Does caffeine modify corticomotor excitability?

Neurophysiol Clin. 2006 Jul-Aug;36(4):219-26. doi: 10.1016/j.neucli.2006.08.005. Epub 2006 Aug 22.


Aims: To test the influence of caffeine on the lower and upper motor neuron excitability.

Methods: In Experiment A, 18 healthy subjects received 200 mg of caffeine or placebo, in a randomized, double-blind, placebo-controlled design protocol. Mean F-waves amplitude, amplitude of the motor response evoked by magnetic stimulation (MEP), MEP duration, cortical silent period (CSP), central conduction time, and cortical threshold were evaluated. In Experiment B, 6 healthy controls received 400 mg of caffeine, the peripheral silent period (PSP) and CSP were evaluated. CSP was recorded bilaterally in biceps brachii (intensity 10% above threshold) and abductor digiti minimi (ADM) (intensity at 10% and 50% above threshold). Muscle contraction was above 50% of the maximum force in both experiments. Latencies were defined by a technician who was not aware of this investigation. Serum caffeine level was evaluated.

Results: In Experiment A, only the CSP, recorded in both ADM with intensity at 10% above threshold showed a significant change after caffeine (decrease of 17.1+/-34.0 ms, about 12% reduction). In Experiment B, PSP did not change, but CSP tested with intensities 10% above threshold was significantly decreased by 20.8+/-34.4 ms in ADM and 13.5+/-13.8 ms in biceps (about 13 and 16%, respectively). Serum caffeine level clearly increased after consumption but no correlation could be found between these levels and CSP reduction.

Conclusions: In our investigation, caffeine elicited a consistent decrease of the CSP, suggesting that caffeine increases cortical neuronal excitability.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Caffeine / blood
  • Caffeine / pharmacology*
  • Central Nervous System Stimulants / blood
  • Central Nervous System Stimulants / pharmacology*
  • Double-Blind Method
  • Electroencephalography / drug effects
  • Electromagnetic Fields
  • Evoked Potentials, Motor / physiology
  • Female
  • Humans
  • Male
  • Motor Cortex / drug effects*
  • Motor Neurons / drug effects*
  • Muscle, Skeletal / innervation
  • Muscle, Skeletal / physiology
  • Peripheral Nerves / drug effects
  • Peripheral Nerves / physiology
  • Spinal Cord / cytology
  • Spinal Cord / drug effects
  • Stimulation, Chemical
  • Transcranial Magnetic Stimulation


  • Central Nervous System Stimulants
  • Caffeine