Dissociations among functional subsystems governing melody recognition after right-hemisphere damage

This study describes an amateur musician, KB, who became amusic following a right-hemisphere stroke. A series of assessments conducted post-stroke rev ealed that KB functioned in the normal range for most verbal skills. Howeve r, compared with controls matched in age and music training, KB showed seve re loss of pitch and rhythmic processing abilities. His ability to recognis e and identify familiar instrumental melodies was also lost. Despite these deficits, KB performed remarkably well when asked to recognise and identify familiar song melodies presented without accompanying lyrics. This dissoci ation between the ability to recognise/identify song vs. instrumental melod ies was replicated across different sets of musical materials, including ne wly learned melodies. Analyses of the acoustical and musical features of so ng and instrumental melodies discounted an explanation of the dissociation based on these features alone. Rather, the results suggest a functional dis sociation resulting from a focal brain lesion. We propose that, in the case of song melodies, there remains sufficient activation in KB's melody analy sis system to coactivate an intact representation of both associative infor mation and the lyrics in the speech lexicon, making recognition and identif ication possible. In the case of instrumental melodies, no such associative processes exist; thus recognition and identification do not occur.