 10-20 system.; 80 Hz tACS at 1 mA will be applied over the prefrontal cortex for 10 minutes using a Neuroconn stimulator (DC-Stimulator MR; Neuroconn, Ilmenau, Germany) and 2 5*5 cm rubber electrodes placed at electrode positions F3 and F4 according to the international 10-20 system.; 10 Hz tACS at 1 mA will be applied over the bilateral somatosensory cortex for 10 seconds at the beginning of the experimental session using a Neuroconn stimulator (DC-Stimulator MR; Neuroconn, Ilmenau, Germany) and 2 5*5 cm rubber electrodes placed at electrode positions CP3 and CP4 according to the international 10-20 system.; 10 Hz tACS at 1 mA will be applied over the prefrontal cortex for 10 seconds at the beginning of the experimental session using a Neuroconn stimulator (DC-Stimulator MR; Neuroconn, Ilmenau, Germany) and 2 5*5 cm rubber placed at electrode positions F3 and F4 according to the international 10-20 system.
Intervention model: Single Group Assignment
Intervention model description: Each participant will participate in 6 experimental conditions aimed at studying the effect of different tACS protocols on pain processing: (1) 10 Hz tACS of the bilateral somatosensory cortex, (2) 10 Hz tACS of the prefrontal cortex, (3) 80 Hz tACS of the bilateral somatosensory cortex, (4) 80 Hz tACS of the prefrontal cortex, (5) sham stimulation of the bilateral somatosensory cortex, and (6) sham stimulation of the prefrontal cortex. Each condition will be administered in an individual session. Sessions will be conducted in pseudo-randomized order and separated by at least 24 hours to avoid any carry-over effects of the stimulation. During each tACS administration, pain will be induced by means of an established tonic thermal stimulation paradigm lasting for several minutes (TSA-II; Medoc, Ramat Yishai, Israel) while pain ratings and autonomic responses will be recorded (Nickel et al., 2017a; Nickel et al., 2017b).
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: pain; tACS; alpha; gamma; neural oscillations; brain