Brain Advance Access originally published online on March 31, 2009
Brain 2009 132(5):1277-1286; doi:10.1093/brain/awp055
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The amusic brain: in tune, out of key, and unaware
1 BRAMS Laboratory and Department of Psychology, University of Montreal, C.P. 6128, succ. Centre-ville, Montreal, Québec, Canada H3C 3J7 2 Cognitive Brain Research and Unit Helsinki Brain Research Centre, Department of Psychology, University of Helsinki, Helsinki, Finland
Isabelle Peretz, BRAMS Laboratory and Department of Psychology, University of Montreal, C.P. 6128, succ. Centre-ville, Montreal, Québec, Canada H3C 3J7 E-mail: isabelle.peretz{at}umontreal.ca
Like language, music engagement is universal, complex and present early in life. However, 
4% of the general population experiences a lifelong deficit in music perception that cannot be explained by hearing loss, brain damage, intellectual deficiencies or lack of exposure. This musical disorder, commonly known as tone-deafness and now termed congenital amusia, affects mostly the melodic pitch dimension. Congenital amusia is hereditary and is associated with abnormal grey and white matter in the auditory cortex and the inferior frontal cortex. In order to relate these anatomical anomalies to the behavioural expression of the disorder, we measured the electrical brain activity of amusic subjects and matched controls while they monitored melodies for the presence of pitch anomalies. Contrary to current reports, we show that the amusic brain can track quarter-tone pitch differences, exhibiting an early right-lateralized negative brain response. This suggests near-normal neural processing of musical pitch incongruities in congenital amusia. It is important because it reveals that the amusic brain is equipped with the essential neural circuitry to perceive fine-grained pitch differences. What distinguishes the amusic from the normal brain is the limited awareness of this ability and the lack of responsiveness to the semitone changes that violate musical keys. These findings suggest that, in the amusic brain, the neural pitch representation cannot make contact with musical pitch knowledge along the auditory-frontal neural pathway.
Key Words: congenital amusia; conscious awareness; pitch perception; auditory ERPs; melodies
Abbreviations: ERAN, early right anterior negativity; ERPs, event-related potentials; IFG, inferior frontal gyrus; MBEA, Montreal battery of evaluation of amusia; MRI, magnetic resonance imaging; VBM, voxel-based morphometry
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Received June 10, 2008. Revised January 12, 2009. Accepted February 13, 2009.
*These authors contributed equally to this work.
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