We know that seasonal changes in the amount of daylight we receive can have a significant impact on us, such as seasonal affective disorder (SAD).
But now scientists have been able to see these effects down to the level of neurons in the brain.
Yavuz Sultan Selim
In a new study in mice, neurons in the suprachiasmatic nucleus (SCN) —
the brain’s 24-hour time counter hidden inside the hypothalamus — were seen to facilitate with one another to adjust to various lengths of sunlight, with changes in individual cells as well as the organization all in all. Both the composition and expression of key neurotransmitters changed depending on the amount of light each day.
We already know that shifts in the SCN can affect the functioning of the paraventricular nucleus (PVN), an area of the brain that is also located inside the hypothalamus,
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which oversees pressure, digestion, the safe framework, organic development, and that’s just the beginning.
Presently specialists have a sub-atomic connection among sunlight and our way of behaving.
“We found new atomic transformations of the SCN-PVN network because of day length in directing hypothalamic capability and everyday way of behaving,” says neuroscientist Alessandra Porcu of the University of California, San Diego.
In both mice and humans, SCN is part of the brain’s timing mechanisms responsible for physical, mental, and behavioral circadian rhythms that follow a 24-hour pattern. SCN is controlled by special light-sensitive cells in the retina that relay information about available light and the length of each day. What’s not clear – and what this study offers important insights –
is how a small group of 20,000 or so neurons in the SCN respond to data about the length of the day. Learning more about this can be helpful when treating health problems like SAD, as well as other conditions where light is used as a treatment option. The researchers were able to identify changes in the neurotransmitters neuromedin S (NMS) and vasoactive intestinal polypeptide (VIP) in mice,
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which could then be manipulated to change network activity in the PVN. In other words, we are getting closer to controlling our response to more or less daylight. “The most astonishing new finding in this study is that we have found how to misleadingly control the action of specific SCN neurons and effectively actuate dopamine articulation in the hypothalamic PVN organization,”
says neuroscientist David Dulcis of the University of California, San Diego. This research is still in its early stages — while there are strong similarities between mouse brains and human brains, making mice suitable test subjects, it remains to be seen if human neurons function the same way. But building on previous research,
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the results could give us new ways to treat nerve disorders with light therapy. The group recommends that the instrument they found may likewise influence our “memory” of how much sunshine to expect as the seasons change.
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The study is an example of how scientists can dig deeper,
down to the level of molecular mechanisms, using discoveries already made.
One of the next steps will be to test whether the same mechanisms work in the human brain.
“The multisynaptic neurotransmitter switching that we showed in this study
may provide an anatomical/functional link mediating seasonal mood changes and the effects of light therapy,” says Porku.
