Why musical memory can be preserved in advanced Alzheimer’s disease

Abstract

) for a scientific commentary on this article.Musical memory is considered to be partly independent from other memory systems. In Alzheimer's disease and different types of dementia, musical memory is surprisingly robust, and likewise for brain lesions affecting other kinds of memory. However, the mechanisms and neural substrates of musical memory remain poorly understood. In a group of 32 normal young human subjects (16 male and 16 female, mean age of 28.0 AE 2.2 years), we performed a 7 T functional magnetic resonance imaging study of brain responses to music excerpts that were unknown, recently known (heard an hour before scanning), and long-known. We used multivariate pattern classification to identify brain regions that encode long-term musical memory. The results showed a crucial role for the caudal anterior cingulate and the ventral pre-supplementary motor area in the neural encoding of long-known as compared with recently known and unknown music. In the second part of the study, we analysed data of three essential Alzheimer's disease biomarkers in a region of interest derived from our musical memory findings (caudal anterior cingulate cortex and ventral pre-supplementary motor area) in 20 patients with Alzheimer's disease (10 male and 10 female, mean age of 68.9 AE 9.0 years) and 34 healthy control subjects (14 male and 20 female, mean age of 68.1 AE 7.2 years). Interestingly, the regions identified to encode musical memory corresponded to areas that showed substantially minimal cortical atrophy (as measured with magnetic resonance imaging), and minimal disruption of glucose-metabolism (as measured with 18 F-fluorodeoxyglucose positron emission tomography), as compared to the rest of the brain. However, amyloid-b deposition (as measured with 18 F-flobetapir positron emission tomography) within the currently observed regions of interest was not substantially less than in the rest of the brain, which suggests that the regions of interest were still in a very early stage of the expected course of biomarker development in these regions (amyloid accumulation ! hypometabolism ! cortical atrophy) and therefore relatively well preserved. Given the observed overlap of musical memory regions with areas that are relatively spared in Alzheimer's disease, the current findings may thus explain the surprising preservation of musical memory in this neurodegenerative disease.

Music and Brain Plasticity: How Sounds Trigger Neurogenerative Adaptations

“…Music, in this case, has been reported as one of the domains in which general skill and memory are preserved in spite of otherwise severe impairment [90]. This preserved musical processing, moreover, is not limited to procedural memory but often includes also stories of music, which can be used as an effective mnemonic device [91].…”

Music: The Last Thing We Forget

“…Interestingly, the amount of sticky buildup in the MMA was not significantly lower than in other parts of the brain (fourth row, Figure 2) [5]. AD progression typically goes from sticky buildup  decreased sugar uptake  shrinkage throughout the brain, with the sticky buildup sometimes appearing even before noticeable memory loss [4].…”

“…To answer this question, researchers recorded the brain responses of 32 healthy young adults as they listened to carefully pre-selected snippets of well-known, recently known, and completely unknown pieces of music [5]. The well-known pieces were selected from songs that were in the Top 10 between 1977 and 2007, nursery rhymes, and oldies, while the unknown songs were selected by looking at people's listening habits and choices on Amazon and Pandora.…”

“…Adapted from Ref. [5] with permission. Figure 2 form of dementia, and it most frequently afflicts people close to your grandparents' age.…”

“…This brings us to the second, third, and fourth rows of Figure 2. After identifying the MMA in healthy young adults (top row), the researchers took MRI and PET scans of 20 individuals with AD who did not have musical training [5]. They found that the MMA showed some of the lowest amounts of shrinkage and it was still getting enough sugar to function properly (second and third rows, Figure 2).…”