5-Min Science: Your Brain Emits Biophotons

Takeaway

In a remarkable blend of physics and neuroscience, researchers have confirmed that the human brain glows. Not metaphorically—with ideas or thoughts—but literally, with light.

These tiny flashes, known as ultraweak photon emissions (UPEs), are so faint they can’t be seen by the naked eye, but with sensitive detectors, they can now be recorded from outside the skull. Even more intriguingly, the brightness and rhythm of this glow change depending on what your brain is doing.

What is the Science of Biophotons?

Every living cell emits a small amount of light. This is not the showy bioluminescence of a jellyfish or firefly, but a whisper of photons—particles of light—produced as by-products of metabolism. Scientists refer to these ultraweak photon emissions as UPEs. They occur when reactive oxygen molecules, stirred up during the body’s energy production, fall back to their normal state and release a photon in the process. They’re far too dim to see, but they’re there—quiet, continuous, and possibly telling us something important.

This phenomenon isn’t new. It was first hinted at a century ago when Russian scientist Alexander Gurwitsch showed that onion root growth could be blocked by a quartz screen that filtered ultraviolet light, implying that cells might communicate using photons. Later studies confirmed that organisms, from yeast to human skin, emit light, and these emissions can change in response to health, stress, and aging. But the idea that the brain might not just glow but use this glow as part of its signaling has remained speculative—until now.

The brain, as it turns out, is an ideal candidate for light-based investigation. It's metabolically ravenous, filled with mitochondria, and rich in reactive oxygen species, all of which fuel the release of photons. More provocatively, researchers have proposed that certain parts of the brain—such as myelinated axons—could function like biological fiber-optic cables. Non-visual opsins (light-sensitive proteins) and light-absorbing molecules like serotonin are found throughout the brain, raising the possibility that the brain isn’t just emitting light—it might be sensing it too.

Yet despite all this promise, no one had shown that you could measure this light coming from a living, thinking human brain—until this team did.

What Did They Study?

Dr. Nirosha Murugan and her team set out to test a bold idea: that the brain’s light emissions change depending on what it’s doing, and that those changes can be picked up without surgery, implants, or even touching the skin. They wanted to know: does the brain emit photons in ways that reflect thought, attention, or sensory processing? And if so, can we build a new kind of brain scan from that light?

To find out, they invited 20 volunteers into a completely dark room and fitted them with two tools. One was a standard EEG cap to record brainwaves. The other was a set of photomultiplier tubes—exquisitely sensitive detectors capable of counting individual photons. The detectors were aimed at the back and side of the head, near the occipital and temporal lobes, while a third was aimed at a blank wall to capture background light.

Participants cycled through tasks: sitting quietly with eyes open or closed, and listening to a rhythmic sound. These tasks are well-known to change electrical brain activity, particularly in the alpha rhythm range. The question was whether light emissions would shift as well.

How Did They Do It?

The researchers recorded both brainwaves and biophoton emissions simultaneously over 10 minutes. Every 2 minutes, the participant switched tasks: eyes open, eyes closed, music, and back again. The EEG captured fast electrical activity—like alpha waves that increase when eyes are closed—while the light detectors captured photon counts, fluctuations, and rhythms at much slower frequencies.

To analyze these complex data, the team used statistical models and time-frequency analyses. They looked at variability (how much the signal changed over time), entropy (how unpredictable it was), and spectral features (whether the light showed rhythmic bursts). They also compared photon activity from the brain regions to the ambient light detected from the control sensor.

What Did They Find?

The findings were as fascinating as they were unexpected. First, the researchers confirmed that the human brain does, in fact, emit photons that can be measured from outside the head—and these emissions are distinctly different from background light. The brain’s glow was more variable, more complex, and more synchronized across regions than random photons bouncing around a dark room.

Second, these emissions were not constant. They changed depending on the task.

But not everything lined up as expected. In some cases, electrical activity increased in a brain region without a corresponding jump in light.

Sometimes photon emissions appeared to shift even when the EEG didn’t. This mismatch suggests that light and electricity might reflect different dimensions of brain function: one fast and electrical, the other slow and metabolic.

Still, some patterns held. For instance, alpha brainwaves and photon variability increased together during eyes-closed rest, a state of relaxed alertness that requires minimal sensory processing. These findings suggest a potential link between the brain's functioning and its electrical activity, even if the full picture remains incomplete.

What is the Impact?

This study changes our understanding of the brain. It shows, for the first time, that the human brain emits measurable light that changes in response to thought, rest, and sensory input. Whether that light does anything beyond reflect metabolic activity is still unknown. But even as a marker, it’s a game-changer.

If confirmed and refined, this new technique—photoencephalography —could become a powerful complement to EEG and fMRI. It doesn’t require magnetic fields or radioactive tracers. It doesn’t even require physical contact with the body. It’s completely passive and potentially portable. In the future, biophoton imaging might help track brain health, detect early signs of neurodegeneration, or monitor consciousness during sleep and anesthesia.

As it stands, we’ve only just glimpsed this glow. But thanks to this study, we now know it’s there—and changing with every flicker of thought.

Key Takeaways

1. Human brains emit ultraweak light (biophotons), detectable from outside the skull using photomultiplier tubes

2. These emissions differ from background photons in variability, complexity, and rhythmic structure

3. Biophoton patterns change with cognitive tasks but do not mirror EEG signals in a simple, linear fashion

4. The emissions are strongest below 1 Hz, indicating a slow metabolic rhythm distinct from fast electrical oscillations

5. The technique, dubbed "photoencephalography," could supplement traditional brain monitoring and potentially enable new clinical diagnostics

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Glossary

alpha rhythm: a type of brainwave oscillation occurring between 7.5 and 14 Hz, typically associated with relaxed wakefulness and most prominent when the eyes are closed.

bioluminescence: light emission resulting from specific biochemical reactions, such as those involving the enzyme luciferase; distinct from UPEs due to its higher intensity and specialized origin.

biophoton: a photon of light emitted by a biological system as a by-product of oxidative metabolic activity; used interchangeably with ultraweak photon emission (UPE).

coefficient of variation (CV): a standardized measure of signal variability calculated as the ratio of the standard deviation to the mean.

electroencephalography (EEG): a non-invasive technique for recording electrical activity of the brain via electrodes placed on the scalp, capturing oscillations across various frequency bands.

entropy: a measure of the unpredictability or complexity of a signal; higher entropy indicates more informational content and variability.

Fourier transform: a mathematical method for analyzing the frequency content of signals, used in this context to examine rhythmic components of UPEs.

magnetoencephalography (MEG): a neuroimaging technique that records magnetic fields produced by electrical currents in the brain, offering high temporal resolution.

mitochondria: organelles within cells that produce energy through oxidative phosphorylation; a primary source of reactive oxygen species and biophoton emissions.

myelinated axon: a nerve fiber insulated by myelin that increases the speed of electrical conduction and has been theorized to function as an optical waveguide for biophotons.

near-infrared spectroscopy (fNIRS): a neuroimaging method that uses near-infrared light to measure changes in blood oxygenation, often used to infer brain activity.

occipital lobe: the posterior region of the brain primarily responsible for visual processing and a focus of UPE detection in the study.

opsins: light-sensitive proteins found in various tissues, including the brain; non-visual opsins such as OPN3 may respond to biophoton emissions.

photomultiplier tube (PMT): a highly sensitive device capable of detecting single photons; used in this study to measure UPEs from the scalp.

photoencephalography: a proposed brain imaging method that passively records ultraweak light emissions to infer cognitive or metabolic brain states.

radiative decay: the process by which an excited molecule returns to a lower energy state and emits a photon in the process.

reactive oxygen species (ROS): chemically reactive molecules containing oxygen that are produced during metabolism and are key sources of biophoton emissions.

short-time Fourier transform (STFT): a method for analyzing how the frequency content of a signal changes over time; applied here to examine UPE dynamics.

spectral power density (SPD): a measure of the power present in each frequency band of an EEG signal, used to quantify brain oscillatory activity.

temporal lobe: a region of the brain located on the sides of the head involved in auditory processing and another key site for UPE recording.

ultraweak photon emission (UPE): the spontaneous emission of very low-intensity light from living tissue, associated with oxidative metabolic processes and potentially useful as an optical marker of brain activity.

References

Casey, H., DiBerardino, I., Bonzanni, M., Rouleau, N., & Murugan, N. J. (2025). Exploring ultraweak photon emissions as optical markers of brain activity. iScience, 28, 112019. https://doi.org/10.1016/j.isci.2025.112019

Feehly, C. (2025, June 16). Your Brain Is Glowing, and Scientists Can't Figure Out Why. Scientific American. https://www.scientificamerican.com/article/your-brain-is-glowing-and-scientists-cant-figure-out-why/

About the Author

Fred Shaffer earned his PhD in Psychology from Oklahoma State University. He earned BCIA certifications in Biofeedback and HRV Biofeedback. Fred is an Allen Fellow and Professor of Psychology at Truman State University, where has has taught for 50 years. He is a Biological Psychologist who consults and lectures in heart rate variability biofeedback, Physiological Psychology, and Psychopharmacology. Fred helped to edit Evidence-Based Practice in Biofeedback and Neurofeedback (3rd and 4th eds.) and helped to maintain BCIA's certification programs.

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