Many of Earth’s critters have the ability to emit a visible glow, but humans aren’t usually considered among their number.
This may not be entirely correct. Going all the way back to 1923, a number of studies have found humans luminesce in frequencies that would be visible if they weren’t too faint for us to actually see. From the moment of conception until we shuffle off this mortal coil, we literally shine.
It’s controversial, absolutely, but it’s possible that detecting these ‘biophotons’ could tell us a thing or two about what takes place beneath our skin.
In a new study, a team of researchers led by biologist Hayley Casey of Algoma University in Canada has investigated the extremely weak glow of one lump of tissue in particular: the brain that resides inside the skull of every living human. They carefully recorded the faint glow of the human brain from outside the skull, and found that it changes according to what the brain is doing.
This, they say, offers an exciting new possibility for gauging brain health: a yet-to-be-developed technique they call photoencephalography.
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“As the first proof-of-concept demonstration that ultraweak photon emissions (UPEs) from human brains can serve as readouts to track functional states, we measured and characterized photon counts over the heads of participants while they rested or engaged in an auditory perception task,” they write in their paper.
“We demonstrated that brain-derived UPE signals can be distinguished from background photon measures. Additionally, our results suggest that for a given task, the UPE count may reach a stable value.”
Everything in the Universe with a temperature higher than absolute zero – humans included – emits a type of infrared radiation called thermal radiation. When we talk about UPEs, it is a distinct phenomenon from thermal radiation.
UPEs are emitted in near-visible to visible wavelength bands, and are the result of electrons emitting photons as they lose energy, a normal by-product of metabolism.
Casey and her colleagues sought to conclusively distinguish brain UPEs from background radiation, and determine whether these UPEs exhibit patterns consistent with different levels of brain activity.
They placed each of their study participants in a dark room. An electroencephalography (EEG) cap was placed on the participant’s head to monitor their brain activity, and photomultiplier tubes were positioned around them to record any light emissions. These are extremely sensitive vacuum tubes that can detect even the very faintest light.
Then, the participants were recorded at rest, and performing sound-based tasks (so they could do them in the dark). The results showed not just that UPEs are real and measurable even from outside the participants’ heads – there was also a clear correlation between UPE output and the activity registered by the EEG cap.
Future work, the researchers say, could delve into how neuroanatomy might impact UPE output, as well as how different activities manifest in patterns of UPEs, rather than just the two states of brain rest and brain activity.
We also don’t know if each individual has a UPE ‘fingerprint’ that would need to be recorded as a baseline against which to measure anomalous activity.
“We view the current results as a proof-of-concept demonstration that patterns of human-brain-derived UPE signals can be discriminated from background light signals in darkened settings despite very low relative signal intensity,” the researchers write.
“Future studies may find success in using select filters and amplifiers to sieve and enhance UPE signal features from healthy and diseased brains.”
The paper has been published in Current Biology.
