One of the most striking effects of music is witnessed in how it seems to preserve functions that are otherwise lost. There are numerous accounts of Alzheimer’s patients who have lost most of their memory, but can still recall songs with ease, or of aphasic patients who have lost their speech abilities but have no trouble singing. What does research say about the mechanisms that underlie these remarkable accounts?
In the case of Alzheimer’s, it seems that memory for music is in many ways distinct from memory for other things. For example, patients with severe damage to brain areas important for memory functions have been found to be able to create new memories of music. And vice versa, in 1996, an acclaimed researcher in the field of the neuroscience of music, Isable Peretz, reported a case study of an individual who had otherwise normal memory function, but could no longer recognize once-familiar music or form new memories of music after damage to temporal areas of the brain. Therefore, it could be that in Alzheimer’s patients who retain musical memory, the disease affects only areas that are crucial for forming other types of memories, but not musical ones. This means that the formation of musical memories relies on neural systems that are somewhat distinct from neural systems that underlie formation of other memories.
So what is the musical memory system like? Relatively little is known. Recently, researcher Jörn-Henrik Jacobsen and colleagues published an interesting article on brain areas important for musical memory and how these areas are affected by Alzheimer’s disease. In this study, 32 healthy individuals listened to songs of varying familiarity, and were asked to rate the songs in terms of whether they recognized them, how much they liked them, and whether the songs had any connections to previous life events. The researchers then looked at which brain areas were active while retrieving memories of the music. The most important of these areas were the ventral pre-supplementary motor area (SMA), and the caudal anterior cingulate gyrus. These areas have been associated with higher cognitive functions such as planning, decision-making, and learning.
The researchers then compared their results on the areas important for musical memory with images of brain damage associated with Alzheimer’s disease. The results were astonishing - the degeneration of brain areas characteristic of Alzheimer’s disease showed no overlap with the areas that were important for long term musical memory encoding! This means that for some reason, the areas important for forming musical memory are preserved for a long time in Alzheimer’s although areas important for other types of memory are not. Music can therefore provide an important and enjoyable way to access the well-functioning aspects of cognition in individuals with Alzheimer’s.
Another interesting case that resembles the memory-sparing nature of music is the recovery of speech with the help of singing in aphasia. Aphasia is a condition that is often caused by brain injury, most often stroke, resulting in the loss of verbal communication ability. This may include difficulties in understanding others, in expressing oneself verbally, in reading and in writing. Singing seems to help individuals who have trouble in producing, but not necessarily understanding, language. This discovery has led to the development of something called as Melodic Intonation Therapy (MIT). In this therapy, singing and rhythmic tapping are used to help the patient find words and repeat phrases. Here is a short video demonstrating this technique. The effectiveness of this therapy has not yet been fully demonstrated, and there is ongoing discussion on why it may work, its underlying neural correlates, and which aspects of the therapy specifically help in rehabilitation.
A recently published, randomized controlled study provided encouraging evidence on the effectiveness of MIT. In the study, 27 stroke patients with aphasia were divided into a group who received MIT five hours a day for six weeks, and into a control group receiving only standard care for the same amount of time. After the six weeks, the group of patients who had received MIT showed more improvement in language repetition abilities than the control group, as well as greater improvement in verbal communication. More randomized controlled studies are needed to corroborate these results. However, the study marks an important step in investigating the effectiveness of MIT, and understanding the positive effects so many have experienced.
But what specifically about MIT makes it effective? According to a study it may not actually be the singing, but rather rhythm that matters the most. In the study, researchers compared the effects of rhythmic speaking and melodic intonation. The participants were 17 stroke patients with severe difficulties in speech production, and were asked to sing or speak along to a playback of a pre-recorded voice. Experts then evaluated how accurately patients were able to produce speech. According to results, rhythmic speaking yielded better results than melodic intonation, leading the researchers speculate that the positive effects of MIT may therefore actually stem from rhythm. This link between speech and musical rhythm has been reported elsewhere too. For instance, as summarized in previous posts, research has found intriguing links between rhythm, speech production as well as speech perception. Perhaps because of these links, music training has been found to offer valuable support in the treatment of other language impairments in addition to aphasia, such as dyslexia.
In summary, results like these show the many ways by which music can tap into important cognitive resources otherwise inaccessible in patients with memory and language impairments. Perhaps in the future, music will become an integral part of the standard care provided for conditions like Alzheimer’s and aphasia.
written by marko ahtisaari
Hurkmans, J., de Bruijn, M., Boonstra, A. M., Jonkers, R., Bastiaanse, R., Arendzen, H., & Reinders-Messelink, H. A. (2012). Music in the treatment of neurological language and speech disorders: A systematic review. Aphasiology, 26(1), 1–19. doi:10.1080/02687038.2011.602514
Peretz, I. (1996). Can We Lose Memory for Music? A Case of Music Agnosia in a Nonmusician. Journal of Cognitive Neuroscience, 8(6), 481–496. doi:10.1162/jocn.19184.108.40.2061
Stahl, B., Kotz, S. A., Henseler, I., Turner, R., & Geyer, S. (2011). Rhythm in disguise: why singing may not hold the key to recovery from aphasia. Brain, 134(10), 3083–3093. doi:10.1093/brain/awr240
Van der Meulen, I., van de Sandt-Koenderman, W. M. E., Heijenbrok-Kal, M. H., Visch-Brink, E. G., & Ribbers, G. M. (2014). The Efficacy and Timing of Melodic Intonation Therapy in Subacute Aphasia. Neurorehabilitation and Neural Repair, 28(6), 536–544. doi:10.1177/1545968313517753