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Orexin influences pupil size

The way the brain regulates pupil size is different from previously thought: fundamentally responsible is the neurotransmitter orexin, as researchers at ETH Zurich have now shown. This discovery could well alter our understanding of consciousness and illnesses such as narcolepsy and Alzheimer’s.

Not only light changes the size of the pupil, mental strain and emotional impressions also have an influence on it (symbol image). (Photograph: Adobe Stock / Montage)

In brief

  • When the orexin neurons in the brain are stimulated, pupils expand, new research in mice shows.
  • Orexin is central to the regulation of pupil size. When the orexin system is switched off, the pupils remain constricted.
  • In future, scientists would like to use pupil size to measure the activity of orexin neurons.

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