Brain Emits Light Through Skull, According to a New Study

Scientists have discovered that the human brain emits weak light signals that can be registered regardless of external lighting.

Scientists have found out how exactly these signals are related to mental state and whether they can be used to monitor brain activity. The results of the study are published in the journal iScience.

All living tissues emit very weak photon radiation during metabolism. This light is not like bioluminescence, where light is emitted as a result of chemical reactions.

In the case of ultra-weak photon radiation, light is produced when molecules transition from an excited state to a calmer state, and its intensity is extremely low – about a million times weaker than the light visible to the eye.

The brain emits more of this radiation than other organs, which is due to its high energy consumption and the presence of molecules that can absorb and emit light.

A team of researchers from Algoma University, Tufts University, and Wilfrid Laurier University explored the possibility of using these weak light signals to monitor brain activity. Unlike existing methods such as MRI or infrared spectroscopy, measuring ultra-weak photon emission (UPE) does not require exposure to the brain.

The experiment involved 20 healthy adults. In a dark room, photomultipliers were used to record light signals in the occipital and temporal regions of the head, and the electrical activity of the brain was measured using electroencephalography (EEG). The participants performed simple tasks – they sat with their eyes open and closed, and listened to sound signals.

The results showed that the light emitted by the brain differed from the background in its variability and frequency composition. The signals had characteristic slow oscillations with a frequency of less than 1 Hz, especially noticeable in the occipital region.

During a change in state, for example when closing the eyes, the UPE indicators stabilized and changed, indicating a connection with internal brain processes. However, the direction of changes varied among participants.

When photon radiation was compared with electrical rhythms of the brain, a weak correlation was found. Alpha rhythms, associated with a relaxed state and intensified with closed eyes, showed a connection with UPE in the occipital region, but only in this state.

Similar connections were found in the temporal region during sound stimulation, but they were insignificant.

The authors of the study note that the work has some limitations: a small sample size, a limited number of sensors, and a wide range of wavelengths recorded make it difficult to conduct a more precise analysis.

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To improve the results, it is necessary to increase the number of sensors and use more specialized filters. This will help to better localize the radiation sources and understand which brain cells are involved in the process.

There are also plans to study how these light signals manifest in other tissues of the body and how they are affected by age, gender and health status. Machine learning capabilities and new imaging techniques may help decipher UPE patterns and use them to diagnose and monitor brain diseases.

The researchers believe that photoencephalography, based on measuring ultra-weak photon radiation, could become a new non-invasive tool for studying the brain with high temporal resolution.

It will allow tracking metabolic processes associated with oxidative stress and potentially find application in clinical practice.