The role of biophotons in the brain is a growing area of research in neurobiology – and where there are photons there might be quantum mechanics. Betony Adams and Francesco Petruccione explore this developing, and contentious, field of quantum biophysics

The light of the mind is blue, wrote the poet Sylvia Plath (“The Moon and the Yew Tree” 1961). But it seems it may actually be red.

That’s because recent research suggests a link between intelligence and the frequency of biophotons in animals’ brains. In 2016 Zhuo Wang and colleagues at the South-Central University for Nationalities in China studied brain slices from various animals (bullfrog, mouse, chicken, pig, monkey and human) that had been excited by glutamate, an excitatory neurotransmitter. They found that increasing intelligence was associated with a shift in the biophoton’s frequency towards the red end of the spectrum (PNAS 113 8753).

Admittedly, it is unclear what the measure of intelligence actually is, and the study has drawn criticism for its lack of an explanatory mechanism; correlation, as the mantra goes, does not mean causation. However, the role of biophotons – spontaneous ultra-weak near-ultraviolet to near-infrared photons in biological systems – is a growing field of research in neurobiology.

Light has such symbolic resonance for humanity. It features in art, religion, literature and even in how we talk about knowledge – we speak of “enlightenment” and “seeing the light”, for example. It seems fitting, therefore, that it might play a physiological role as well. Just how light is involved in the signalling processes that constitute the central nervous system and its emergent property, consciousness, is still not clear. But inevitably, where there are photons, there might be quantum mechanics.

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