Human memories are very complex and are stored in many different parts of the brain, so memory retrieval will face many challenges.
If there were a full model of the human brain, scientists could theoretically determine the location of the memory they want to recover. Image: of Aeon
When people die, they often leave behind personal items, but what happens to their entire life experience? Can scientists retrieve and restore memories from their brains? According to Don Arnold, a neuroscientist at the University of Southern California, recovering partial memories may be possible, but there will be many technical challenges.
With today’s technology, memory retrieval can happen as follows: First, identify the group of brain cells, or neurons, that encoded a specific memory in the brain and understand how they connect. Then, activate those neurons to create an artificial neural network – a machine learning algorithm that simulates how the brain works – that approximates it.
Memories are encoded by groups of neurons, Arnold said. Short-term and long-term memories form in the hippocampus. Other parts of the brain store different aspects of a memory, such as emotions or other sensory details, according to the Cleveland Clinic. Groups of neurons associated with a single memory leave a physical trace in the brain called an engram.
Neuroscientists have identified engrams in the hippocampus of rat brains. For example, in a 2012 study in the journal Naturethe authors discovered certain brain cells associated with memories of a fear-inducing experience.
If in the future, scientists have a full model of the human brain, they could theoretically pinpoint the location of the memory they want to recover, Arnold said. But memories can be complex, especially long-term memories tied to places, relationships, or skills. Recovering the memories of the deceased is further complicated because aspects of a memory are scattered throughout the brain. For example, sensory details may be stored in the parietal lobe and sensory cortex.
Neurons in engrams are connected through synapses – spaces between neurons through which electrochemical signals pass, according to the US National Library of Medicine. When activated, memories trigger a chain of synapses between these groups, which can be stored in many different brain regions.
Initially, neurons active during the original event will create an engram. But over time, there is evidence that memories move to other locations as they consolidate in the brain, Arnold said.
Cutting out the cells that make up engrams is not a good way to get memories. Engrams are not really memories but just storage. Therefore, even if an engram is found, it is difficult to recreate the original event as the memory owner experienced it.
“Memory is very reconstructive, meaning you remember pieces of an event, but you don’t really grasp the whole thing,” said Charan Ranganath, director of the Memory and Resilience program at the University of California. , Davis, shared.
It’s an efficient way to create memories, because the brain can use what it already knows to fill in the gaps on its own and doesn’t have to create a new “memory” for every part of the experience. For example, a person may remember eating chocolate cake and playing tag at their 5th birthday party. They don’t remember other details like who attended or whether it was raining. However, they retain the overall memory of the experience.
The best artificial neural network model would entail scanning the brain of a person repeatedly recalling events throughout their life, according to Ranganath. Then perhaps an expert could use a neural network to recreate a specific memory when the person passes away. However, this situation occurs when it is assumed that memories are static, like a file on a hard drive replaying a sequence of events. Instead, memories are dynamic.
“We attach all sorts of meanings and perspectives to our memories in ways that don’t necessarily reflect the true events. We don’t ‘replay’ the past but just imagine what the past might have been like,” Ranganath said. According to him, all of this is aimed at understanding past experiences as more than simply a series of events. So, at least for now, the memory of a life dies with the person who lived it.