The Long Road to Automation: Neurocognitive Development of Letter–Speech Sound Processing

Abstract

In transparent alphabetic languages, the expected standard for complete acquisition of letter-speech sound associations is within one year of reading instruction. The neural mechanisms underlying the acquisition of letter-speech sound associations have, however, hardly been investigated. The present article describes an ERP study with beginner and advanced readers in which the influence of letters on speech sound processing is investigated by comparing the MMN to speech sounds presented in isolation with the MMN to speech sounds accompanied by letters. Furthermore, SOA between letter and speech sound presentation was manipulated in order to investigate the development of the temporal window of integration for letter-speech sound processing. Beginner readers, despite one year of reading instruction, showed no early letter-speech sound integration, that is, no influence of the letter on the evocation of the MMN to the speech sound. Only later in the difference wave, at 650 msec, was an influence of the letter on speech sound processing revealed. Advanced readers, with 4 years of reading instruction, showed early and automatic letter-speech sound processing as revealed by an enhancement of the MMN amplitude, however, at a different temporal window of integration in comparison with experienced adult readers. The present results indicate a transition from mere association in beginner readers to more automatic, but still not "adult-like," integration in advanced readers. In contrast to general assumptions, the present study provides evidence for an extended development of letter-speech sound integration.

Event-related potentials to tones show differences between children with multiple risk factors for dyslexia and control children before the onset of formal reading instruction

“…It has been suggested that the LDN response reflects processes of letter-speech sound integration, attention, long-term memory transfer, or further cognitive processing of the sound change (Ceponiene et al, 2004;Cheour et al, 2001;Froyen et al, 2009;Shestakova et al, 2003;Zachau et al, 2005). In the present study, no letter-speech sound integration was possible in the experimental paradigm, and the sine-wave tones would be unlikely to activate long-term memory representations or to require the storage of complex rules.…”

The COGs (context, object, and goals) in multisensory processing

“…As discussed, prolonged experience with the perceptual processing of particular multisensory pairings might result in thedetectionof their presence relatively independently of one's goals (e.g. Froyen et al 2009). Notably, the benefits of long-term experiences might generalise to multi-stimulus settings, with the multisensory congruence across some types of object features being detected independently of the level of competition within the relevant sense.…”

“…Other studies are inconsistent with these findings. While early-latency, automatic brain processes (mismatch negativity, MMN) are modulated by the detection of script congruence even within task-irrelevant AV stimuli, this ability develops only after years of reading instruction (Froyen et al 2009; cf. the early onset of speech congruence detection; Soto-Faraco et al 2012).…”

“…experience) seems to determine the presence of multisensory processing in some cases (e.g. observers' reading proficiency, Froyen et al 2009), but not in others (e.g. temporal coincidence of multisensory stimuli is detected early in life, Lewkowicz 2014).…”

“…Tuomainen et al 2005; Wallace 2013) and long-term experiences (e.g. Froyen et al 2009;Matusz et al 2015b;Ten Oever et al 2013) are vital to the presence and the effects of many multisensory processes that are dependent on object matching, sensitivity to both multisensory simultaneity and speech congruency seems to develop early in life (Soto-Faraco et al 2012;Lewkowicz et al 2014). The full extent to which dependence of a multisensory process on one form of top-down control indeed impacts dependenceon other types of control is further complicated by the likely contingence of top-down expectations and object-matching processes on goalbased control, especially during development (e.g.…”