Fashion is for products that boost memory. But there are people who would pay dearly to forget a painful memory. As in the movie "Eternal Sunshine Of The Spotless Mind where Jim Carrey is clear from his brain the memory of his unrequited love for Kate Winslet. Science fiction? Yes, probably for humanoids. But if you feel the soul of a laboratory rat, it could perhaps be envisaged. Early recipe for sorcerer's apprentice ... Where to lodge our memories?
First problem: locate memories in your brain is not obvious. In the early twentieth century, the American psychologist Karl Lashley tried the experiment with rats that had learned to get around in a maze. The results made him puzzled: no matter where they inflicted brain injury, the poor beasts were always able to remember the way learned, as if their memories were not in a particular area of the brain but scattered throughout the cortex. It was going wrong ...
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Canadian researchers have recently discovered for example, that certain classes of neurons in the amygdala ("those who express a high level of transcription factor CREB" That whatever means) are specifically associated with good memories accurate. After conditioning the mice to fear a particular sound, they observed that the elimination of these neurons suppressed the very specific Remember the fear in these mice. Amnesia induced in mice appears to be both durable and clearly limited to that specific memory.
reconsolidation, I tell you!
For potted who can not distinguish these famous neurons in your amygdala, I can offer you another recipe. In 1999, a young American post-doc, Karim Nader proposed to his lab chief experience a bit inflated . We knew at the time that could prevent storage of an event in their rats injecting a substance called anisomycin immediately after they experienced the event in question. Despite the incredulity of the rest of the laboratory he tried a variation rather inflated: he injected anisomycin not just after the event, but when the rats were again in front of the stimulus, as he recalls the event . Bingo! The rats had become amnesic!
I feel perplexed. In what remémorisation event she could erase her memory? Has anyone ever deleted a web site just by searching on Google? Hitherto it was thought that memories consistent with neural connections in our brains quite stable and that "recall an event" was simply to turn this connection, that the revival strengthened systematically. The theory of "reconsolidation" Nader havoc with this design: according to her, mentally evoke a past event remake every time a new memory in the same way that one has memorized the event for the first time. This theory therefore predicts that if a mechanism prevents the formation a memory, the same mechanism must be able to erase the same way a memory when it tries to remémoriser. Nader's experience confirms this theory nicely. What one remembers is not the original version of the memory but that of his last evocation. Every time one remembers a memory we shall alter the content: the only intact memories are those that have been forgotten and the only way to preserve a memory is never to mention ...
The Miracles of a protein with an unpronounceable name
Let me tell you that things are not so simple. A similar experiment recently highlighted the role of a molecule (the sweet name of αCaMKII) that plays only on remémorisation but not on early learning. This time, in addition to a fear of classical learning, it also taught the rats to recognize a small place. Through a chemical machinery which I'll spare you the details, researchers can overexpress or otherwise inhibit the presence of this molecule during learning and during the memorial remémorisation:
| During learning | Just before remémorisation | Result | |
| Protocol 1 | αCaMKII overexpressed | αCaMKII overexpressed | Amnesia |
| Protocol 2 | αCaMKII overexpressed | No αCaMKII | Remembrance |
| Protocol 3 | No αCaMKII | αCaMKII overexpressed | Amnesia |
protein alpha-foo has no evident effect on learning and memory storage, however it blocks remémorisation memory. Unlike Nader's thesis, the mechanisms of remémorisation do not seem exactly the same as learning ... The fact is that the amnesic effect of alfa-trick is impressive because walking even a month after the initial conditioning. Moreover in the absence of the famous protein, rats remained perfectly capable of remembering other packaging they had learned elsewhere.
question remained whether it is the memory that is erased or only access to memory. They put the amnesic rats protocol 3 A third time in re-remémorisation situation, but this time by inhibiting the alpha-CaMKII. The rats remained amnesic, proof that it was the memory itself had disappeared.
Post-traumatic stress
And then to humans? It exists in the United States a molecule (propanolol) known to treat hypertension and plays a role similar to the amygdala brain that substances just mentioned. Besides, the artists use to avoid stage fright on stage. Neurologists conditionnèrent recently volunteers just as was done with rats, by subjecting them to mild electric shocks associated with images of spiders. Brrr! Then we did take propranolol to half of them placing them pictures again and shock. The next day, subjects who took propranolol were much less afraid than others to the sight of spiders. The experiences of the previous day had left them but few clear memories of emotionally charged: they could not evoke the feeling of fear as opposed to other participants in the experiment. This kind of discovery of great interest all people suffering from post-traumatic stress after witnessing an accident or a particularly creepy scene. For years, they constantly relive the memory with an emotional intensity intact. Rather than trying to forget Kate Winslet, Jim Carrey would have done better to gorge on propranolol, it would have been more effective. Cinégénique less likely. Sources:
Jospeph Ledoux Manipulating Memory (The Scientist, 2003) on the experience and the theory of rebinding
Sandra Swanson, Memory and Forgetting (Dana Foundation, 2010)
Related posts:
you forgetting gold not to Be: the mysteries of oblivion
