Identification of neurobiological causes in children with isolated reading / spelling deficits

Theoretical Background: Dyslexia is one of the most common developmental disorders. During the past decades numerous investigations of the cognitive and neurobiological factors underlying reading and spelling deficits have improved our understanding of literacy difficulties. The majority of these studies were based on the assumption that deficits in reading and deficits in spelling comprise one and the same disorder. However, recent research provides evidence that deficits in reading (fluency) can occur in the absence of deficits in spelling and vice versa, constituting a double-dissociation. Furthermore, there is evidence that reading and spelling deficits may be associated with differential cognitive profiles and may have different aetiologies. Aims: This research project aims to further specify the dissociations between reading and spelling deficits based on detailed analyses of word recognition processes. Different methods, including eye-tracking, ERP and fMRI will be applied in order to investigate cognitive and neurobiological correlates of word recognition and how they can explain the conditions under which deficits in reading and deficits in spelling occur in isolation. The project will provide a comprehensive understanding of the mechanisms underlying isolated reading and isolated spelling deficits. The inclusion of different levels of analysis (behavioural, cognitive and brain level) will help to further specify neuro-cognitive models of reading and spelling development. The results are equally relevant for intervention as findings can provide the basis for training programmes that are specifically tailored towards individual problems. Method: The grant proposal is conceptualised as a bilateral project (DACH project) in order to benefit from synergy effects. The involvement of two different research centres is seminal to the success of the project; it ensures reasonable sample sizes and enables analyses on three different levels (behaviour, cognition, and brain) by combining different areas of expertise. The two neurobiological methods (fMRI and ERP) will be divided between research sites according to their expertise, so that the fMRI data are collected based on the sample in Graz and the ERP data based on the sample in Munich. The behavioural and cognitive measures (including eye-tracking) will be assessed at both research sites. This procedure allows associating the behavioural and cognitive skills with the neurobiological correlates of the specific deficit groups. In order to assess the cognitive and neurobiological profiles associated with isolated and combined rd th reading and/or spelling problems four specifically selected groups of 3 /4 Graders will be recruited based on their performance in classroom tests of reading and spelling (isolated reading disorder, isolated spelling disorder, combined reading and spelling disorder, and controls). The carefully selected groups (N=80 per research site) will participate in drei individual assessments to examine the cognitive profiles and neurobiological correlates that are associated with isolated and combined deficits. The focus will be on the investigation of lexical and sublexical processes in word recognition and on cognitive skills associated with word recognition processes.

The project set out to understand why reading and spelling problems can dissociate even though development of both literacy skills is based on similar processes, such as phonological skills, letter-sound knowledge, sublexical processes (decoding/recoding), and lexical processes (building-up word specific representations). We aimed to identify the neuro- cognitive profiles and deficits in sublexical and lexical word processing that are specifically related to problems in reading fluency versus problems in spelling. Findings show that problems in reading fluency and problems in spelling are associated with distinguishable deficits in written word processing. It is often assumed that dysfluent reading results from overreliance on sublexical decoding (i.e., sounding out letter-by-letter). The current evidence, however, clearly shows that this assumption is wrong. Instead, findings suggest that poor readers do apply lexical strategies of whole word recognition, but are extremely slow in accessing written word representations. Results from cognitive and neurophysiological paradigms showed that dysfluent reading is best explained by deficits in efficient word processing as well as visual-verbal access. Problems in spelling are caused by deficits in building-up word specific representations and storing them in long-term memory. Underspecified representations are sufficient for word recognition during reading, but not for spelling a word correctly. This explains why children can be poor spellers although their reading skills are intact. The exact causal mechanisms underlying problems in building up word specific representations are not yet fully identified. Based on previous research and the current findings, identified risk factors are poor phonological skills (i.e. in preschool and early school years) and deficits in orienting attention. Additional risk factors which were not tested in the current project, such as morphological awareness, may also play a role. Our results have important practical implications: During the diagnostic process it is important to differentiate between isolated reading disorder, isolated spelling disorder, and combined reading and spelling disorder as they are related to different cognitive deficit profiles. Interventions need to be tailored towards the individual deficit profile. In recent years, many training programmes focus on phonological awareness. However, such programmes are not suitable for children with isolated reading problems as their phonological skills are unaffected. Instead training programmes for this group should to address their problems in automatizing letter-sound associations as well as efficiency of visual-verbal access and word processing.