Wednesday, December 18, 2013

Saving your memories save your brain

The brain’s ability to preserve memories lies at the heart of our human experience and also of our identity. This is why forgetting is one of our most dangerous enemies. Diseases like Alzheimer delete our identity and make our life impossible. But we don’t have to get some of these debilitating illnesses to have problems. We are our memories and anytime we are not able to remember some experiences we lived in the past we feel like losing parts of our life. Recent findings show the fate of memories and also suggest the possible role of psychotherapy. And more…

But where in the brain do those old memories go? Despite decades studying how the brain transforms memories over time, neuroscientists remain divided over the answer. This month, researchers from Johns Hopkins University have come up with a new theory that might clear up this controversy. They claim that what we do with a memory determines where it is stored in the brain. Their theory, called Competitive Trace Theory (or CTT), suggests that what really matters is how often we revisit the memory. Memories they say are transformed each time we revisit them. A memory is first encoded by the activity of neurons from one part of the brain called the hippocampus. The hippocampus acts like as the brain’s director, telling the cortex which particular neurons to activate (see in the bellow image the structures presented in green – hippocampus and cortex). Each time we recall that memory, a similar but not identical set of neurons are activated. Neurons that are frequently activated became part of the permanent memory trace in the cortex, while the rarely activated ones are lost. Every reactivation re-encodes the memory, and depending on what cortical neurons are engaged, can strengthen, weaken or up-date particular memory features. With each memory reactivation, some features are reinforced while others disappear, explaining why the memory seems to get fuzzy over time. And the more details that are lost, the less “episodic” and the more “semantic” the memory becomes, explaining the sense of personal detachment often associated with very old memories. As memories get older, they are decontextualized due to competition among partially overlapping traces and become more semantic and reliant on cortex storage. Consolidation that leads to the strengthening of memories enhances conceptual knowledge (and becoming semantic memories) at the expense of vivid contextual details (or episodic memories).

Therapists working with traumatic patients know this very well – there is a clear distinction between recent traumas and distant traumas. Actually psychotherapy helps in this way : when a memory is recalled often it will more rapidly become stored in the cortex, become less episodic and independent of the hippocampus while a memory that’s rarely revisited will remain dependent on the hippocampus. As a result, remote memories are more likely to have a stronger semantic representation but also to be less vivid and more likely to include illusory details. And this is how it can incorporate a new perspective, a less emotional and more rational one, built by the joined efforts of the patient and the therapist.
Above I pointed out that each time we recall a memory a  set of neurons are activated, and neurons that are frequently activated became part of the permanent memory trace in the cortex, while the rarely activated ones are lost. In a recently published review, I present evidence that learning based on hippocampus seems to trigger the DNA repair pathways inside those hippocampal neurons, if the subject is re-exposed to the previously learnt information. So every time we encounter (or generally recall) some previously experienced contextual memories (a memory linked with a specific situation) the neurons involved in that memories seems to repair themselves and become healthier. And hence live longer. The new theory described above suggests that this process also save the memories stored in those neurons, the hippocampus activating the cortex and sending that data to it. Maybe the DNA repair process associated with this data transfer helps to clean up the hippocampus in order to be ready to learn something new. Something like a refresh process. Refresh that doesn’t happened in Alzheimer patients and other forms of dementia.

So revisiting your past can save your memories and also your brain.

Friday, December 6, 2013

The creative brain

Everybody knows that the left hemisphere of the brain is realistic, analytical, organized and logical, and the right hemisphere is creative, emotional, and intuitive. But in reality there is no such thing. These are only myths. In the early days of neuroscience some people claim that there are specific centers for creativity in the brain - like the temporal lobe, while other voices said is critical the interconnectivity between the two hemispheres made by the corpus callosum. But there are more speculations than scientific data. So, is there a place in the brain for creativity? And why should I be interested in the answer of these questions?

The latest findings from neuroscience suggest that the right brain/left brain distinction is not correct when it comes to understanding how creativity works in the brain. Creativity does not involve a single brain region or a single side of the brain. The entire creative process from preparation to incubation to illumination and verification consists of many interacting cognitive processes and emotions. Creation is a multi-step process not “an insight”. It takes time, sometimes weeks or even months, and depends by many factors, starting with your experiences and ending with the environment where you create. Depending on the stage of the creative process, and what you are actually trying to create, different brain networks are recruited to handle the task. Furthermore, many of these brain networks play as a team to get the job done, and recruit brain structures from both the left and right hemisphere.
And now I will be more specific. Let’s talk about some brain networks. Converging research do suggest that creativity recruits brain regions that are involved in many stuff like daydreaming, imagining the future, remembering personal memories, making meaning, and social cognition. It is known that all these processes are implemented by a specific neural network called Default network distributed on vast areas within the prefrontal, parietal and temporal lobes (see the picture bellow with yellow the Default network). Different studies documented that this network is responsible for constructing mental simulations based on personal experiences, thinking about the future, and generally when imaging alternative perspectives and scenarios to the present. It’s interesting that this Default network is associated with everything that the subjective Self entails. Hence, it is involved in introspection – when people are asked to describe their personality traits or present emotional state (disgust, fear, sadness, fury, happiness), to recall a past personal experience or to talk about their attitudes or preferences. This network is emotional by excellence, being implicated in the evaluation of objects described as positive/desirable or negative/undesirable, and the evaluation of emotionally-charged movie sequences. Also it is involved in social cognition. Studies revealed that one common element between the processes occurring within the Default network is the analysis of complex interactions between humans perceived as social, interactive and emotional in the same way as we perceive ourselves to be. It is involved in deducing the mental states of other people and is active when people make attributions regarding another person’s behavior, when they form a first impression about someone or when playing competitive games against another person (but not against a computer).
Well, imagistic studies (using fMRI) made on jazz musicians and rappers engaging in creative improvisation revealed that this Default network is highly active. When you want to loosen your associations, allow your mind to roam free, imagine new possibilities is good to increase activation in this network. So, let’s called this Default network the Imagination network.


Now I introduce to you another brain network - the Attentional Control network (see the picture above with blue). It is recruited when a task requires that the spotlight of attention is focused like a laser beam. This network is active when you’re concentrating on something challenging, or engaging in complex problem solving and reasoning that puts heavy demands on your working memory. This network is like a highway facilitating communication between frontal cortex and the posterior part of the brain. During the creative process is good to reduce activation of the Attentional Control network – or the inner critic – but, as we will see, not completely.
And here is the interesting part. Usually when you try to fix something, to solve a problem your Default network is OFF and the Attentional Control network is ON. But studies using fMRI revealed that creative people when attempting to solve a problem are able to activate both networks simultaneously, screening the environment and also letting open the door to the inner Self. This duality is critical. Why? Because an hyperactive Default network provides maximum flexibility in thinking and leads to creativity but is also a hallmark of mental illness such as manic-depression and schizophrenia. If you didn’t know, many of the artists were suffering by these diseases, especially by the first one. An hyperactive Default network gives you wings but also destroys you. In order to be really fruitful, the creative process has to be anchored in reality. You must be able to critically analyze the results of the creative process and to judge their relevance. But also to protect yourself, or in other words, to remain connected with this world. And this is done by the Attentional Control network which acts like a film critic.
            The good news is that both networks can be developed. The Default network actually grows if you exposed yourself to new experiences, but also can be trained by some meditation techniques like mindfulness. Attentional Control network can also be trained by using specific cognitive exercises like focused attention and working memory tasks. Knowing how your brain works gives you the advantage of choosing the wright path of personal development.