Wednesday, September 25, 2013

The technology for rewriting the memories

Every time we retrieve something from our memory it can be changed, rewritten with new info and re-consolidated in the brain as a new, up-dated memory. There are specific time windows of this process that could be implemented into the extinction procedures used for the therapy of phobia and addiction.
The traditional view in psychology and also in neuroscience is a module-oriented approach: the amygdala relates to emotions, the hippocampus to memory, and the visual cortex to perception. Subsequently, the brain has been regarded as a “Swiss penknife”, each anatomical part being a specialized tool for a certain function. And these functions are ascertained by the psychology as “psychological processes” or “mental faculties”. Psychology textbooks are organized into chapters  according to these taxonomies – one chapter for emotions, one for perception, and one for memory. But what if this paradigm is wrong? Based on the acquired data in neuroscience various authors have implied that the mental faculties approach should be altered, pointing out the inaccuracy of this module-oriented organization of the brain.



From the very beginning, psychology and cognitive sciences in general, have investigated memory, dividing it into various subcomponents: sensory, short and long term, procedural and declarative, implicit and explicit, episodic and semantic. All these paradigms are based on the same definition of memory: the ability to encode, store and recall information. One fundamental aspect in this definition is that information is initially stored and subsequently revealed, in the same way a “refrigerator” assumes that a certain temperature prevents food from going bad. Nonetheless, experimental data has revealed that the ability to recall information is not independent from what we traditionally call “perception”, “imagination” or “attention”, but rather shares an intimate relation with them. The “perceptual-mnemonic” theory of the brain implies that it may not be constructive to make a distinction between “perception” and “memory” as mental functions, as they may seem to be from introspection. Instead, they should be regarded as different manifestations of a common neural substrate. There is a dynamic interaction between “perception” and “retrieval”. Subsequently, retrieval of information is similar to perception because it involves the identification and understanding of current stimuli according to past experiences. Some argue that we cannot see something if it does not resemble information from memory. An anecdotic example supporting this contention is the story of the native Americans that could not see the Spanish ships anchored onshore because they did not know anything about ships.
Experimental studies have shown that is possible to rewrite an old memory with new info, but first you have to be exposed to the context where that old memory was initially created. Actually this is happening when people who were witess to an accident or murder are exposed to information about that incident covered by the media, during the time interval they wait to testify in Court. Their original memories become automatically compromised by these new info. This re-exposure trigger a special labile state in the brain and memory updating is made only when the brain enters in this labile state and the new info is presented particulary in this state. It is fascinating ! It’s like a magic key from the Indiana Jones movies. Hence memory retrieval leads to new memories formation on the foundation of the stored and reactivated previous experience. Actually the reality is even more dramatic, being impossible to create new memories without reactivating past memories. Old memories act like an atractor which capture info from the same category with them and fix it like a superglue. Even more fascinating, studies revealed that there are specific time windows when it comes to change an existing memory. Most of this sort of studies were made for treating phobia and addiction. In order to overcome a phobia or an addiction, the brain has to re-learn rather than to erase the undesirable aversive or appetitive memories. This re-learning is called extinction and consist in the association of the context previously associated with the drugs of abuse or the unpleasant stimulus, with lack of drugs respectively with safeness. But in order to be effective, this extinction technique must obeys some specific rules. Hence, performing a spatial or contextual learning task 1 or 2 hours before the extinction training facilitates the effect of training. But not if the exposure was 3 hours before. Why ? Because this sort of learning produces proteins in the neurons and this proteins are captured by the synapses and used to consolidate the new memory created during the extinction training. The process is named tag-and-capture.  Furthermore, the extinction is effective only if procedes between 10 minutes and maximum 2 hours after the exposure to the traumatic context respectively the reactivation of the traumatic memory. Note the labile state of the brain induced by remembering/recognition, mentioned above. This is the time interval it stays labile and can incorporate new info into the existing one. Fructose or glucose consumption 30 minutes after the exposure/reactivation also helps. It is important to say that 2 hours after exposure/reactivation, the time window for the reconsolidation of the new memory is closing, and the behavioral effect could be noticed only after 2 days when the reconsolidation process is finished. This procedure could be resumed several times if is necesary, but the results obtained are garanteed at least 180 days. As you can see it’s a kind of engineering.

I conclude that knowing the real functional organization of the brain is a must if we want to explain the mind but especially if we want to positively impact its performance such as improving learning and re-learning.


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