Neuromagnetic speech discrimination responses are associated with reading-related skills in dyslexic and typical readers

A Thiede; L Parkkonen; P Virtala; M Laasonen; J P Mäkelä; T Kujala

doi:10.1016/j.heliyon.2020.e04619

Neuromagnetic speech discrimination responses are associated with reading-related skills in dyslexic and typical readers

Heliyon. 2020 Aug 25;6(8):e04619. doi: 10.1016/j.heliyon.2020.e04619. eCollection 2020 Aug.

Authors

A Thiede¹, L Parkkonen^{2

3}, P Virtala¹, M Laasonen^{4

5}, J P Mäkelä⁶, T Kujala¹

Affiliations

¹ Cognitive Brain Research Unit, Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Finland.
² Department of Neuroscience and Biomedical Engineering, School of Science, Aalto University, Finland.
³ Aalto Neuroimaging, Aalto University, Finland.
⁴ Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Finland.
⁵ Department of Phoniatrics, Helsinki University Hospital, Finland.
⁶ BioMag Laboratory, HUS Medical Imaging Center, Helsinki University Central Hospital, Finland.

Abstract

Poor neural speech discrimination has been connected to dyslexia, and may represent phonological processing deficits that are hypothesized to be the main cause for reading impairments. Thus far, neural speech discrimination impairments have rarely been investigated in adult dyslexics, and even less by examining sources of neuromagnetic responses. We compared neuromagnetic speech discrimination in dyslexic and typical readers with mismatch fields (MMF) and determined the associations between MMFs and reading-related skills. We expected weak and atypically lateralized MMFs in dyslexic readers, and positive associations between reading-related skills and MMF strength. MMFs were recorded to a repeating pseudoword /ta-ta/ with occasional changes in vowel identity, duration, or syllable frequency from 43 adults, 21 with confirmed dyslexia. Phonetic (vowel and duration) changes elicited left-lateralized MMFs in the auditory cortices. Contrary to our hypothesis, MMF source strengths or lateralization did not differ between groups. However, better verbal working memory was associated with stronger left-hemispheric MMFs to duration changes across groups, and better reading was associated with stronger right-hemispheric late MMFs across speech-sound changes in dyslexic readers. This suggests a link between neural speech processing and reading-related skills, in line with previous work. Furthermore, our findings suggest a right-hemispheric compensatory mechanism for language processing in dyslexia. The results obtained promote the use of MMFs in investigating reading-related brain processes.

Keywords: Applied linguistics; Behavioral neuroscience; Clinical psychology; Cognitive neuroscience; Cognitive psychology; Dyslexia; Magnetoencephalography (MEG); Mismatch field (MMF); Reading skills; Speech processing; Verbal working memory.