The new study suggests that there are two different systems that affect pupil dilation and contraction.
Doctors have long studied the pupil’s response as an indicator of the level of consciousness. However, those who have taken traditional antidepressants have probably noticed that their eyes look like saucers in response to the increased levels of serotonin in their brains. Science Alert writes that in a new study, scientists from the Swiss Federal Institute of Technology Zurich have discovered the mechanism responsible for these reactions.
According to neuroscientist Nikola Gruich, co-author of the study, the effect was so strong during the experiment that he and his colleagues immediately knew they had stumbled upon something important. Researchers now believe that the neurotransmitter orexin, also known as hypocretin, may be behind all this, influencing changes through cells called orexin neurons. These cells are known to extend deep within the human brain from a small structure called the hypothalamus that directs our body’s hormonal responses to the rest of the organ.
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Orexin neurons project throughout various regions of the brain, with particularly strong connections in areas of arousal and reward. Scientists already know that it is these connections that allow them to regulate the transition between our conscious (awake) systems and the automatic state of sleep. However, their role in shorter-term states has not been adequately studied up to this point.
In the study, Gruzic and colleagues stimulated these cells in live mice using two-photon microscopy and observed how the animals’ activity correlated with pupil size. When the scientists activated some of these neurons, the pupils of the mice dilated. The results of the study showed that some groups of these neurons affect pupil size, others affect the reward system, and others affect the reward system by activating the pupil. At the same time, pupil dilation and constriction were dose dependent.
According to neuroscientist Denis Burdakov, one of the study’s co-authors, he and his colleagues concluded that the results showed a link between the orexinergic system of neurons and the control of pupillary dilation. In fact, pupils are an indicator of how active these neurons are in the hypothalamus.
Meanwhile, it was previously believed that it was the norepinephrine system that controlled the reactions of our pupils, but a new study proves that these cells actually only model the reaction of orexin neurons.
Equally interestingly, in mice lacking orexin neurons, their pupils continued to constrict at rest, but widened when running. Researchers believe this indicates the presence of a different nervous system, which also affects the size of the pupils during arousal.
Previously Focus He wrote that scientists have figured out why people yawn: it was important to our ancestors.
Source: Focus
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