(After a two-week holiday break, John Medina’s Brain Rules resumes with this entry. You may recall we are discussing how the brain processes auditory information, I am currently giving you an earful about how the brain perceives music).
Think of your favorite song.
Now imagine that song collapsing to a single garbled note. Or just a flattened monotone. Or just an indiscriminate noise. No melodic line, no rhythm, no harmony.
This is the musical reality for people born with brains that will never allow them to perceive music. All they will hear when music plays - all they will ever hear when music plays - is disorganized sound. It may be an inspiring composition to us, but congenital cacophony to them. Give this phenomenon its own tongue-twisting label: congenital amusia.
There are two puzzling aspects to congenital amusia. First, every aspect of musical perception can be affected, from melody to meter to rhythm. Second, every other aspect of auditory processing can be perfectly preserved, including speech. These puzzles originate at birth, hence the word “congenital.”
I wrote about one such person in my book Brain Rules. “Monica” is a high functioning nurse who came to science because, as they say, she could not carry a tune in a bucket. Neither could other family members. Curiously, every other facet of Monica’s hearing measured normally.
Just not if the sound involved music. The paper that first described her put it this way:
“Monica suffers from a life- long inability to recognize or perceive music, sing, or dance.”
One clear deficit was pitch discrimination. Pitch, as you may recall, is the frequency of a given sound wave. It’s why we think a note is either “low” or “high”. Monica has no pitch discrimination, which means she cannot hear when a note is “low” or “high” or when it is going low or high. As a result, music appears as a flattened monotone.
Monica also cannot detect changes in the patterned placement of sound over time, which means she has problems perceiving beats. No ability to discriminate melodic structures and no ability to discriminate rhythmic patterns means Monica has “amusia” with a capital A.
Another puzzling aspect of Monica’s auditory experience is that her speech production (and speech perception) is completely unaffected. When she asks a question, her voice goes up normally. She can absolutely hear the difference. When she finishes a sentence, her voice goes down. She can absolutely hear that difference, too. The perception is preserved even when the source is not her voice. She displays typical pitch and rhythmic discrimination if her brain decides what she is hearing is NOT music.
Many cases of congenital amusia have been described since Monica’s case was published. So has acquired amusia, which are deficits originating not by accident of birth, but by accident of environment (stroke being a common source).
These data point to an extraordinary fact. You have an actual music module in your brain. Its day job appears to be processing music. This module is separate from nearly every other auditory processing experience, including speech and language. If the music module becomes damaged, other aspects of sound perception can remain unaffected.
For the next few entries, we’re going to see if we can make sense of people like Monica. By all means, give a thought to them next time you enjoy your favorite tune. They live in an auditory world very different from most people.
REFERENCES
Peretz, I., et al. "Congenital Amusia: A Disorder of Fine-Grained Pitch Discrimination." Neuron 33 (2002): 185-91.
Szyfter, K., and J. Wigowska-Sowińska. "Congenital Amusia—Pathology of Musical Disorder." J Appl Genet 63, no. 1 (2021): 127-31.
Geschwind, N. "The Brain of a Learning-disabled Individual." Ann Dyslexia 3 (1984)4: 319-327.