“Now if you’ll just look right here…”. A sudden flash. You blink, wig snatched, and Tommy Lee Jones fills the blank with a new story. Instead of an intergallactic crime, you’ve witnessed a gas leak or a flash of light refracted from Venus. The audience laughs, its absurd, just sci-fi gadgets. Except, there might be more truth to it than you would have expected.
Each time you recall any stored memory, your brain does something seemingly counterintuitive: it momentarily forgets it. This process of reconsolidation doesn’t delete it completely, it’s just destabilized and susceptible to interferences. To distinguish reconsolidation from extinction or regular learning, there needs to be a modification of the exiting information, not the encoding of something new. Within seconds to minutes after recall a “reconsolidation window” opens, making the memory labile and vulnerable to modification. If you miss that window, the memory stabilizes and becomes fixed again. But hit it with the right interference and you can edit what was once encoded.
The recalled memory requires new protein synthesis in the amygdala, the believed site of memory storage in fear learning, to be resaved. In their research on the reconsolidation of fear memories, Nader, Schafe and Le Doux used anisomycin, a protein synthesis inhibitor, injected into the lateral and basal amygdala of rats, immediately after memory reactivation. They played the rats the same tone originally paired with a foot shock, which should be enough to open the reconsolidation window. The result? Amnesia on all later tests. Without the reactivation, their memory stayed intact. The extent of the reconsolidation window was determined to be around 6 hours and the memory was proven to be susceptible to reconsolidation up to 14 days after conditioning. The anisomycin still produced amnesia, leading to the conclusion that even old and well-consolidated memories can become labile during recall. These findings defied the earlier prediction about memory consolidation and the formation of long terms memories. The researchers proposed to to reframe the definition of consolidation as such that would view ‘active’ rather than just ‘new’ memories as labile and requiring protein synthesis consolidation.
Although reconsolidation has been demonstrated to be universal across a wide range of species from rats to sea slugs to humans and across memory types such as fear, spatial memories, motor sequences or object recognition, some conditions may still influence the outcomes. The most rooted, powerful or emotional memories are harder to destabilize and alter. The lenght of the reactivation, sleeping or new learning also introduce some limits, yet these factors are not absolute, since we could undermine them using increased reactivation intensity or pharmacological agents for boosting neuroplasticity.
The last part of the puzzle however, is something the creators of Men In Black might actually be doing right – the flash. Even if we reactivate a memory, we still need a means to destabilize it. In the case of a memory alteration, we need to introduce a factor that feels slightly off. If everything played out perfectly as was expected, there would be no need to give the brain an update. This presentation of new, mismatched information is the ‘prediction error’, or in the case of the neuralyzer, the flash of light.
In the real world, a neuralyzer might not be able to delete an event, but there is research on how we could make it feel a different way. Trials of erasing the emotional component of arachnophobia, while maintaining the declarative memory of meeting a spider have been shown to be possible. In 2015, Soeter & Kindt showed that fear could be less aversive by rewriting the emotional tone. This theory has been applied to standard extinction therapies, where working within the reconsolidation window could permanently alter original memories instead of creating a competing one. While we may never precisely replicate a silver pen that can wipe ones mind, we are gradually learning what it means to create memories and how to shape them to our needs.
