Have you ever wondered why your loved one with dementia can remember something that happened to them decades ago in great detail but forgets what you said just moments ago? This is the difference between long term and short term memory loss and it is often seen in people who have dementia or Alzheimer’s.


Every single day your brain processes thousands of thoughts and experiences, some you will only recall for a matter of seconds or minutes, others your brain will file away for a number of days. Some memories will be ingrained for decades, or perhaps never leave you. This forms the basis of memory, and memories can be divided into short term or long term.


Short term memory

It is also called ‘primary’ or ‘active’ memory and refers to memories stored anything between 30 seconds to several days. These memories do not hang around very long, either they are not that important or they form part of your habitual day to day routine that does not need recording. Effectively they are booted from your brain to make space for new memories. Imagine how cluttered and full our minds would be if we tried to recall from a brain that remembered every minute fact or experience all the way from early childhood.


However, if you make a point of remembering a fact then this memory is transferred to the part of your brain where your long term memories are stored – the frontal lobe.


Long term memory

This brings us to long term memory; it is generally referred to when we recall things that have happened or thoughts we have had weeks, months or years ago. Without you even knowing it, your brain is filtering all your thoughts and experiences into two boxes – short term or long term. The times when you are more conscious about it, such as when learning a speech or phone number off by heart, your brain makes physical connections between its cells to retain that memory.


What your brain decides to retain as long term memory is not always consistent, sometimes traumatic experiences are hardest to forget and yet you would never consciously try to remember them. Memories with strong emotional connections often linger the longest, such as treasured moments with loved ones or exhilarating experiences as a child. Sometimes even a smell can elicit a powerful memory or emotion, simply because of the strong sensory experience when the memory was created.


How does this work if you have dementia or Alzheimer’s?

Back to the question of why your loved one can remember their childhood dog’s name but not what they ate for lunch that day; it is the way the disease affects the brain. Dementia or Alzheimer’s causes changes in the brain that affect the short term memory first. Long term memories will at some point be affected by the condition, but not for a while.  

Short term memory loss is one of the first signs of dementia, and the symptoms are progressive – which means they start slowly and gradually get worse. If your loved one is experiencing some memory difficulties or a decline in their mental abilities be sure to see a specialist as it is important to get an accurate diagnosis for dementia related symptoms.