Probability learning and feedback processing in dyslexia: A performance and heart rate analysis.

Recent studies suggest that individuals with dyslexia may be impaired in probability learning and performance monitoring. These observations are consistent with findings indicating atypical neural activations in frontostriatal circuits in the brain, which are important for associative learning. The current study further examined probability learning and performance monitoring in adult individuals with dyslexia (n = 23) and typical readers (n = 31) using two varieties of a typical probabilistic learning task. In addition to performance measures, we measured heart rate, focusing on cardiac slowing with negative feedback as a manifestation of the automatic performance monitoring system. One task required participants to learn associations between artificial script and speech sounds and the other task required them to learn associations between geometric forms and bird sounds. Corrective feedback (informative or random) was provided in both tasks. Performance results indicated that individuals with dyslexia and typical readers learned the associations equally well in contrast to expectations. We found the typical cardiac response associated with feedback processing consisting of a heart rate slowing with the presentation of the feedback and a return to baseline thereafter. Interestingly, the heart rate slowing associated with feedback was less pronounced and the return to baseline was delayed in individuals with dyslexia relative to typical readers. These findings were interpreted in relation to current theorizing of performance monitoring linking the salience network in the brain to autonomic functioning.

Graph analysis of EEG resting state functional networks in dyslexic readers.

OBJECTIVE: Neuroimaging research suggested a mixed pattern of functional connectivity abnormalities in developmental dyslexia. We examined differences in the topological properties of functional networks between 29 dyslexics and 15 typically reading controls in 3rd grade using graph analysis. Graph metrics characterize brain networks in terms of integration and segregation. METHOD: We used EEG resting-state data and calculated weighted connectivity matrices for multiple frequency bands using the phase lag index (PLI). From the connectivity matrices we derived minimum spanning tree (MST) graphs representing the sub-networks with maximum connectivity. Statistical analyses were performed on graph-derived metrics as well as on the averaged PLI connectivity values. RESULTS: We found group differences in the theta band for two graph metrics suggesting reduced network integration and communication between network nodes in dyslexics compared to controls. CONCLUSION: Collectively, our findings point to a less efficient network configuration in dyslexics relative to the more proficient configuration in the control group. SIGNIFICANCE: Graph metrics relate to the intrinsic organization of functional brain networks. These metrics provide additional insights on the cognitive deficits underlying dyslexia and, thus, may advance our knowledge on reading development. Our findings add to the growing body literature suggesting compromised networks rather than specific dysfunctional brain regions in dyslexia.

Responsivity to dyslexia training indexed by the N170 amplitude of the brain potential elicited by word reading.

The present study examined training effects in dyslexic children on reading fluency and the amplitude of N170, a negative brain-potential component elicited by letter and symbol strings. A group of 18 children with dyslexia in 3rd grade (9.05±0.46years old) was tested before and after following a letter-speech sound mapping training. A group of 20 third-grade typical readers (8.78±0.35years old) performed a single time on the same brain potential task. The training was differentially effective in speeding up reading fluency in the dyslexic children. In some children, training had a beneficial effect on reading fluency ('improvers') while a training effect was absent in others ('non-improvers'). Improvers at pre-training showed larger N170 amplitude to words compared to non-improvers. N170 amplitude decreased following training in improvers but not in non-improvers. But the N170 amplitude pattern in improvers continued to differ from the N170 amplitude pattern across hemispheres seen in typical readers. Finally, we observed a positive relation between the decrease in N170 amplitude and gains in reading fluency. Collectively, the results that emerged from the present study indicate the sensitivity of N170 amplitude to reading fluency and its potential as a predictor of reading fluency acquisition.