Cortical Excitability Changes on the Sensorimotor Cortex Induced by Caffeine Consumption: A TMS Study
Condition: Cortical Excitability; Brain Stimulation
Study type: Interventional

Summary: 
      Caffeine is a widely used psychostimulant drug and acts as a competitive antagonist at
      adenosine receptors. Its effect is on neurons and glial cells of all brain areas. Chronic
      consumption of caffeine leads to tolerance which might be associated with an increased number
      of binding sites in the brain. In deep brain stimulation (DBS), the production of adenosine
      following the release of adenosine triphosphate (ATP) explains the reduction of in tremor.
      Binding of adenosine to adenosine A1 receptor suppresses excitatory transmission in the
      thalamus and thus reduces both tremor-and DBS-induced side effects. Also, the effect of
      adenosine was attenuated following the administration of the
      8-Cyclopentyl-1,3-dipropylxanthine (DPCPX) adenosine A1 receptor antagonist. Therefore, the
      presence of a receptor antagonist such as caffeine was suggested to reduce the effectiveness
      of deep brain stimulation (DBS) in treating tremor and other movement disorders.

      In light with this finding, we anticipate that the antagonistic effect of caffeine is a
      culprit to the reduction of effectiveness of any stimulation protocol in non-invasive
      stimulation (NIBS). In particular the excitatory effects of a NIBS protocol can tentatively
      be blocked in the presence of caffeine.

      In this study, the effects of caffeine consumption on cortical excitability at the
      sensorimotor cortex shall be examined on focal and non-focal plasticity. Focal plasticity
      will be induced by paired associated stimulation (PAS) and global cortical plasticity from
      transcranial alternating current (tACS) stimulation. In case of tACS stimulation, 1) an
      excitatory protocol (tACS, 140 Hz, 1 mA) and 2) an inhibitory protocol (tACS, 140 Hz, 0.4 mA)
      with the active electrode over M1 and the return electrode over the orbitofrontal cortex will
      be used. Changes in cortical excitability are assessed using transcranial magnetic
      stimulation (TMS) recordings.

      Research goals are to examine the effects of caffeine consumption on sensorimotor cortical
      excitability and stimulation induced plasticity. In addition, this study explores further
      factors which usually contribute to variability in cortical excitability studies. The results
      are expected to give a useful recommendation for researchers to reduce confounding factors
      and hereby improves repeatability.
    


Intervention name(s): Caffeine_TMS
Intervention type(s): Combination Product
Intervention description(s): Caffeine group: participants will receive a caffeine tablet and all electrical stimulations in a random order [transcranial electrical stimulation (tACS 140 Hz at 1 mA, 0.4 mA, sham) and paired associative stimulation (PAS 25)] Placebo tablet: participants will receive a placebo tablet and all electrical stimulations in a random order [transcranial electrical stimulation (tACS 140 Hz at 1 mA, 0.4 mA, sham) and paired associative stimulation (PAS 25)]
Intervention MeSH terms: Caffeine
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: 15 participants are assigned to caffeine group and another 15 are assigned to placebo group. Then, the participants who were initially in the caffeine group now be in placebo group and those who were in the placebo group were assigned to caffeine group. Finally, all participants received both placebo and caffeine
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science