Abstract
Written language has become indispensable for communication in our society. Reading difficulties therefore pose a severe obstacle to the active involvement as a citizen. Consequently, developmental dyslexia (DYS) can lead to poor educational outcomes, diminished future professional opportunities, and compromised mental health. Although a diverse set of models for the etiology and underlying (neural) deficits of DYS have been put forward and multiple neural processes may in fact be affected by DYS, automatic visual word recognition and audiovisual (AV) integration are two skills that are thought to be foundational for reading and are often proposed to be altered in DYS. However, few studies have investigated the temporal profile and level of automatic visual processing of orthography in the brain across a range of reading proficiencies in children. Furthermore, it remains understudied how children with varying reading abilities use prior auditory cues to help them process visual information. Hence, in this dissertation project, we investigated the influence of reading skills on automatic visual processing and audiovisual integration in beginning readers in two EEG studies.
Previous studies have suggested that visual neural print sensitivity follows an extended development in children and is reduced in children with reading impairments. In our first study, we investigated whether and to what degree beginning readers demonstrate print sensitivity and familiarity and whether there are differences in neural processing between children with typical (TR) and poor reading skills (PR). We recorded brain responses to a rapid sequence of visual stimuli where most stimuli belonged to the same category (base) and a stimulus of a deviating category (oddball) was shown less frequently. A differential brain response to the infrequent deviant stimulus signifies automatic detection of the visual change and differentiation between the oddball and the base. To test the level of sensitivity to print, we contrasted false font (FF) and consonant string (CS) oddballs against word (W) bases. Specifically, FF in W assessed coarse print sensitivity, while CS in W evaluated fine print sensitivity. Additionally, to determine the automatic familiarity with orthographic regularity, we compared W, pseudoword (PW), and CS oddballs inserted into an FF sequence. Our findings indicated the presence of coarse but not fine print sensitivity responses in both reading groups. For orthographic regularity, we found a stepwise difference in activation to the conditions, with stronger activations to oddballs containing more familiar/regular letter combinations (W) than those with less regular letter combinations (CS). This effect was more pronounced and exhibited greater left-lateralization in TR than PR. In contrast, PR displayed a similar activation pattern in the right hemisphere. These results align with prior research, suggesting that although both PR and TR exhibit early coarse sensitivity to print, sublexical processing is emerging in TR but altered in PR.
In the second study, we were interested in the influence of reading skills on AV integration depending on orthography (W versus Obj) and lexicality (W versus PW). As a measure of AV integration, we compared electrophysiological responses to incongruent and congruent AV stimulus pairs. Behavioral findings indicated greater difficulties in perceiving or resolving AV conflicts in children with poorer reading skills specifically for orthographic conditions. Moreover, on a neural level, we observed faster integration of non-orthographic than orthographic AV pairs on all reading levels, but more pronounced orthographic integration processing for children with higher reading skills. These results suggest a domain-specific alteration in the visual matching of orthographic conditions with an auditory prime in children with poorer reading abilities.
In this work, we gained new and more resolved knowledge about the level of automatic visual print and familiarity processing and AV integration in Swiss-German 2nd-3rd grade children with different reading abilities. Our results support and expand upon the idea that children with typical reading abilities undergo extended developmental refinement in neural orthographic processing and AV congruency priming. Conversely, children with reading impairments experience delayed or altered development in print-related behavioral and neural processes. These findings contribute to our understanding of the processes underlying reading and deficits thereof in children with DYS. Several possible approaches to refine future studies are discussed, including adopting a longitudinal design, systematically comparing various experimental parameters, accounting for individual variability or subgroup differences, and implementing innovative analysis methods. Lastly, we emphasize the need to effectively communicate and translate research findings
Lutz, Christina