Why do we tend to forget earlier memories, especially those from childhood, as we get older? New research from The Hospital for Sick Children (SickKids) brings fresh insight into the mystery of infantile amnesia and begins to explain why we have no memories from our earliest years. Researchers demonstrate that new neuron formation, or neurogenesis, in the area of the brain where memories are stored, called the hippocampus, is associated with memory loss.
The study, published in the May 9 edition of Science, found that increased neurogenesis results in more forgotten memories.
Researchers tested the memories of adult and infant mice by behavioural conditioning, a test in which the subject learns to predict events in a particular situation. In adult mice, increasing neurogenesis after memory formation promoted loss of those memories. For infant mice, high levels of neurogenesis resulted in a rapid loss of hippocampal-dependent memories. When their levels of neurogenesis were reduced infant memories were more persistent.
“As new neurons integrate into the hippocampal brain circuits they modify those circuits, and this leads to the loss of information stored in those circuits, or forgetting,” says lead author Dr. Paul Frankland, Senior Scientist in Neurosciences & Mental Health at SickKids. “This form of ‘spring cleaning’ may help to declutter the hippocampus, getting rid of unnecessary information so that new, important information can be stored.”
Frankland explains that these new findings don’t mean infantile amnesia will become a thing of the past. While researchers could increase the capacity to remember childhood events, reducing neurogenesis is associated with many cognitive problems.
This research was supported by the Canadian Institutes of Health Research and the “Chase an Idea in Paediatric Neuroscience” grant from The Centre for Brain & Behaviour at SickKids.
Text by Rebecca Milec, SickKids Hospital
Original Research Article: Akers KG, Martinez-Canabal A, Restivo L, Yiu AP, De Cristofaro A, Hsiang HL, Wheeler AL, Guskjolen A, Niibori Y, Shoji H, Ohira K, Richards BA, Miyakawa T, Josselyn SA, Frankland PW. Hippocampal neurogenesis regulates forgetting during adulthood and infancy. Science. 2014 May 9;344(6184):598-602. doi: 10.1126/science.1248903.
http://www.sciencemag.org/content/344/6184/598.long