Neuroplastic Alterations of the Motor Cortex by Caffeine
Condition: Cortical Excitability; Brain Stimulation; Caffeine
Study type: Interventional

Summary: 
      Caffeine is a psychostimulant drug. It acts as a competitive antagonist at adenosine
      receptors, which modulate cortical excitability as well. In deep brain stimulation (DBS), the
      production of adenosine following the release of adenosine triphosphate (ATP) explains the
      reduction of tremor. Binding of adenosine to adenosine A1 receptors suppresses excitatory
      transmission in the thalamus and hereby 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.

      Based on this finding, the investigators hypothesize that the antagonistic effect of caffeine
      can tentatively block the excitatory effects of transcranial alternating current stimulation
      (tACS). The plasticity effects might differ among caffeine users and non- caffeine users
      depending on the availability of receptor binding sites.

      Apart from that, a major issue in NIBS studies including those studying motor-evoked
      potentials is the response variability both within and between individuals. The trial to
      trial variability of motor evoked potentials (MEPs) may be affected by many factors. Inherent
      to caffeine is its effect on vigilance. In this study, the investigator shall monitor the
      participant's vigilance by pupillometry to (1) better understand the factors, which might
      cause variability in transcranial excitability induction studies and (2) to separate the
      direct pharmacological effect from the indirect attentional effect of caffeine.
    


Intervention name(s): 200 mg caffeine tablet; Non-active tablet
Intervention type(s): Other; Other
Intervention description(s): Transcranial alternating current stimulation (140 Hz tACS) at 1 mA and active vigilance condition
Transcranial alternating current stimulation (140 Hz tACS) at 1 mA and passive vigilance condition
Transcranial alternating current stimulation (140 Hz tACS) sham and active vigilance condition
Transcranial alternating current stimulation (140 Hz tACS) sham and passive vigilance condition; Transcranial alternating current stimulation (140 Hz tACS) at 1 mA and active vigilance condition
Transcranial alternating current stimulation (140 Hz tACS) at 1 mA and passive vigilance condition
Transcranial alternating current stimulation (140 Hz tACS) sham and active vigilance condition
Transcranial alternating current stimulation (140 Hz tACS) sham and passive vigilance condition
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
Keywords: Plasticity; Variability; Non-invasive brain stimulation; Caffeine