The area of the brain that houses musical memories is less damaged by the disease. Without quite knowing why, music is one of the few weapons that therapists have to face the progression of Alzheimer's disease. Despite the devastation caused by this disease in the brain and, especially, in the memory, a great part of the patients keeps their musical memories, even in the later stages. Now a study shows the possible causes of this phenomenon: music is stored in areas of the brain different those in the rest of the memories.
The temporal lobe, the portion of the brain that runs the temple to the back of the ear, is, among other things, the disco of humans. There our auditory memory is managed, including the songs. Studies with people with brain injury support the idea that we keep music in a network centered in this area. However, the temporal lobe is also the first part of the brain to suffer the ravages of Alzheimer's disease. How is it then explained that many patients do not know their names or how to return home, but recognize that song that touched them decades ago? How are some patients unable to pronounce a word, but in the meantime, they can hum songs that were successful when they could still remember?
To try to answer these questions, researchers several European countries led by neuroscientists at the Max Planck Institute for Neuroscience and Human Cognition in Leipzig (Germany) carried out a double experiment. On the one hand, they looked for areas of the brain that are activated when we listen to music. On the other hand, once these areas were located, they analyzed whether, in Alzheimer's patients, such areas of the brain showed any signs of atrophy or, on the contrary, better resisted the disease.
To locate the brain stores the music, the researchers made thirty healthy individuals listen to 40 trios of songs. Each trio consisted of a well-known theme taken the charts since 1977, lullabies and traditional German music. The other two songs were, by style, tone, rhythm or mood, similar to the first, but were ed the group of musical failures so that they would not be known.
As explained in the Oxford University Brain magazine, the design of the experiment was based on the hypothesis that the experience of listening to music is, for the brain, different that of remembering it and in the two processes different brain networks operate. During the sessions, the volunteers' brain activity was recorded using the functional magnetic resonance (fMRI) technique. They found that music is housed in different areas of the brain than areas other memories are stored.
"At least the key aspects of musical memory are processed in areas of the brain that are not normally associated with episodic, semantic or autobiographical memory," says Jörn-Henrik Jacobsen, neuroscientist at Max Planck and co-author of the study. "But we have to be very cautious when we say something as absolute as that," he adds cautiously. The areas that showed greater activation when recalling the songs were the anterior cingulate gyrus, located in the middle region of the brain, and the pre-supplemental motor area, located in the frontal lobe.
Part of this prudence may come the methodology adopted for the second part of the research. The ideal would have been to be able to study the location of musical memories directly in Alzheimer's patients and not in healthy people. But, as Jacobsen points out, it is not easy to get a significant number of patients to participate in such work. In addition, there is also the problem that many of those affected were able to remember the song, but were unable to verbalize that memory. Therefore, a second experiment was carried out to see if the areas the music is stored are equally or less affected by the disease of forgetfulness.
The brain processes the experience of listening to music and musical memories in different zones
For this, 20 patients with Alzheimer's disease were studied and their results were compared with those of thirty other healthy individuals, both groups with a mean age of 68 years. The goal was to find out what state the musical areas were in compared to the rest of the brain. In the diagnosis and monitoring of the disease, mainly three biomarkers are used, one of them is the degree of deposition of the β-amyloid peptide, a molecule that tends to accumulate forming plaques in the early stages of the disease. Another clue is the alteration of glucose metabolism in the brain. And finally, cortical atrophy, a natural process as you get older, but in Alzheimer's disease it is more pronounced.
The measurements showed that the levels of beta-amyloid deposition did not show significant differences. In patients' musical areas, glucose metabolism was at normal levels and cortical atrophy was up to 50 times lower than in other areas of the brain. For Jacobsen, "showing lower hypometabolism and cortical atrophy compared to other areas of the brain means that they are not as affected in the course of the disease". And he adds. “But this can only be observed, I believe that nobody can explain why this is so. However, the anterior cingulate gyrus shows increased connectivity in Alzheimer's patients, which could even mean that it functions as a region that compensates for the loss of functionality of the others ”.
The most lasting memories are linked to an intense emotional experience, and music is very related to emotions
“The most lasting memories are those linked to an intense emotional experience and music has a close relationship with emotions; emotion is a gateway to remember ”, says the music therapist at the Alzheimer Spain Foundation, Fátima Pérez-Robledo. The study results confirm this. "Many patients don't remember the name of a relative, but they remember the lyrics of a song," she says.
In his daily work, Pérez-Robledo often acts as a DJ. If the patient is in an early stage, he himself suggests the songs that marked him. “In his musical history, we look for songs his childhood, adolescence, to evoke memories. Patients listen to them, dance or sing ”, says the therapist. When the patient can no longer tell which songs she likes, she experiences the most heard songs when she was a child or, as in many cases, it is the spouse who chooses that song they heard when they first met.