Rapid changes in brain activity during learning of grapheme-phoneme associations in adults

Abstract

Learning to associate written letters with speech sounds is crucial for the initial phase of acquiring reading skills. However, little is known about the cortical reorganization for supporting letter-speech sound learning, particularly the brain dynamics during the learning of grapheme-phoneme associations.In the present study, we trained 30 Finnish participants (mean age: 24.33 years, SD: 3.50 years) to associate novel foreign letters with familiar Finnish speech sounds on two consecutive days (first day ~ 50 minutes; second day ~ 25 minutes), while neural activity was measured using magnetoencephalography (MEG). Two sets of audiovisual stimuli were used for the training in which the grapheme-phoneme association in one set (Learnable) could be learned based on the different learning cues provided, but not in the other set (Control). The learning progress was tracked at a trialby-trial basis and used to segment different learning stages for the MEG source analysis. The learningrelated changes were examined by comparing the brain responses to Learnable and Control uni/multisensory stimuli, as well as the brain responses to learning cues at different learning stages over the two days. We found dynamic changes in brain responses related to multi-sensory processing when grapheme-phoneme associations were learned. Further, changes were observed in the brain responses to the novel letters during the learning process. We also found that some of these learning effects were observed only after memory consolidation the following day. Overall, the learning process modulated the activity in a large network of brain regions, including the superior temporal cortex and the dorsal (parietal) pathway. Most interestingly, middle-and inferior-temporal regions were engaged during multi-sensory memory encoding after the cross-modal relationship was extracted from the learning cues.Our findings highlight the brain dynamics and plasticity related to the learning of letter-speech sound associations and provide a more refined model of grapheme-phoneme learning in reading acquisition.

The different brain areas occupied for integrating information of hierarchical linguistic units: a study based on EEG and TMS

“…Specifically, in the audio-visual condition as compared to the unimodal condition, the processing of words led to more significantly stronger activation in the parietal areas. This is in line with a previous MEG study in Finnish school children that emphasizes the crucial role of the parietaltemporal cortex in the early phase of reading [9]. The parietal areas may be involved in early audio-visual integration [12,42,43].…”

“…An increasing body of studies has explored the mechanisms underlying audiovisual integration of letters and speech sounds [7][8][9] and consistently demonstrated the superiority of audio-visual integration over processing letters and speech sounds separate [10,11]. For example, a magnetoencephalography (MEG) study showed enhanced brain activity predominantly in the right temporal-occipital-parietal junction and the left and right superior temporal sulci for audio-visual integration of phonemes and graphemes [12].…”

A Spatiotemporal Map of Reading Aloud

“…IPS has previously been implicated in the grapheme-phoneme conversion process (Dehaene-Lambertz et al, 2018;Xu et al, 2020). Given that IPS shows both word frequency and lexicality sensitivity, its role in sub-lexical processing might appear to be questionable.…”

The visual‐attention span deficit in developmental dyslexia: Review of evidence for a visual‐attention‐based deficit

“…Language abilities are associated with the perisylvian brain network within the left hemisphere, including inferior frontal areas, the superior temporal cortex and the inferior parietal lobule (Price, 2012). Reduced activation of these brain regions has been related to phonological and visual‐verbal mapping deficits in developmental dyslexia (Blomert, 2011; Démonet, Taylor, & Chaix, 2004; Richlan, 2012, 2019; Xu, Kolozsvari, Oostenveld, & Hämäläinen, 2020). Visuo‐spatial attention has instead been related to posterior brain areas bilaterally, including the temporal parietal junction, the superior parietal lobule (SPL) and the frontal eye fields (Behrmann, Geng, & Shomstein, 2004; Carrasco, 2011).…”