Long term memories and associations.

Think back to the year 1969. Can you remember a specific event that happened in that year?

Yes? Or maybe no?

What if I then said, think of “Stardust”?

Or Jimi Hendrix?

Now what does that bring to mind?

1969 was the year of the Woodstock festival when 500,000 fans descended on a field in New York State to listen to three days of music.

It was also the year Richard Nixon was sworn into office and the year that Neil Armstrong took “One small step for man, one giant leap for mankind”

Memories are like layered dressing. When recalling a memory from a while back we look for the associations of where we were, what we may have been doing, who we were with. For me I have visual images of Hippies wearing headbands and large peace symbol necklaces, the Vietnam War, the smell of marijuana and incense.

Last Saturday I went to a commemorative concert that featured some of the music from the Woodstock concert. As soon as the music started, song after song was so familiar, I found myself tapping my feet and singing along to all of the words, which miraculously were still there as well. I was reliving memories of songs and names of bands I hadn’t thought about for nearly four decades.

Our long-term memory has the remarkable capacity to help us recall these events and when primed, all the associations come tumbling in.

How does our remarkable brain keep this seemingly forgotten information ready at our fingertips?

Our memory is not static. In fact our memories of events that we replay are embellished and altered over the years. It is thought that a memory does not become more stable until it is at least 10 years old. Plus each time we recall these older memories back into our conscious thinking, they become unstable again. With each recall that memory is more at risk of interference from other memories and events, which can get intertwined with the original story.

Maybe that’s why the story of “the fish that got away” gets bigger and bigger with each telling. It’s our memory changing the story. We really do believe those changes though. Maybe that’s why also when my husband is telling the story of an adventure we both experienced on a particular holiday, his recall can be so different from my recollection of those particular events.

Far from being stored in one particular place like a filing cabinet, the different components of our memories are shared around the cortex or surface of our brain. Memories that are associated with emotion tend to be the strongest, which is why certain events such as our personal triumphs or tragedies remain most vivid.

So what happens to those memories that don’t serve us anymore? If they are never recalled, then the brain’s clever synaptic pruning takes place. Dendrites disappear and those inter-neural or brain cell connections are lost. The beauty of this is that this then frees up space for new connections and new memories to form. A form of sustainable memory farming perhaps?

Trying to lose a strongly emotionally charged memory whether it is positive or negative, is hard work, as our brain has to rewire itself to produce a new robust circuit stronger than the pre-existing one. Our brain cells are in constant competition and it will always be the strongest circuit that wins.

Rehearsal and repetition is the key to introducing new ideas for long-term memory. This is vital for us for example when learning how to use new technology or learning facts needed to pass an exam or test. Sleep is also needed to help embed new learning. Studies have shown that after being given new information, ideally we need around 8 hours sleep to really consolidate the new ideas and process it to make it available for long-term recall.

In Alzheimer's disease, more recent memories are lost first. The older memories stay relatively intact. My mother-in-law had Alzheimer's. She had lots and lots of stories she loved to tell us. We heard them many, many times. Mostly they related to her experiences of living overseas, of World War Two and of her childhood growing up on the Isle of Wight in England. As her disease progressed her memories of these previous events started to disappear. What we noticed also was that as her memories disappeared they did so in reverse chronological order. We tried to keep her in the present, talking to her about current events, her grandchildren and having general discussions. But whenever she spoke she would immediately revert back to an old favourite story, completely unrelated to the here and now. Her brain simply couldn't process new information. Gradually the stories from the seventies and eighties disappeared, then the stories about her time working for the S.O.E in the forties until she only had one story left about a time she went swimming in the sea as a child with her pet dog.

Our memories are fragile. But with ongoing mental stimulation, being involved in different mental activities to stretch our mind, being physically active and looking after our general health with good nutrition and keeping stress under control. There is much we can so to keep those memories alive and to continue to enjoy our lives with our mental faculties fully intact.

Meanwhile I am still happily enjoying the recent rewind in my mind of those classics from Canned Heat, the Band and Crosby, Stills, Nash and Young.

Yeah baby, let’s dig it.