Does the late positive component reflect successful reading acquisition? A longitudinal ERP study

Abstract

Developmental dyslexia is a reading disorder that is associated with deficits in phonological processing, where the exact neural basis for those processing deficits remains unclear. In particular, disagreement exists whether degraded phonological representations or an impaired access to the phonological representations causes these deficits. To investigate this question and to trace changes in neurophysiology during the process of reading acquisition, we designed a longitudinal study with event related potentials (ERPs) in children between kindergarten and second grade. We used an explicit word processing task to elicit the late positive component (LPC), which has been shown to reflect phonological processing. A brain-wide analysis of the LPC with an electrode-wise application of mixed effects models showed significantly attenuated amplitudes in the left temporo-parietal region in dyslexic children. Since these differences were only present in the word and not in the picture (i.e. control) condition, the attenuated amplitudes might reflect impaired access to the phonological representations of words. This was further confirmed by the longitudinal development, which showed a rapid increase in amplitude at the beginning of reading instruction and a decrease with continuing automatization, possibly pointing to a progression from grapheme-phoneme parsing to whole word reading. Our longitudinal study provides the first evidence that it is possible to detect neurophysiological differences in the LPC between children with dyslexia and control children in both preliterate and very early stages of reading acquisition, providing new insights about the neurophysiological development and a potential marker of later reading problems.

Evidence from ERP and Eye Movements as Markers of Language Dysfunction in Dyslexia

“…These results suggest that the access to phonological representations of words may be impaired and/or that phonological representations may be underspecified [ 19 ] in dyslexic individuals. This hypothesis was later supported by Wachinger et al [ 31 ], who used a word processing task in a longitudinal study with German children between kindergarten and second grade. In this task, children were asked to read a word or look at a picture (control condition) and to decide whether it matched an acoustically presented word.…”

“…In addition, Hasko et al [ 19 ] surmised that LPC might reflect access to the phonological lexicon. With respect to dyslexia, reduced LPC amplitudes have been found in dyslexic adults [ 43 ], adolescents [ 30 ] and children [ 19 , 31 ]. For example, and as far as word recognition memory is concerned, Schulte-Körne et al [ 30 ] used a recognition paradigm with previously presented pseudowords and symbols in ten-year-old dyslexic children; in this task, participants had to study a list of pseudowords and symbol strings and then decide whether the presented stimulus had already been seen.…”

Brain dynamics of (a)typical reading development—a review of longitudinal studies

“…This seems to suggest delayed visual specialization maxima in dyslexic readers. In relation to phonological processing, another study 46 reported attenuated LPC amplitudes in children with dyslexia compared to typical readers. Interestingly, those effects were confined to word stimuli (in contrast to pictures) and temporo-parietal electrode sites.…”

“…Audiovisual integration was also examined in a longitudinal ERP study, which followed children across five time points from kindergarten to the end of the second grade 46 . The analysis focused on a late positive component (LPC) over the temporo-parietal scalp electrodes elicited by an explicit reading task, where congruent or incongruent audiovisual pairs were presented with either words or pictures.…”

Test-Retest Reliability of Event-Related Potentials Across Three Tasks

“…ERPs allow a very precise temporal tracking of the electrocortical brain activity, which in turn allows high sensitivity to the rapid information processing stream. Given their use to track cognitive processes in longitudinal (Fruehwirt et al, 2018; Wachinger et al, 2018) or clinical studies (Houston & Schlienz, 2018; Morand-Beaulieu et al, 2018), the test-retest reliability of ERPs must be established. Test-retest reliability refers to the consistency of a measure or an instrument over time.…”