Congenital amusia is a neurological disorder of music perception, cognition and appreciation. In this ERP study, Braun and colleagues obtained a late positive brain response (ERP) to the final out-of-scale notes of well-known tunes both in controls and amusic subjects, whereas they observed an early negative response to those notes in controls only. Based on those results, the authors make the interesting suggestion that the amusic brain may detect melodic errors without awareness. However, the observed auditory ERPs tell a different story. The presence of P300 without early anterior negativity suggests that the amusic brain was able to consciously detect the large pitch errors, as early negativities typically index automatic processing whereas the P300 reflects post-decisional conscious processes (e.g. it follows the motor response of the stimulus detection; Goodin, Aminoff, & Mantle, 1987). Comatose patients may also have a P300 just before awakening, but it typically follows the generation of an early negativity (Vanhaudenhuyse, Laureys, & Perrin, 2008). Even in blindsight, a condition to which Braun et al. compare amusia, no P300 has been found without some residual discrimination (cf Weiskrantz, 2008; Weiskrantz, Rao, Hodinott-Hill, Nobre, & Cowey, 2003). The current issue of unaware processing of melodic errors in amusics can only be solved by collecting behavioral data along with ERP recordings (cf. Seth et al., 2008). For instance, we cannot know if these individuals were able to detect some of the melodic changes, such as those that are larger than 2 semitones and that can be detected by amusics (Hyde & Peretz, 2004). Information on the severity of behavioral melodic deficit is also missing. All these issues are left unanswered by Braun et al. (2008); hence any conclusion at present cannot be but open.

by Elvira Brattico & Isabelle Peretz


References
Goodin, D.S., Aminoff, M.J., & Mantle, M.M. (1987). Sensory discrimination and its relationship to the cerebral processing of infrequent stimuli. Can J Neurol Sci, 14(4), 642-8.
Seth, A.K., Dienes, Z., Cleeremans, A., Overgaard, M., Pessoa, L. (2008). Measuring consciousness: Relating behavioral and neurophysiological approaches. Trends Cogn Sci, 12, 314-321.
Vanhaudenhuyse, A., Laureys, S., & Perrin, F. (2008). Cognitive event-related potentials in comatose and post-comatose states. Neurocrit Care, 8(2), 262-70.
Weiskrantz, L. (2008). Is blindsight just degraded normal vision? Exp Brain Res.
Weiskrantz, L., Rao, A., Hodinott-Hill, I., Nobre, A.C., & Cowey, A. (2003). Brain potentials associated with conscious aftereffects induced by unseen stimuli in a blindsight subject. Proc Natl Acad Sci U S A, 100(18), 10500-5.