Mammals dream about the world they are about to experience before they are born

As a newborn mammal opens its eyes for the first time, it can already make visual sense of the world around it. A new Yale study suggests that, in a sense, mammals dream about the world they are about to experience before they are even born. Writing in the July 23 issue of Science, a team led by Michael Crair, the William Ziegler III Professor of Neuroscience and professor of ophthalmology and visual science, describes waves of activity that emanate from the neonatal retina in mice before their eyes ever open. "At eye opening, mammals are capable of pretty sophisticated behavior," said Crair, senior author of the study, who is also vice provost for research at Yale." But how do the circuits form that allow us to perceive motion and navigate the world? It turns out we are born capable of many of these behaviors, at least in rudimentary form. Imaging the brains of mice soon after birth but before their eyes opened, the Yale team found that these retinal waves flow in a pattern that mimics the activity that would occur if the animal were moving forward through the environment. Going further, the Yale team also investigated the cells and circuits responsible for propagating the retinal waves that mimic forward motion in neonatal mice. Human babies are also able to immediately detect objects and identify motion, such as a finger moving across their field of vision, suggesting that their visual system was also primed before birth.