Author Affiliations: Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
We thank Warren and colleagues for their insightful comments on the long-term representation of meaningful knowledge about music, objects, and quantities. We described a dissociation between object knowledge and knowledge of music meaning in a patient with SemD.1 In an attempt to use our observation to support a unifying characterization of the deficit in SemD, Warren et al forward the intriguing hypothesis that object knowledge is compromised in SemD because it depends on representations in the world, while formal music knowledge and number knowledge may be relatively preserved in SemD because these are self-contained semantic systems independent of world knowledge. This hypothesis may help explain the dissociation of music melody and notation from musical instruments and musically mediated emotion that Warren and colleagues recently observed.2 We described a double dissociation in SemD and corticobasal syndrome several years ago that may be interpreted as consistent with Warren's hypothesis; patients with SemD were relatively impaired on a measures of object knowledge, while patients with corticobasal syndrome were relatively impaired in number knowledge.3
Grossman M, Bonner MF, Weinstein J. Music and Semantic Dementia—Reply. Arch Neurol. 2011;68(8):1089-1090. doi:10.1001/archneurol.2011.196