Behavioral and neurological profiles in multiplex versus simplex dyslexia: a longitudinal approach

Dyslexia is one of the most common learning disorders, and despite the need for early interventions, the diagnosis can only be given after some years of reading failure. The past decade, efforts have been done to find behavioral and neurological measures that predict, prior to reading instruction onset, who will later on develop dyslexia. However, in these longitudinal studies, most kindergartners who eventually develop dyslexia concurrently have a family risk for dyslexia, i.e. having a first-degree relative with a dyslexia diagnosis (‘multiplex dyslexics’). Also in our own ongoing longitudinal study (G092012N), in which behavioral, MRI and EEG measures are yearly collected from kindergarten onwards, 17 dyslexic readers are multiplex and only 2 have no family risk (‘simplex dyslexics’). Given that multiplex and simplex dyslexic children might differ in their genetic basis, they might also differ in their behavioral and neurological profiles, hence resulting in other predictors and remedial needs. Therefore, the aim of this study is to extend our ongoing longitudinal study towards simplex dyslexics using the same measures prior and throughout reading development. The proposed study is timely and necessary since it will determine whether the traditionally known behavioral and neurological predictors of dyslexia are also applicable to simplex dyslexics. This will shed light on the multi-dimensionality of dyslexia and will lead to better adapted diagnostics and interventions.