The use of rat models to investigate the role of dyslexia genes in the phenotype is only the first step. These models are only truly helpful if they tell us something useful and relevant about the way this disorder presents in humans. This branch of my program tests how translational these models are by looking in humans for the neural and behavioral profiles discovered in rats.
My previous work in rats and recent work in the human auditory brainstem (Hornickel & Kraus 2013) suggests that increased neural variability may be present in children with dyslexia, but there is significant debate in the field regarding the prevalence of auditory temporal processing deficits. Our recent study tested the hypothesis that neural inconsistency was present in cortex in a percentage of children with dyslexia. Children with dyslexia and typically developing controls were assessed for reading, oral language, and nonverbal IQ before participating in a behavioral speech discrimination experiment and a passive neural imaging session using magnetoencephalography (MEG). In this session, children listened to speech sounds and tones and looked at lowercase letters and nonsense objects.
We observed significantly higher inconsistency to auditory stimuli in left auditory cortex of 47% of children with dyslexia. Interestingly, the degree of neural inconsistency was related to timed word reading scores and children with higher variance to speech sounds also had higher variance to other stimuli, such as letters and unnameable objects. My collaborators are also currently testing saliva samples from these children to determine whether variants in KIAA0319 are present in those with inconsistent neural responses.
- TM Centanni, D Pantazis, L Denna, JDE Gabrieli, TP Hogan (2015) Variability in the auditory-evoked neural response as a potential mechanism for dyslexia, Society for Neuroscience, Chicago
- TM Centanni, D Pantazis, JDE Gabrieli, TP Hogan. Inconsistent neural responses in cortex: a potential neural mechanism for heterogeneity in dyslexia. Manuscript in preparation
Additional recent work suggests that some children with dyslexia may have reduced volume in the arcuate fasciculus; a white matter tract connecting two important areas of the language network (Saygin et al., 2011). Several researchers have suggested that this could contribute to the rapid naming deficits seen in children with dyslexia and is reminiscent of the profile discovered in the Dcdc2 RNAi rats (Learn more...). The goal of this ongoing study is to determine whether the children with dyslexia who struggle with rapid naming and fluency are also the same children with variants in DCDC2. As part of this study, we are also testing to see if auditory processing difficulties occur together with rapid naming deficits or if this is a unique neural and behavioral subtype.