In the belly, babies see more than you think

The retina has a more important role than expected in the fetus. Indeed, photosensitive cells present in this part of the eye would have a role to play during pregnancy, and well before the baby can see. They allow the blood supply to the retina, the establishment of the circadian rhythm and the reflex of the eye to light. A study, published in the journal Current Biologygoes in this direction.

Cells that communicate in a network…

The light-sensitive cells found in the retina make up a thin sheet of brain tissue located at the back of the eye. Initially, they were thought to be simple “on-off” switches, allowing the “day system” to be installed. But researchers at the University of California, Berkeley (USA), have discovered that these cells communicate within a network, which gives the retina greater sensitivity to light. This light can, moreover, influence the behavior and the development of the brain in an unsuspected way. In the developing eye, 3% of cells are sensitive to light. The researchers discovered six cell subtypes that communicate with various places in the brain. Some speak, for example, with the suprachiasmatic nucleus to regulate our internal clock, our day-night cycle.

… And which have an influence on emotions

However, some cells communicate with more surprising places, such as the amygdala, which processes emotions. “Given the variety of these ganglion cells and their projection to many different parts of the brain, I wonder if they play a role in how the retina connects to the brain,” asks Marla Feller, professor of molecular biology and lead author of the study. “Maybe not for visual circuits, but for non-visual behaviors. Not only the pupillary light reflex and circadian rhythms, but also perhaps explaining issues like light-induced migraines, or why light therapy works for depression.” When conducting this study, the researchers did not expect this cellular network to work so soon. “We thought that the mouse pups and the human fetus were blind at this stage of development,” concedes Marla Feller.