Congenital amusics use a secondary pitch mechanism to identify lexical tones.

Oliver Bones,Patrick C.M. Wong

doi:10.1016/j.neuropsychologia.2017.08.004

Oliver Bones, Patrick C.M. Wong

Open Access

https://doi.org/10.1016/j.neuropsychologia.2017.08.004

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Abstract

Amusia is a pitch perception disorder associated with deficits in processing and production of both musical and lexical tones, which previous reports have suggested may be constrained to fine-grained pitch judgements. In the present study speakers of tone-languages, in which lexical tones are used to convey meaning, identified words present in chimera stimuli containing conflicting pitch-cues in the temporal fine-structure and temporal envelope, and which therefore conveyed two distinct utterances. Amusics were found to be more likely than controls to judge the word according to the envelope pitch-cues. This demonstrates that amusia is not associated with fine-grained pitch judgements alone, and is consistent with there being two distinct pitch mechanisms and with amusics having an atypical reliance on a secondary mechanism based upon envelope cues.

Highlights

Congenital amusia, commonly referred to as “tone deafness”, is a life-long disorder affecting processing and production of pitch
Consistent with results reported by Cousineau et al (2015), there was no evidence for a deficit in peripheral processing of temporal finestructure (TFS) in amusics
Consistent with Cousineau et al (2015), and with Liu et al (2014) who found no evidence for the representation of pitch information being degraded at the level of the auditory brainstem in amusics, no evidence was found in the present study for a deficit in the peripheral representation of TFS in amusics (Fig. 2A)

Summary

Introduction

Congenital amusia, commonly referred to as “tone deafness”, is a life-long disorder affecting processing and production of pitch. Sounds that produce pitch are mostly those that contain harmonic tones. The repetition rate of the F0, which is usually the same as the overall repetition rate of the complex tone (the temporal “envelope”), is the acoustic feature that is most related to pitch. If a single harmonic falls within the bandwidth of an auditory filter (see Glasberg and Moore, 1990) the harmonic is said to be “resolved”. When more than one harmonic falls within the bandwidth of an auditory filter they are said to be “unresolved” (above approximately the 8th to 10th harmonic; Bernstein and Oxenham, 2003; Plomp, 1964). Interactions between unresolved harmonics within the auditory filter produce complex AN firing patterns.

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