Increasing evidence exists that poor speech perception abilities precede the phonological deficits typically observed in dyslexia, a developmental disorder in learning to read. Impaired processing of dynamic features of speech, such as slow amplitude fluctuations and transient acoustic cues, disrupts effortless tracking of the speech envelope and constrains the development of adequate phonological skills. In this study, a speech envelope enhancement (EE) strategy was implemented to reduce speech perception deficits by students with dyslexia. The EE emphasizes onset cues and reinforces the temporal structure of the speech envelope specifically.
Speech perception was assessed in 42 students with and without dyslexia using a sentence repetition task in a speech-weighted background noise. Both natural and vocoded speech were used to assess the contribution of the temporal envelope on the speech perception deficit. Their envelope-enhanced counterparts were added to each baseline condition to administer the effect of the EE algorithm. In addition to speech-in-noise perception, general cognitive abilities were assessed.
Results demonstrated that students with dyslexia not only benefit from EE but benefit more from it than typical readers. Hence, EE completely normalized speech reception thresholds for students with dyslexia under adverse listening conditions. In addition, a correlation between speech perception deficits and phonological processing was found for students with dyslexia, further supporting the relation between speech perception abilities and reading skills. Similar results and relations were found for conditions with natural and vocoded speech, providing evidence that speech perception deficits in dyslexia stem from difficulties in processing the temporal envelope.
Using speech EE, speech perception skills in students with dyslexia were improved passively and instantaneously, without requiring any explicit learning. In addition, the observed positive relationship between speech processing and advanced phonological skills opens new avenues for specific intervention strategies that directly target the potential core deficit in dyslexia.
1Department of Neurosciences, Research Group Experimental ORL, KU Leuven—University of Leuven, Leuven, Belgium
2Faculty of Psychology and Education Sciences, Parenting and Special Education Research Unit, KU Leuven—University of Leuven, Leuven, Belgium.
Received August 24, 2018; accepted December 18, 2018.
This work was funded by grant [G.0A91.15N] from the Research Foundation—Flanders (FWO).
There are no conflicts of interest to disclose.
Portions of this article were presented at the The International Hearing Aid Research Conference, Lake Tahoe, California, United States (August 15 to 18, 2018), and at the Audiological Research Centers in Europe (ARCHES) Conference, Nottingham, UK (November 12 to 13, 2018).
Regarding author contributions, T.V.H. and J.W. designed the experiments. T.V.H. and P.G. designed the cognitive tasks and recruited the subjects. T.V.H. performed the research, analyzed the data, and wrote the manuscript. A.M.T. and J.W. worked out and optimized the signal processing. P.G. and J.W. supervised the research. All authors edited the manuscript.
Address for correspondence: Tilde Van Hirtum, O&N2, Herestraat 49—Box 721, B-3000 Leuven, Belgium. E-mail: email@example.com
Online date: March 05, 2019