Neuroplastic Alterations of the Motor Cortex by Caffeine

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.

Conditions

• Cortical Excitability
• Brain Stimulation
• Caffeine

Interventions

OTHER

200 mg caffeine tablet

* 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

OTHER

Non-active tablet

* 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

Sponsors & Collaborators

• University Medical Center Goettingen

  lead OTHER

Principal Investigators

• Walter Paulus · University Medical Center Goettingen, Goettingen

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

45 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2019-07-15

Primary Completion

2019-11-19

Completion

2019-11-19

Countries

• Germany