According to a new study from Yale University, judging by the activity of the brain, baby mammals can already see themselves in the world they are about to be born into, even before their eyes open.
When a newborn mammal first opens its eyes, it can already visually perceive the world around it. But how does this happen before they have vision?
A new study from Yale University suggests that in some sense mammals dream of the world they are about to enter even before they are born.
In a recent issue of the journal Science, a team led by Michael Crair, professor of neuroscience William Ziegler III and professor of ophthalmology and visual sciences, describes waves of activity that emanate from the retinas of newborn mice even before their eyes open.
This activity disappears shortly after birth and is replaced by a more mature neural network that transmits visual stimuli to the brain, where further information is encoded and stored.
"When you open their eyes, mammals are capable of rather complex behavior."says Crair, senior author of the study, who is also Yale University's assistant vice rector for research." But how are the patterns that allow us to perceive movement and navigate the world are formed? It turns out we are born capable of many of these behaviors, at least in its infancy.".
In their study, Crair's group, led by Yale graduate students Xinxin Ge and Katie Zhang, examined the origins of these waves of activity. By taking brain scans of mice shortly after birth but before their eyes opened, the Yale University team found that these waves in the retina of the eye flow in a pattern that mimics the activity that would occur if an animal moved forward through its environment.
"This early sleep-like activity allows the mouse to anticipate what it will experience after opening its eyes and be ready to respond immediately to environmental threats."- said Crair.
Going further, the Yale University team also investigated the cells and circuits responsible for propagating waves in the retina that mimic the forward movement of newborn mice. They found that blocking the function of the stellate amacrine cells, which are cells in the retina that secrete neurotransmitters, prevents waves from propagating in a direction that mimics forward motion. This, in turn, interferes with the development of the mouse's ability to respond to visual movement after birth.
Interestingly, in the adult mouse retina, these same cells play a crucial role in a more sophisticated motion detection circuitry that allows them to respond to environmental cues.
Mice, of course, differ from humans in their ability to quickly navigate their environment shortly after birth. but human babies are also capable of immediately detecting objects and detecting movement, such as a finger moving across the field of view, suggesting that their visual system was also prepared before birth.
"These brain circuits self-organize at birth, and some of the early learning has already been done," Crair said. "It's like a dream about what you are about to see, even before you open your eyes.".