Slide Slam K14
Electrophysiological responses to words with a frequently recurring phoneme in adults with a history of developmental dyslexia
Johanna Funk1, Christina Kauschke1, Ulrike Domahs1; 1Philipps University Marburg
In auditory word recognition, the sound structure comprising a string of phonemes needs to be mapped onto meaningful representations in the mental lexicon. This mapping may be impeded as a result of phonological deficits that are typical for individuals with developmental dyslexia (DD) and are observable in deviating electrophysiological responses to phonological processing and priming effects during word recognition (Desroches et al., 2013). In the present study, we aimed at enhancing our knowledge about phonological priming effects. We investigated whether the frequent presentation of a certain phoneme may enhance its expectation for a longer period of time and modify the processing of later encountered words. To our knowledge, this is the first study examining effects of sensitization (as a form of priming) on a phonological target structure, as it is already used in intervention for children with speech-sound-disorders, who are at risk for DD (Bruinsma et al., 2020; Kauschke & Siegmüller, 2019). In the present study, event-related potentials were used to investigate effects of a frequently recurring phoneme (termed phonological stimulation) on the processing of German (pseudo)words with this phoneme as onset. The effect of phonological stimulation was investigated in typically reading adults (n = 19) and adults with a self-reported history of DD (n = 13) performing an auditory Lexical Decision Task (LDT) after listening to a short story that was designed to present the phoneme /g/ with a high frequency. In the LDT, it was examined whether the frequent presentation of /g/ leads to a sensitization for this specific phoneme reflected in different electrophysiological responses to (pseudo)words with /g/ as word onset compared to (pseudo)words with a control phoneme (/b/) and further, whether responses to the two sets of (pseudo-)words differ between the two groups of participants. ERP results analyzed with linear mixed-effects models revealed a negativity effect for the frequently presented phoneme in the pre-lexical N100 time-window in typical readers, but not in adults with a history of DD. These findings suggest a reduced sensitivity to phonological information in word onsets in individuals with DD during early processing phases. However, sensitization related modulations of ERPs for this group were observable in the time-windows associated with the N400 and Late Positive Component, indicating an effect of sensitization in later lexical processing stages of word recognition. Furthermore, the typical enhanced N400 effect for pseudowords in comparison to words occurred in the DD-group only for /g/-words, but not for /b/-words. Overall, the findings of the present study provide evidence that phonological stimulation influences the activation of a certain cohort and affects different processing stages of word recognition in individuals with a history of DD compared to typically reading adults. The results do not only suggest that individuals with phonological impairments may benefit from the repeated presentation of a phonological structure, but also that phonological sensitization modulates pre-lexical and lexical processing steps. This points towards implications for interventions involving focused stimulation of specific phonemes in speech and language therapy.