Childhood Memories Are Erased By Growth of New Neurons

By Carl Engelking | May 9, 2014 1:44 pm

Newly generated neurons (white) integrating into the hippocampus. Credit: Jason Snyder

For most of us, early childhood memories resemble videos posted on Vine: brief, random snippets of various times, places and people. But our difficulty recalling our earliest life moments isn’t a result of diminishing brainpower; quite the contrary, it could be the byproduct of our brains’ processes of self-renewal.

In a study published this week in the journal Science, researchers show that our brains’ continual process of adding new neurons disrupts older memories, making them increasingly foggier or non-existent. Since neural regeneration peaks when we are babies and slows down as we age, this finding might explain why we don’t recall memories from our infancy.

Forgetting the Past

Both humans and mice experience what’s called “infantile amnesia,” or forgetting things from the time we were babies, so mice made ideal test subjects.

Researchers conditioned adult mice to fear an environment in which they received repeated shocks. They then gave some of those mice access to running wheels, since running has been shown to naturally boost levels of neuron birth, or neurogenesis. When, six weeks later, researchers returned the mice to the environment that they had been trained to fear, they discovered that the exercising mice had added more neurons and had largely forgotten their fear; the sedentary mice, on the other hand, were still traumatized.

As another test, researchers gave a group of infant mice drugs to slow their neurogenesis—which is high early in life—and again conditioned them to fear a particular enclosure. When tested a week later, the brain-growth-stunted group were twice as likely to remember their fear as were their untreated littermates.

Moving Forward

Making new neurons is crucial to the learning and memory, both in infancy and throughout our lives. These results complicate that picture, however, making neuron birth a trade-off of learning new things while forgetting older ones. Our brains, suggest the authors of a related commentary, are like “palimpsests from the middle ages—manuscripts written on top of older washed-off texts.” Something to think on next time you curse your unreliable memory.

CATEGORIZED UNDER: Mind & Brain, top posts
  • emma852

    My Uncle Harrison recently got Infiniti Q50
    Sedan from only workin part time on a home computer… go to this website C­a­s­h­D­u­t­i­e­s­.­ℂ­o­m

    • paenus


  • guest

    If only spammers’ neurons would regenerate to the extent that they would forget how to spam…

  • Longmire

    Its not hard to conclude that every new thing we learn something else is forgotten. Perhaps that is why Americans get such a bad rap for not being very smart, not because they aren’t but because they never really build long term memories (knowledge) but have been conditioned to constantly rebuild their brain to adapt to the overstimulation of their environment.

    • eirikr1

      But the brain also attaches an “importance level” to memories. An anatomy/physiology student is going to remember which DNA base pairs are purines for the upcoming test. What the student had for breakfast on a certain day two weeks ago is another matter. And so is the name of a childhood friend when they were only four years old.

      I suggest that short term unimportant memories are marked as disposable space, and all of the infancy memories are similarly marked.

    • eirikr1

      Off the subj, but “Americans get such a bad rap for not being very smart,” because we (supposedly) get low grades in Math.
      We do not, however, get credit for taking two math systems; one being the easy sys everyone else that we’re compared to is taking..and the other..advanced carpenter / engineering math that only commonwealth nations fool with.
      We deserve extra credit, weighted grades, or at least deserve to grade ourselves on a curve….

    • jaia

      While new memories can interfere with long ones, learning more things and making connections between them actually strengthens your memory.

    • pozzo0

      you are certainly an optimist and creative!

  • bucys1

    so what we are saying here is that exercise leads to memory loss

    • eirikr1

      well, no…but that’s as good an excuse as any for why I don’t exercise like I should.

  • Jane Beckman

    Are they sure they are not just archived? I note that certain stimulus (most notably scents) can bring back very early childhood memories. And some days, it’s easier to recall something that happened at age 2 than it is to remember something from, say, 5 years ago.

  • Mia Dodson

    Please sign me up as a test subject

  • Allen Howell

    How does this explain elderly people with Alzheimers forgetting recent events and people, but can more easily recollect memories of long past events. Some immigrants with Alzheimers have been reported to lapse back into childhood languages they haven’t spoken since they were toddlers.


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