• Question: Why do people with Alzheimer's seem to revert back to childhood experiences/memories?

    Asked by tyrrellt to Michael, Masud, Katherine, Daniel, Catriona, Anna on 11 Apr 2015.
    • Photo: Catriona Morrison

      Catriona Morrison answered on 11 Apr 2015:

      Well I would call this the “first in, last out” phenomenon: the first memories in are the ones that remain when others have been erased or are unavailable. My research has shown that the earliest things we learn are the most robust throughout life and the easiest to bring to memory.
      Not just in Alzheimer’s Disease, but for all of us if we’re asked about memory, then what we typically recall will be memories from our childhood/teenage years/very early adulthood – this period is very special in our lives, it marks the time when we are forming a true sense of self. We’re working out who we are, our place in the world. There are seismic life events happening then, too.

    • Photo: Masud Husain

      Masud Husain answered on 11 Apr 2015:

      I’d broadly agree with Catriona’s response.

      In addition, it’s worth noting that people with Alzheimer’s disease encounter great difficulty in laying down and consolidating new events into memory. So even if recent events are often very vivid to healthy people, they’re very fragile and hard to recover for Alzheimer patients.

      In the competition for which memories might enter our awareness, older ones – which have been ‘replayed’ and inspected many times over – are always going to be at an advantage. This would be particularly the case if such memories define who we are and how we’ve got to where we are – our ‘self’.

    • Photo: Michael Thomas

      Michael Thomas answered on 13 Apr 2015:

      Some of the neuroscience research in this area studies neural networks, and how memories are stored by changing the strengths of the connections between neurons. There are two reasons why early memories appear more robust. First, the brain is more plastic early in development, meaning the connections between neurons can be strengthened more following some experience. Stronger connections will be more robust to a decline in the efficiency of neural processing. Second, we tend to think in terms of ‘distributed’ processing: knowledge or memories are spread on top of each other over the same neural networks, rather than being stored in separate locations. This means that later acquired memories are in some sense stored ‘on top of’ earlier acquired memories. The kind of damage produced by Alzheimer’s removes the top layer, meaning the layers underneath are more readily recalled.

Comments

  • Photo: specialsymbol

    specialsymbol commented on :

    Thank you, Michael Thomas.

    Now that brings up an interesting point: Neural networks.

    As far as I understood learning, neural networks are set up by creating / reinforcing links between neurons. Is this correct?

    The logical next question then would be: does accessing that link automatically lead to further reinforcement? That is, either by seeing / reading anything that affects that connection (read: learning) or by accessing it directly (read: recalling)? If this happens, is it exclusive to one of those processes or do both have the same effect?