As everyone already knows, Alzheimer's is characterized above all by the memory loss, supposedly irreversible.
And I say supposed, because until now we blindly thought that this memory loss, these erased memories, were forever. Proteins accumulated in the brain of someone with Alzheimer's (both the beta-amyloid like the increasingly important protein tau) let us glimpse that their ills were irreparable. But they are not.
At least, that is what a recent study published in the prestigious Nature, chaired by Nobel laureate Susumu Tonegawa: Alzheimer's memory loss is reversible; in other words, it is possible to recover the memories lost in the disease.
Alzheimer's Memory Loss Can Be Recovered
According to Tonegawa and his colleagues, this characteristic Alzheimer's memory loss could recover, at least in the early stages of the disease. These memories never really disappear from the brain, but we simply cannot access them. In the same way that with the passage of the years we accumulate memories and each time we find it harder to remember some things (although they are always there), Alzheimer interrupts this memory system even more.
To demonstrate their theory, this group of researchers used two groups of mice: one group genetically modified to suffer from Alzheimer's disease in its early stages, and another group of healthy mice. They placed all the rodents in an area where they would receive electric shocks. Obviously, when they put the mice back in the same dump box, they were scared. After days passed, only healthy mice experienced this fear (mice with Alzheimer's had forgotten the fear).
In a second part of the experiment, the researchers used the technique of optogenetic: Genetically modified mice neurons to be sensitive to light. Specifically, the experiment focused on the area of the hippocampal toothed gyrus, related to the reactivation of experiences when recalling them (ultimately, the area responsible for retrieving memories).
By using light over this area, Alzheimer's mice recall their fear of electric shock. Unfortunately, the memory faded when you stopped applying light, returning the dreaded memory loss to rodents.
The brain areas responsible for memory
According to the researchers, fear was recorded in memory thanks to the reinforcement of the neural connections between the dentate gyrus and another area called the entorhinal cortex (just behind the temple, to give you an idea). If light pulses were applied to this brain region, they also reversed memory loss in the mice. If light pulses were combined in both areas (dentate gyrus and entorhinal cortex), long-term recovery was possible, even reaching the level of healthy mice.
But, yes, the researchers point out the need to be specific in the use of the optogenetic technique using light: If they used light pulses indiscriminately over the area of the dentate gyrus, they did not obtain the recovery of memories. They had to direct light specifically to the neural circuits involved in recording memories. And always talking about early stages of Alzheimer's; At more advanced stages, as far as we know to date, memory loss may be irreversible.
Complications of reversing memory loss in humans
As you may have verified, throughout the experiment the optogenetic, a technique that in humans today it is impossible (In fact, it has never been done because it would not be ethical). Such a technique requires opening the skull and genetically modifying cells. No, it is not very feasible to use it in humans, and the researchers are quite clear about it.
The alternative they propose will be the use of deep brain stimulationThis therapy has been used in humans and seems to have good results in various mental and neurological disorders such as epilepsy or Parkinson's. They have even proposed the use of certain drugs that imitate the benefits of optogenetics to reverse memory loss. But, for now, these are just futuristic ideas.