For most of the 20th century, neuroscience treated our memories like inert packets of information. They were created through Pavlovian reinforcement, and then just shelved away in the brain, like dusty old books in a library. While this approach led to many important discoveries, like CREB, Cam Kinase and cAMP, it also created a strange blind spot in the literature: while scientists were starting to understand how we create a memory, then had no idea how we remember our memories. What happens during he recollection process?
An important paper arrived in 2000, when Karim Nader, Glenn Shafe and Joseph LeDoux at NYU discovered that the act of remembering also leads to cellular changes in the hippocampus. This means that everytime we remember anything, the neuronal structure of the memory is delicately transformed, a process called reconsolidation. The moral of this research is rather bleak: the more you remember something, the less accurate your memory becomes.
Since that paper came out, reconsolidation has become a hot topic. Neuroscience is suddenly interested in the fictionality of memory, how the mind is constantly rewriting its past in response to the present.
Now comes news of a very cool experiment, which demonstrates that we also use our fictional past to imagine the future. Patients suffering from hippocampal lesions – this causes severe amnesia – are unable to ponder the future, precisely because they can’t recall and reconsolidate their past. (The authors focus on an eerie spatial deficit in amnesiacs.) Since they can’t alter their memories, they are permanently trapped in the present:
The new study, reported last week in The Proceedings of the National Academy of Sciences, is the first rigorous test of how brain-injured people with amnesia mentally inhabit imaginary scenes. The results suggest that to the brain, remembered experience and imagined experience are reflections from the same mirror, rich inner worlds animated by almost identical neural networks.
“The study suggests that these patients have fragments, the brick and mortar to create new scenarios, but their descriptions lack coherence because they don’t have the scaffolding the hippocampus provides,” said Morris Moscovitch, a neuroscientist at the University of Toronto, who was not involved in the study.
This paper opens up a tantalizing and very post-modern possibility: not only do we transform our memories every time we remember them, but we might also transform them whenever we conjure up the future.