However, remarkably, the younger rats, which had apparently forgotten the initial experience, subsequently showed they actually had kept a trace of the memory. In contrast, the rats exposed to the shock compartment at 24 days of life learned and retained the memory for a long time and avoided this place-revealing a memory similar to that of adult rats. The authors found infantile amnesia for the 17 day-old rats, which showed avoidance of the “shock” compartment right after the experience, but lost this memory very rapidly: a day later these rats quickly returned to this compartment. The first set of results was not surprising. If the rat entered the shock compartment, it received a mild foot shock. After 10 seconds, the door separating the compartments was automatically opened, allowing the rat access to the shock compartment. During the experiment, each rat was placed in the safe compartment with its head facing away from the door. To do so, rodents were placed in a box divided into two compartments: a “safe” compartment and a “shock” compartment. Adult rats, like humans, remember unpleasant or painful experiences that they had in specific places, and then avoid returning to them. The episodic memory tested in the rodents was the memory of an aversive experience: a mild foot shock received upon entering in a new place. In addressing this matter, Alberini and her colleagues compared rats’ infantile memory with that when they reached 24 days old-that is, when they are capable of forming and retaining long-term memories and at an age that roughly corresponds to humans at six to nine years old. The phenomenon, referred as to “infantile or childhood amnesia,” is in fact the inability of adults to retrieve episodic memories that took place during the first two to four years of life. This is the equivalent of humans under the age of three and when memories of who, what, when, and where-known as episodic memories-are rapidly forgotten.

In their study, which appears in the journal Nature Neuroscience, the researchers examined the mechanisms of infantile memory in rats-i.e., memories created 17 days after birth. Sinai and Robert Blitzer, a professor at the Icahn School of Medicine at Mt. Sinai, included: Alessio Travaglia, a post-doctoral researcher at NYU Reto Bisaz, an NYU research scientist at the time of the study Eric Sweet, a post-doctoral fellow at the Icahn School of Medicine at Mt. The other authors of the study, conducted in collaboration with the Icahn School of Medicine at Mt. “Without this, the neurological system runs the risk of not properly developing learning and memory functions.”

“What our findings tell us is that children’s brains need to get enough and healthy activation even before they enter pre-school,” explains Cristina Alberini, a professor in NYU’s Center for Neural Science, who led the study. The research, conducted by scientists at New York University’s Center for Neural Science, reveals the significance of learning experiences over the first two to four years of human life this is when memories are believed to be quickly forgotten-a phenomenon known as infantile amnesia. A new study on infantile memory formation in rats points to the importance of critical periods in early-life learning on functional development of the brain.

Infantile amnesia