Coffee could be slowly changing how the brain responds to touch and one’s own body movements, a small new study suggests.
Millions worldwide take a cup of coffee in the morning to increase wakefulness, alleviate fatigue, and improve concentration and focus.
Normal doses of about a cup or two of daily coffee have between 50 and 400 mg of its active ingredient caffeine.
Exactly how higher doses of coffee affect the brain’s perception of touch remains less studied.
Now, a new study has assessed how normal and high doses of caffeine affect a specific brain process.
This brain process is assessed using a method called short-latency afferent inhibition (SAI), in which a mild electrical shock is sent to the wrist shortly before sending a magnetic pulse into the brain.
The sensory signal from the wrist travels up the arm and enters the brain’s somatosensory area, and milliseconds later, the magnetic pulse hits the nearby motor cortex to trigger a thumb twitch.
To suppress the twitch, the brain typically requires a coordinated effort among specific chemical messengers in the brain.
This brain process typically acts as a filtering system to keep movements smooth and controlled, preventing the brain from overreacting to every single touch.
In the latest study, researchers assessed this filtering process in 20 healthy adults, who received either 200mg of caffeine or a placebo.
Scientists stimulated the motor cortex of the patients with magnetic pulses using a non-invasive method, and then measured how their brains reacted.
They found that caffeine increased the brain's ability to restrict muscle response after a touch, indicating that coffee could “enhance SAI”.
Scientists suspect caffeine acts by blocking adenosine receptor proteins in the brain.
Blocking of the receptors could lead to an increase in acetylcholine, a chemical messenger that helps control how our senses and muscle movement work together.
“This finding aligns with findings that cholinergic-enhancing drugs like donepezil also enhance SAI,” researchers wrote.
"Caffeine's effect may result from its modulation of the cholinergic system,” scientists wrote, adding that the findings offer insights into the drug’s physiological action and how it may be tied to disorders like Alzheimer’s and Parkinson’s.
Scientists hope to conduct further studies with more participants, using more than 400 mg of caffeine.
“In light of the results discussed so far, subjects should continue to abstain from caffeine before SAI examinations,” they concluded.
