Development of temporal auditory processing in childhood: Changes in efficiency rather than temporal-modulation selectivity

Abstract

The ability to detect amplitude modulation (AM) is essential to distinguish the spectro-temporal features of speech from those of a competing masker. Previous work shows that AM sensitivity improves until 10 years of age. This may relate to the development of sensory factors (tuning of AM filters, susceptibility to AM masking) or to changes in processing efficiency (reduction in internal noise, optimization of decision strategies). To disentangle these hypotheses, three groups of children (5-11 years) and one of young adults completed psychophysical tasks measuring thresholds for detecting sinusoidal AM (with a rate of 4, 8, or 32 Hz) applied to carriers whose inherent modulations exerted different amounts of AM masking. Results showed that between 5 and 11 years, AM detection thresholds improved and that susceptibility to AM masking slightly increased. However, the effects of AM rate and carrier were not associated with age, suggesting that sensory factors are mature by 5 years. Subsequent modelling indicated that reducing internal noise by a factor 10 accounted for the observed developmental trends. Finally, children's consonant identification thresholds in noise related to some extent to AM sensitivity. Increased efficiency in AM detection may support better use of temporal information in speech during childhood.

Development of Binaural Sensitivity: Eye Gaze as a Measure of Real-time Processing

“…In auditory tasks that involve signal detection in noise, internal noise in the form of variability in the neural representation of the auditory input has been attributed to individual differences in behavioral outcomes (Buss et al, 2006 ). Until late adolescence, children demonstrate elevated internal noise as compared to adults in detecting tone in noise (Buss et al, 2006 ) and amplitude modulation (Cabrera et al, 2019 ). In tasks that involve cross-frequency masking, immature selective attention is also found to be responsible for poorer performances in children as compared to adults (Lutfi et al, 2003 ; Leibold and Neff, 2007 , 2011 ; Jones et al, 2015 ).…”

Temporal integration for amplitude modulation in childhood: Interaction between internal noise and memory factors

“…This experiment was part of a larger project on temporal processing capacity in childhood assessing modulation masking as well (see Cabrera et al, 2019). Children completed the whole experiment within 4 sessions of 20 min over a 2-week period and adults in one session of 1.5 hr.…”

“…Four adults were not included in the final sample because of missing data due to experimental errors. Furthermore, a total of 10 outliers were flagged and their data were not included in the analyses (see Cabrera et al, 2019).…”

“…More precisely, Model A uses the SD of the internal noise that maximized the model's "goodness-of-fit" at the 8 Hz AM rate. This was achieved by minimizing the model's mean absolute error, evaluated as the average absolute value of the difference between simulated AMDTs and "real" AMDTs averaged across participants for each age group in Cabrera et al (2019). The SD of the internal noise is set to 2 x 10 -4 for adults, 5 x 10 -4 for 10-11-year-olds, 1 x 10 -3 , for 7-8-year-olds, and 2 x 10 -3 m.u.…”

“…However, the overall effect of age on detection thresholds in the masked conditions indicates reduced efficiency in AM processing in childhood. Cabrera et al (2019) explored further the development of AM masking in childhood and the role of "processing efficiency", the ability to make optimal use of the available temporalmodulation information at the output of modulation filters in the case of AM perception. It was hypothesized that poor AM detection thresholds in childhood may relate to higher levels of internal noise (neural variability at each level of the auditory system) and/or the use of sub-optimal decision strategies.…”