Scientists have discovered that while the developing foetus can not see images, they can detect light by the second trimester.
The eye connects other functions
A new study by the University of California has discovered that foetal eyes work differently than once thought and that the retina may play a part in brain and behavioural development.
The retina is a layer at the back of the eyeball that contains cells which are sensitive to light. The cells trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed. – source: Lexico
It was originally thought that the cells in an in-utero baby’s growing retina helped them to develop their body clock aka circadian rhythm.
But now researchers have worked out that these light-sensitive retina cells have a lot more going on than that. (As impressive as that is!)
They’ve just published their findings in the journal Current Biology.
The research team found that the retina’s cells — called ganglion cells — are part of a network that makes the retina more light-sensitive than originally thought.
And not only are the cells more sensitive to light than once assumed, but they’re also using this interconnected network to talk to each other and possibly assist with other developmental functions.
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These clever cells are doing this in ways scientists had not originally imagined.
While some cells are connecting to that all-important body clock, for sure, or the centres that control pupil dilation and constriction, others are doing freshly-discovered stuff.
Some foetal retina cells have been found to connect to the perihabenula, which regulates mood.
Others connect to the amygdala, which processes emotions.
“A surprising thing”
Marla Feller is a UC Berkeley professor of molecular and cell biology and was senior author of the paper about these findings.
She says that this research may give us clues about how light impacts the brain, and it could provide more information about how to treat some health conditions not previously associated with this early development.
“Given the variety of these ganglion cells and that they project to many different parts of the brain, it makes me wonder whether they play a role in how the retina connects up to the brain,” she told Science Blog.
“Maybe not for visual circuits, but for non-vision behaviours. Not only the pupillary light reflex and circadian rhythms, but possibly explaining problems like light-induced migraines, or why light therapy works for depression.”
“We thought they (mouse pups and the human foetus) were blind at this point in development,” Feller said, noting they’d underestimated the eye’s development at this early stage of life.
“We thought that the ganglion cells were there in the developing eye, that they are connected to the brain, but that they were not really connected to much of the rest of the retina, at that point. Now, it turns out they are connected to each other, which was a surprising thing.”