How Do Adults with Dyslexia Recognize Spoken Words? Evidence from Behavioral and EEG Data

Abstract

Purpose: In speech processing, the impacts of persistent phonological deficits in dyslexic readers (DYS) are typically reported in meta-phonological, verbal short-term memory, and challenging speech identification tasks. Here, we examined whether such deficits also generalize to a less demanding speech recognition situation.Method: Adults with and without dyslexia performed an auditory lexical decision task.Performance and event-related potentials (ERP) were recorded.Results: Reaction times showed a lexicality effect in both groups, with overall slower responses in DYS. ERP data distinguished the two populations at the lexico-semantic stage of word recognition. The early phase of N400 showed an unusual amplitude enhancement for words compared to pseudowords in DYS. N400 amplitude in skilled readers dropped in the later phase of word recognition, leading to the typical lexicality effect, but this activity was sustained in DYS. Finally, skilled readers and DYS showed no difference in pseudoword processing.Conclusions: The combination of the early enhancement and sustained N400 responses to words observed in DYS and the absence of a group effect during pseudoword processing indicate an over-reliance on semantic representations when DYS recognize spoken words.Further research is needed to determine whether this reflects a compensation mechanism or a residual impact of phonological deficits.

Overt Word Reading and Visual Object Naming in Adults with Dyslexia: Electroencephalography Study in Transparent Orthography

“…Also, according to previously reported findings, adult PDs might have persistent phonological processing difficulties during reading and exhibit a lower score in rapid naming, working memory, and visual-attention [84,[124][125][126]. Contrary to PDs, HCs use more efficiently a direct lexical route in decoding familiar words during word reading, while adult PDs rely on a nonlexical route and require extra time for decoding, similar to the decoding process seen in dyslexic children [126] as well in adult PDs [127][128][129]. However, several ERP studies conducted on non-transparent languages using covert design (delayed phonological task, auditory lexical decision task) failed to find differences in the pre-lexical processing stage in adult PDs compared to controls [127,128].…”

“…Contrary to PDs, HCs use more efficiently a direct lexical route in decoding familiar words during word reading, while adult PDs rely on a nonlexical route and require extra time for decoding, similar to the decoding process seen in dyslexic children [126] as well in adult PDs [127][128][129]. However, several ERP studies conducted on non-transparent languages using covert design (delayed phonological task, auditory lexical decision task) failed to find differences in the pre-lexical processing stage in adult PDs compared to controls [127,128]. The differences in adult PDs compared to HCs were reported in the post-lexical stage after the first 300 ms in the left hemisphere with reduced ERP amplitudes to words compared to pseudo words during the delayed phonological task and auditory lexical decision task [127,128].…”

“…However, several ERP studies conducted on non-transparent languages using covert design (delayed phonological task, auditory lexical decision task) failed to find differences in the pre-lexical processing stage in adult PDs compared to controls [127,128]. The differences in adult PDs compared to HCs were reported in the post-lexical stage after the first 300 ms in the left hemisphere with reduced ERP amplitudes to words compared to pseudo words during the delayed phonological task and auditory lexical decision task [127,128]. Contrary to these findings, Mahe et al [56] failed to find differences in the pre-lexical stage of processing during lexical decision task in adult PDs compared to HCs on non-transparent language by using lexical decision task, assuming that overt (reading aloud) task might be more suitable to investigate phonological processing compared to lexical decision task.…”