Despite advances in understanding how memories are formed and stored, the retrieval of memories after death remains an elusive and complex challenge.
Memory formation is one of the most intricate processes in the human brain. Human memories have a complex structure, especially long-term memories that may be tied to locations, relationships, or skills. The complexity arises because memories are not stored in a single location but are distributed across regions of the brain.
Neuroscience research suggests that human memory is reconstructive, meaning that individuals remember bits and pieces of an event but do not capture the whole experience. These memories are influenced by emotions and perspective, making the retrieval of complete and accurate memories even more challenging.
The concept of the engram refers to the physical trace left in the brain by groups of neurons associated with a single memory. The engram is created when an event is encoded by neurons in the hippocampus, a key area for memory formation, reports Live Science. However, engrams represent the physical structure of memories, not the memories themselves.
Neuroscientists and neurobiologists have identified engrams in the hippocampi of mouse brains, including specific brain cells associated with a memory of fear. This was revealed in a 2012 study published in Nature. These findings in animals have provided valuable insights but show the limitations when translating this knowledge to humans.
Identifying memory traces in humans is much more difficult than in animals due to the complexity of the human brain, reports SciencePost. Human memories are often multiple and intertwined, integrating not only facts but also emotions, relationships, and specific contexts. The intertwining makes it exceedingly difficult to pinpoint and extract individual memories.
"The human brain does not store all the details of a memory in a single area," notes SciencePost. For instance, sensory details can be stored in the parietal lobe and sensory cortex, while emotions related to an event may be recorded in the limbic system. Memories associated with emotions or sensory details are thus spread across multiple brain regions.
Retrieving the memories of a deceased person is more complicated because the discrete parts of a memory are dispersed in the brain, making recovery challenging. The dynamic nature makes it difficult to reconstruct accurate memories after death, reports Live Science. The degradation of the brain after death further complicates any attempts at retrieval, as neurons and synapses deteriorate rapidly, making preservation impossible.
"You get this sort of cascade of neurons that encode these different things, and each one of them is connected in this engram," said Don Arnold, a neuroscientist at the University of Southern California, in an interview with Live Science. He explained that engrams represent the physical structure of memories, but they are not the memories themselves, making retrieval extremely complex.
Even with advances in technology, creating a machine learning model to retrieve memories from a deceased person's brain remains far off. Even if an engram is found, it would be difficult to recreate the original event as experienced by the deceased person. Memories are not perfect recordings of past events but are influenced by emotions and perspectives, adding layers of complexity to any potential retrieval process, reports Live Science.
"Human memory is not just a static recording of events; it is a dynamic process involving the retrieval of pieces of information and filling in the gaps with interpretation," said Charan Ranganath, a neuroscientist, according to SciencePost. He further emphasized that "we imbue our memories with all sorts of meaning and perspective in a way that is not necessarily reflective of the event."
As noted by Live Science, the memories of a life lived will remain sealed within the person who experienced them, and once that person is gone, those fragments of the past will likely vanish with them. The only way to preserve a loved one's memories is through the stories, photographs, and legacies they leave behind.
This article was written in collaboration with generative AI company Alchemiq