Examining pitch and numerical magnitude processing in congenital amusia: A quasi-experimental pilot study

ABSTRACT

Introduction: Congenital amusia is a developmental disorder associated with deficits in pitch height discrimination or in integrating pitch sequences into melodies. This quasi-experimental pilot study investigated whether there is an association between pitch and numerical processing deficits in congenital amusia. Since pitch height discrimination is considered a form of magnitude processing, we investigated whether individuals with amusia present an impairment in numerical magnitude processing, which would reflect damage to a generalized magnitude system. Alternatively, we investigated whether the numerical processing deficit would reflect a disconnection between nonsymbolic and symbolic number representations. Method: This study was conducted with 11 adult individuals with congenital amusia and a control comparison group of 6 typically developing individuals. Participants performed nonsymbolic and symbolic magnitude comparisons and number line tasks. Results were available from previous testing using the Montreal Battery of Evaluation of Amusia (MBEA) and a pitch change detection task (PCD). Results: Compared to the controls, individuals with amusia exhibited no significant differences in their performance on both the number line and the nonsymbolic magnitude tasks. Nevertheless, they showed significantly worse performance on the symbolic magnitude task. Moreover, individuals with congenital amusia, who presented worse performance in the Meter subtest, also presented less precise nonsymbolic numerical representation. Conclusions: The relationship between meter and nonsymbolic numerical discrimination could indicate a general ratio processing deficit. The finding of preserved nonsymbolic numerical magnitude discrimination and mental number line representations, with impaired symbolic number processing, in individuals with congenital amusia indicates that (a) pitch height and numerical magnitude processing may not share common neural representations, and (b) in addition to pitch processing, individuals with amusia may present a deficit in accessing nonsymbolic numerical representations from symbolic representations. The symbolic access deficit could reflect a widespread impairment in the establishment of cortico-cortical connections between association areas.

KEYWORDS:

• Congenital amusia
• Modularity
• Magnitude
• Music
• Number sense

Acknowledgements

The authors would like to thank members of the International Laboratory for Brain, Music and Sound Research/ Centre for Research on Brain, Language and Music (BRAMS/CRBLM) lab for their technical support and insightful comments.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

We are grateful for the technical support of BRAMS/CRBLM and the financial support from Natural Sciences and Engineering Research Council of Canada, the Canadian Institutes of Health Research and from the Canada Research Chairs. This research was also supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), [grant number 236604/2012-0], [grant number 308267/2014-1]; and Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) [grant number APQ-03642-12], [grant number APQ-02953-14].