Impaired encoding of rapid pitch information underlies perception and memory deficits in congenital amusia

Abstract

Recent theories suggest that the basis of neurodevelopmental auditory disorders such as dyslexia or specific language impairment might be a low-level sensory dysfunction. In the present study we test this hypothesis in congenital amusia, a neurodevelopmental disorder characterized by severe deficits in the processing of pitch-based material. We manipulated the temporal characteristics of auditory stimuli and investigated the influence of the time given to encode pitch information on participants’ performance in discrimination and short-term memory. Our results show that amusics’ performance in such tasks scales with the duration available to encode acoustic information. This suggests that in auditory neuro-developmental disorders, abnormalities in early steps of the auditory processing can underlie the high-level deficits (here musical disabilities). Observing that the slowing down of temporal dynamics improves amusics’ pitch abilities allows considering this approach as a potential tool for remediation in developmental auditory disorders.

Auditory deficits in amusia extend beyond poor pitch perception

“…This indicates that amusics have an underlying pitch and frequency coding deficit that cannot be explained entirely by memory load or segmentation, but this effect is much smaller than observed in more traditional frequency discrimination paradigms (e.g., experiment 1). Furthermore, our results could suggest amusia is not a problem with processing rapid, fine-grained pitch information, as proposed by Albouy et al (2016). This is because amusics were equally impaired at processing slow-rate vs. fast-rate FM.…”

“…This is because amusics were equally impaired at processing slow-rate vs. fast-rate FM. Albouy et al (2016) found that amusics were impaired at detecting pitch changes in short (100 ms) but not long (350 ms) duration tones relative to controls. While the present study only used long duration FM tones (1500 ms), potentially limiting the comparison to Albouy et al (2016), a given cycle of FM is much longer for slow-rate FM (250 ms when f m = 4 Hz) compared to fast-rate FM (50 ms when f m = 20 Hz).…”

“…Albouy et al (2016) found that amusics were impaired at detecting pitch changes in short (100 ms) but not long (350 ms) duration tones relative to controls. While the present study only used long duration FM tones (1500 ms), potentially limiting the comparison to Albouy et al (2016), a given cycle of FM is much longer for slow-rate FM (250 ms when f m = 4 Hz) compared to fast-rate FM (50 ms when f m = 20 Hz). Findings from Albouy et al (2016) can possibly be attributed to using constant stimuli methods, where all participants were presented with the same Δ f (1 or 2 semitones), leading to near ceiling pitch-change detection performance in the controls for the longer-duration tones.…”

“…This outcome supports the hypothesis that amusics have an underlying deficit in fine-grained frequency discrimination that extends beyond problems with memory or segmentation. However, the fact that the performance of amusics was equally degraded at FM rates of both 4 and 20 Hz is not, at face value, consistent with the suggestion that amusia results in particularly poor processing of rapid fine-grained pitch information (Albouy et al, 2016). If this were the case, one might expect an interaction between group and modulation rate, with poorer thresholds in amusics at faster modulation rates.…”

“…It is possible, however, that the task design in the present study is too different from Albouy et al to expect generalization, perhaps because the tones here are much longer and the changes over time are continuous, rather than discrete. Either poor rapid pitch encoding in amusics only applies to steady tones, and not FM, or the interaction Albouy et al (2016) observed between group and tone duration reflected ceiling effects in the control group at the longer durations.…”