Transcranial Versus Suboccipital Direct Current Stimulation
Condition: Pain; Transcranial Direct Current Stimulation
Study type: Interventional

Summary: 
      Randomized controlled trial, in parallel with cross-control design. Two groups of healthy
      subjects will be randomly selected to transcranial stimulation group or suboccipital
      stimulation group. Each group receive in a randomized order a real direct current session and
      a sham session. The study is based on the hypothesis that the application of direct current
      sitmulation applied at the suboccipital level produce higher modifications on endogenous pain
      modulation system than transcranial stimulation.
    

Detailed description: 
      The development of the project will be based on the Declarations of the World Medical
      Association of Helsinki. Every subject will be informed about the nature of the study,
      willingness to participate, the proposed objectives, as well as possible adverse effects that
      may occur in its implementation. Every subject will be asked to give their signed consent to
      participate in the study. The study will be suspended at any time, if the patient wishes.

      Healthy volunteers will be recruited from the city of Toledo, between the ages of 18 and 40.
      The detection and selection of the sample will be carried out between the students of the
      University of Castilla-La Mancha and personnel of the Hospital Nacional de Parapléjicos who
      meet the inclusion criteria and give their consent voluntarily to participate in the study.

      The calculation of the sample size will be carried out using the G * Power software program
      (version 3.1), for clinical studies with two intervention groups. Conditioned pain modulation
      will be chosen as the primary outcome variable. Assuming an α level of 0.05 and a statistical
      power of 85%, with a moderate effect size for the ANOVA test (0.25).

      The experiment will be carried out in the clinical laboratory of the Sensory-Motor Function
      Research Group of the Hospital Nacional de Parapléjicos. Under attenuated sound conditions,
      and at a stable temperature in the range of (22 °C-26 °C).

      In the first session of the study, a small interview will be carried out to determine if
      there is any exclusion criterion. The initial measurements will consist of sociodemographic
      variables and psychological variables, which will then be used to categorize groups and
      analyze covariates. A parallel randomized controlled trial with cross-control design is
      proposed. Two groups of healthy subjects will be randomly selected to transcranial direct
      current stimulation (DCS) group or suboccipital DCS group. Each group receive in a randomized
      order and with a double blind design a real direct current session and a sham session. An
      assessment is made before and after each intervention.

      Subjects will remain in a sitting position, with their backs resting in a relaxed position.
      In all interventions a direct current stimulator (DC-stimulator, Neuroconn) will be used.
    

Intervention name(s): Direct Current Stimulation; Sham DCS
Intervention type(s): Device; Device
Intervention description(s): 20 minutes of direct current stimulation using an intensity of 1.5mA and electrode size of 6x4cm; 20 minutes of sham stimulation. Subjects will be stimulated during the first 30 seconds. After that, a ramp down of 10 seconds and then the stimulator is turned-off.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Paralled randomized controlled trial with cross-control design. Two groups of subjects will be randomly selected, a Transcranial stimulation group and a suboccipital stimulation group. Each group will perform two intervention sessions in a randomized order, a session with direct current stimulation and a sham stimulation session.
Masking: Double (Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Direct Current Stimulation; Conditioned Pain Modulation; Endogenous Pain Modulation; Temporal Summation; Pressure Pain Threshold; Pain