According to the Journal of Neuroscience, tone deafness could be caused by a very particular brain defect.
“This region, a neural ‘highway’ called the arcuate fasciculus, is known to be involved in linking music and language perception with vocal production.The arcuate fasciculus was smaller in volume and had a lower fiber count in the tone-deaf individuals. More notably, the superior branch of the arcuate fasciculus in the right hemisphere could not be detected in the tone-deaf individuals. The researchers speculated that this could mean the branch is missing entirely, or is so abnormally deformed that it appears invisible to even the most advanced neuroimaging methods.”
Tone deafness, also known as amusia, dysmelodia and dysmusia is a disorder where a listener finds it impossible to hear relative differences between notes.
Test For Tone Deafness [site]
In our research, we were looking for neuro-anatomical correlates of tonedeafness (called ‘congenital amusia’ in the scientific literature. We gave several dozen subjects a high-resolution MRI scan and used a statistical package to analyze the images. This technique, called VBM (voxel-based morphometry), has been used to study the changes in the brain caused by Alzheimer disease and many other neurological conditions. The test you are about to take was used as a screening test to roughly characterize patient’s pitch discrimination and musical memory abilities. Even though musical memory is strongly tested here, we have found that people who are tonedeaf tend to have normal musical memories.
Amusia and Music Appreciation [site]
Though most amusia sufferers find listening to music pointless, some even find it annoying and unpleasant.
Anne Vere, an amusic from Newcastle, describes music as an ‘irritant’. When she heard the theme tune to Brief Encounter, voted the UK’s favourite piece of classic music for the past five years, she described it as ‘banging that would be best avoided’.
About 4% of the Planet is Truly Tone Deaf [site]
Amusia (commonly referred to as tone-deafness) is a difficulty in discriminating pitch changes in melodies that affects around 4% of the human population. Amusia cannot be explained as a simple sensory impairment. Here we show that amusia is strongly related to a deficit in spatial processing in adults.
Amusia and it’s Effect on Language [site]
‘Music is probably the only domain in which fine-grained pitch discrimination is required for its appreciation,’ report Julie Ayotte, Isabelle Peretz, and Krista Hyde in a tone-deaf study. Accordingly, a ‘degraded pitch perception system’ may compromise music perception but leave speech intonation relatively unaffected. ‘Yet, the same pitch-tracking mechanism may subserve both domains,’ they conclude.
We often think of ‘tone deafness’ in its lay meaning — ‘unable to carry a tune or sing a song.’ That’s different from the medical meaning of “inability to distinguish successive tones.” Almost all people (except the medically tone deaf) can learn to sing with training.
Amusia’s Effect on Daily Life [site]
…congenital amusia is related to severe deficiencies in processing pitch variations. The deficit extends to impairments in music memory and recognition as well as in singing and the ability to tap in time to music. Interestingly, the disorder appears specific to the musical domain. Congenital amusical individuals process and recognize speech, including speech prosody, common environmental sounds and human voices, as well as control subjects. Thus, the present study convincingly demonstrates the existence of congenital amusia as a new class of learning disabilities that affect musical abilities.