An Injured Brain is Out of Tune
The brain is arguably our most valuable organ so it is important to keep it safe. Despite advances in safety and technology, it is unfortunately not possible to protect our brain at all times. Even if you live your life in a bubble, like that one Seinfeld episode, the possibility of suffering a traumatic brain injury still exists from a bad fall.
But let’s not get ahead of ourselves (pun intended). Caused by an outside force, traumatic brain injuries (TBI) can leave a person with a wide array of deficits on things such as cognitive function, balance and vision, and even our music and speech perception. Laurene Leard-Schneider and Yohana Leveque explored the relationship between people who suffered TBIs and the potential musical and prosody impairments they may suffer (2021). If you’ve just read the last few sentences and are thinking to yourself “I have no idea what he is talking about” then keep reading, it will all be explained! The researchers hypothesized that impairments in music would be correlated with impairments in prosody perception and that the linguistic and emotional dimensions of prosody would be associated with each other.
Before we jump into the study, I want to ensure we are all on the same page about some terms that will be helpful to keep in mind. Amusia is a fairly uncommon musical disorder. People with amusia have a difficult time noticing when music is out of tune. This involves deficits when trying to detect deviations in pitch smaller than two semitones and therefore fail to detect wrong notes (Peretz, 2016). In congenital amusia, understanding of prosody generally remains intact. Prosody is the little nuances we add to our speech that help to give it more meaning. Some common characteristics are rhythm, intonation and stress applied to the sound being made. Sarcasm is a great example of how we use prosody to change the meaning of a sentence. For example if it’s bright and sunny out, you might say “wow what a great day!” However, if it’s rainy and gloomy out you might also say “wow, what a great day…” but think about how you might say that. That’s prosody! Now that that’s out of the way let’s get back to the paper.
For their study, Leard-Schneider and Leveque recruited native French speakers between the age of 18–60 who had suffered a severe traumatic brain injury. Patients included in the study were given some pretests in order to ensure that they would be able to complete the actual tests needed for the study. Ultimately, 31 patients ended up completing six tests. To assess musical perception (a.k.a amusia), participants completed two parts of a standard musical deficits test known as the Montreal Battery of Evaluation of Amusia (MBEA) to assess pitch and rhythm perception. If you yourself would like to take the test yourself just click below!
In the first subtest, the Scale subtest, participants were given two short musical sequences and asked to determine if they were identical or different. Melodies that were different varied by only one note. The Rhythm subtest was set up the same way except the different melodies varied in terms of rhythm, as the name implies. After these tests were administered patients were tested on their perception of prosody. Two parts of a test that determines language impairments and communication disorders known as the Montreal Evaluation of Communication (MEC), specifically the Emotional Prosody Understanding and the Linguistic Prosody Understanding subtests were used to gather data. To further support these tests were also run to further gauge participants’ recognition of both emotional and linguistic prosody perception which were the Emo Vowel and Lin Vowel tests respectively.
After all of these tests were performed, Leard-Schneider and Leveque dove into the data and split the participants up into two groups, amusic and non-amusic, using the scores from the MBEA subtests. Their main findings was that amusia is fairly frequent among patients with TBI, considering 42% of patients in their sample presented as amusic. To expand on that, amusia seems to be a long lasting deficit following severe TBI. Another association with TBI is that patients also frequently experience impairments in emotional and linguistic prosody decoding with, respectively, 42% and 55% of patients experiencing significant deficits. However, more prosody deficits were found in amsuic patients than in non-amusic patients which, in congenital amusia, prosodic deficits do not normally occur (Peretz, 2016). One explanation for this is that people with congenital amusia learn to exist with their musical deficit while acquired amusia takes away an ability that previously existed.
Although the authors’ received significant results, they do give a word of warning. First of all, they did not ever officially distinguish if patients might have had congenital amusia. This finding may skew some of the results had it turned out that one of the patients had amusia before their TBI. The authors also mention that, while the MBEA tests they use tend to be the most reliable, they did not use the whole test. This was done to prevent patient fatigue but the full set of tests might yield different results in terms of whether or not a patient has amusia. Finally, Leard-Schneider and Leveque also mention that it is possible that disorders of working memory and attention might have led to lower scores on the tests performed. The researchers bring up the point that all patients were able to succeed in at least one task, indicating that their attention and working memory were intact, but the fact that this wasn’t specifically checked adds room for error.
Ultimately, what Leard-Schneider and Leveque were able to show with this paper is that it’s not uncommon to see difficulties perceiving music and prosody after a TBI. This deficit can persist for years after the injury occured as well. It is interesting to note that in a review of previous publications, Sihvonen and colleagues actually found that the use of music with other brain conditions, such as parkinson’s or a stroke, can actually help to improve symptoms (2017). I find it so fascinating that different deficits in the brain could have different responses to the same stimulus. Strokes and TBIs alike can be fairly general and occur almost anywhere in the brain so why such a different response to music? Is it possible to still see the benefits of music on rehabilitation in an amusic patient? Just another fascinating question on the human brain’s journey to understanding itself.
References
Léard-Schneider, L., & Lévêque, Y. (2021). Perception of music and speech prosody after severe traumatic brain injury. Music Perception, 39(2), 103–117. https://doi.org/10.1525/mp.2021.39.2.103
Peretz, I. (2016). Neurobiology of congenital amusia. Trends in Cognitive Sciences, 20(11), 857–867. https://doi.org/10.1016/j.tics.2016.09.002
Sihvonen, A. J., Särkämö, T., Leo, V., Tervaniemi, M., Altenmüller, E., & Soinila, S. (2017). Music-based interventions in neurological rehabilitation. The Lancet Neurology, 16(8), 648–660. https://doi.org/10.1016/s1474-4422(17)30168-0
