“What matters in life is not what happens to you but what you remember and how you remember it.” – Gabriel García Márquez
Every day experiences accumulate to make up the memories that define who we are and what we call our lives. We live, we remember, we make meaning.
Generally we think remembering is good, and of course, forgetting is at the core of the devastation wrought by Alzheimer’s Disease. But remembering can be trouble, too. Traumatic memories can hijack normal mental functioning. Memories that trigger anxiety can be profoundly debilitating and sit at the core of a variety of anxiety disorders, mood disorders and post traumatic stress disorder.
This is an image of two sensory neurons from the marine snail Aplysia with synaptic contacts on the same motor neuron. The motor neuron has been injected with a fluorescent molecule that blocks the activity of a specific Protein Kinase M molecule. (Credit: Schacher Lab/Columbia University Medical Center from the CUMC Newsroom)
So is there a case to be made for changing or “erasing” such memories? How would that work, and what are the ethical implications? Aided by the marine snail Aplysia, neuroscientist Sam Schacher PhD and colleagues at Columbia University along with colleagues at McGill University have recently demonstrated that, in fact, certain memories can be selectively erased.
Dr. Schacher helps us understand a few things about memory making and erasing:
Oops, bad connection. Researchers distinguish between associative and non-associative memories. Non-associative memories are the ones that are problematic when it comes to anxiety and trauma. They are memories that get tangled up in the traumatic experience even though they don’t have anything to do with the trauma and do not serve an adaptive function. It would be like if you saw a mailbox before walking through a dark ally where you got mugged, and then every time you see a mailbox you get anxious and re-experience aspects of the trauma.
Memories – past or present? We think our memories are anchored in the past, but long-term memories are not as set in stone as our brains might have us think. Every time we revisit a memory, that memory becomes somewhat malleable again, and can be re-set in a different way – like metal being melted down and re-formed. This process is known as reconsolidation, and it explains why our memories can change slightly over time. This is what makes it possible for people to “rewrite” history – making memories actually more an amalgam of past and present.
It all goes back to Darwin. Some memories that get associated with trauma are adaptive. In the example of the alley mugging, the traumatic memory of being in a dark alley is helpful because it will help us remember to avoid similar dangerous situations in the future. The non-adaptive associations, the mailbox kind, are the ones that clinicians try to extinguish with psychotherapy.
Fast forward to humans and mental health. Dr Schacher and colleagues suggest that – at least in snail neurons – non-associative memories can be isolated in the brain for re-programming without altering associative memories because a different kind of molecule regulates non-associative versus associative memories. Extrapolating from snails and mice, scientists are exploring whether targeted biological interventions might augment psychotherapy one day to help rid people of traumatic memory associations that cause anxiety and impair functioning without touching the necessary adaptive memories.
Wait a Minute! Didn’t we say our memories make up who we are? Don’t we have lots of non-associative memories that we relish – like the all over good feeling of remembering a loved one when we see or smell something that reminds us of them? Maybe such non-associative memories are not necessary for survival, but aren’t they necessary in other ways? Dr. Schacher and colleagues suspect that positive valence non-associative memories may be controlled by different molecules than negative ones. But they’ll have to do more research to know for sure.
As we are increase our understanding of how the brain remembers and forgets, the potential for new therapies is thrilling. At the same time, it is hard enough to live with the ways that people naturally and already “re-write” history. What will it mean to us – individually and collectively – if this can be done with the precision of neural manipulation? And who gets to decide?