Reviving Forgotten Memories in Laboratory Mice

Researchers have demonstrated that by stimulating certain nerve cells in the brains of mice, memories from infancy do not disappear but rather become difficult to access. The magazine 'Scientist' reported on this new research, noting that like humans, mice experience a period of amnesia after losing their infant memories. However, researchers now say these memories are not completely forgotten; they can be retrieved from the memory store with difficulty. The results of this scientific research were published this month in the journal 'Current Biology'. Christina Alberini, a memory researcher at New York University and one of the contributors to this study, told 'Scientist' that the research 'showed that experiences and memories from infancy remain for a long time, even if they do not manifest themselves.' Sigmund Freud first introduced the concept of 'childhood amnesia' in the late 19th century when faced with patients who could not recall the early years of their lives. Since then, scientists have tried to understand why humans and some other mammals face such issues. It was unclear whether the cause of this problem was improper memory storage or a weakness in recalling these memories. In the new study, Paul Frankland, a psychologist working at the Hospital for Sick Children in Toronto, along with his colleagues, attempted to discover which of these two conditions operates in the brains of mice. The researchers placed the mice in a special box and administered a mild electric shock to create a specific memory in their brains. When the mice were returned to the same boxes after living in a different environment for a while, the adult mice had well-registered this experience in their minds and reacted accordingly, while the infant mice completely forgot this frightening experience and behaved normally. According to 'Scientist', researchers attempted to stimulate the neurons in the hippocampus of the mice's brains, which were activated during the fear conditioning phase, by shining a laser beam. When the infant mice were placed in the box and the laser was directed at them, their memories of the electric shock were revived, and they remained motionless. Researchers activated the memory-related neurons at various time intervals of 15, 30, and 90 days after the first electric shock to the mice. At all these stages, until the infant mice matured completely, they recalled their infant experiences and remained motionless each time they returned to that box. Patricia Bauer, a psychologist at Emory University who did not participate in this research, states that the results of this new study have similarities to previous knowledge about children. Children can sometimes recall memories from their early years after receiving cues. However, this psychologist emphasizes that memories from different stages of life in humans, unlike in mice, do not solely depend on the activity of the hippocampus but are intertwined with the individual's personal life. Scientists believe that psychology now needs to investigate which aspects of our mental functions influence the storage and classification of memories, and how and when they affect behavior.