A new study suggests caffeine may do more than sharpen alertness — it could also influence how the brain processes touch and movement together. Researchers in Denmark found that a typical caffeine dose strengthened a specific brain mechanism linked to motor control, though the effect depended on how it was measured.
That first cup of coffee in the morning may be affecting the brain in ways most people never notice. Beyond boosting focus and reducing drowsiness, caffeine appears to alter how sensory information influences movement inside the brain’s motor system.
The finding comes from new research published in Clinical Neurophysiology, where scientists explored how caffeine changes a neurological process known as short-latency afferent inhibition, or SAI. The process helps regulate how sensations, such as touch, influence muscle activation and movement control.
Researchers say the results offer a closer look at how caffeine interacts with the brain’s communication systems — and why its effects may extend far beyond a temporary energy boost.
Researchers Tested How Caffeine Alters Sensory-Motor Communication
To investigate caffeine’s neurological effects, scientists from Aarhus University Hospital in Denmark recruited 20 healthy adults for a controlled experiment.
Participants received either 200 milligrams of caffeine — roughly equivalent to a common daily intake — or a placebo. Instead of coffee or tablets, the caffeine was delivered through chewing gum to allow faster absorption.
The experiment was conducted as a double-blind study, meaning neither participants nor researchers knew who received caffeine during testing. That design helped reduce bias and strengthened the reliability of the results.
The team focused on SAI, a mechanism in which sensory input temporarily dampens activity in the motor cortex. In practical terms, when the body detects a sensation like touch, the brain slightly reduces motor output to help movements remain controlled and stable.
Without this filtering effect, the nervous system could potentially overreact to constant sensory signals.
Magnetic Brain Stimulation Revealed a Difference
To measure changes in brain activity, researchers used magnetic stimulation on the motor cortex and evaluated participants using two separate techniques.
The first method, called conventional amplitude SAI (A-SAI), used a fixed magnetic pulse and measured the resulting muscle response. The second approach, known as threshold-tracking SAI (T-SAI), continuously adjusted stimulation strength to maintain a consistent muscle reaction.
The difference between the two methods turned out to be important.
Using the conventional A-SAI approach, the researchers found that caffeine increased the brain’s inhibitory response after sensory stimulation. The strongest effects appeared between 19 and 21 milliseconds after stimulation.
However, the second measurement technique showed no significant caffeine-related increase.
The researchers summarized the outcome directly in their paper, writing that caffeine enhanced SAI “as evaluated with the conventional A-SAI protocol, but not with the threshold-tracking method.”
Scientists Believe Adenosine Blocking May Be Responsible
The team believes caffeine’s effects are likely tied to its well-known action on adenosine receptors in the brain.
Adenosine is associated with feelings of tiredness and reduced neural activity. By blocking those receptors, caffeine can increase alertness. But researchers suggest the same mechanism may also influence the brain’s cholinergic system, which relies on the neurotransmitter acetylcholine.
Acetylcholine plays a major role in sensory-motor integration — the process that helps the brain combine incoming sensory information with coordinated movement.
According to the study authors, caffeine’s ability to alter this system could help explain the observed changes in SAI.
The researchers noted that caffeine’s influence “may result from its modulation of the cholinergic system,” adding that the findings could provide insight into both normal brain function and neurological disorders.
The Results Highlight a More Complex Picture of Caffeine
The study does not suggest caffeine dramatically changes movement or behavior in everyday life. Instead, it points to subtle shifts in how the brain processes information between sensation and action.
Importantly, the findings also show that scientific measurements can produce different outcomes depending on the testing method used. One technique detected a measurable effect, while the other did not.
That distinction could matter for future neuroscience research, particularly in studies examining brain signaling and motor control.
The work also reinforces the idea that caffeine is not acting on a single pathway in the brain. Its influence appears to involve multiple interconnected systems tied to alertness, sensory processing, and movement regulation.
Why This Matters
Coffee remains one of the world’s most widely consumed beverages, and caffeine is deeply embedded in daily routines across the globe. Studies like this suggest its effects may be more neurologically complex than many people realize.
By showing that caffeine can alter sensory-motor integration, the research adds another layer to scientists’ understanding of how the brain coordinates movement and responds to sensory input.
The findings may also help researchers better study neurological conditions linked to motor control and cholinergic function. While the study focused only on healthy adults, it opens the door to further investigations into how common substances like caffeine interact with the brain’s communication networks.
For millions of people, coffee may still be about waking up in the morning. But inside the brain, its effects could extend into the systems that quietly shape how humans move through the world.
Study Details
Camilla Carrozzo et al, The effects of caffeine on short-latency afferent inhibition measured with paired-pulse conventional and threshold-tracking TMS, Clinical Neurophysiology (2026). DOI: 10.1016/j.clinph.2026.2111857
