# Neurofeedback Effects on EEG Connectivity among Children with Reading Disorders: I. Coherence
## 4 Discussion
### Children with RDs vs. Children with TD  
Considering the information provided by studies comparing the resting-EEG coherence of children with RD with that of children with TD, it can be hypothesized that children with RDs would show higher coherence values in the delta, theta, and beta frequency bands; these differences could be expressed in areas related to reading, or perhaps children with RDs display compensatory functions. The results partially support this hypothesis because the RD group presented higher coherence values in the delta (left frontoparietal and occipito-occipital coherences) and theta (left frontoparietal, fronto-occipital, and parieto-occipital coherences; and occipito-occipital coherence) frequency bands than the TD group, but no differences between groups were observed in the beta band. Higher delta and theta coherences within regions of the left hemisphere coincide with those reported by [PERSON] et al. [42], [PERSON] et al. [40] and [PERSON] et al. [28]. In addition, decreased frontoparietal delta and theta coherence could point to deficits in the attention-related fronto-parietal network [84; 85]; this would support the fact that children with RDs not only have a specific deficit in reading but also deficits in general domain processes [69; 86]. In the alpha band, it was expected that children with RDs would present higher values of intrahemispheric coherence [29; 41; 42] and lower values of interhemispheric coherence [28; 29; 40]. Among children with RDs and EEG maturational lags in this study, lower intrahemispheric alpha coherences (bilateral frontofrontal coherences and left frontotemporal coherences) and lower interhemispheric alpha coherence were found between the F7 and F8 leads. The results confirm those obtained by [PERSON] et al. [40] in a sample of 84 children with writing-reading disorders (20 of them with TD) and do not match the higher intrahemispheric alpha coherence observed in other studies in dyslexic children [31; 32; 33]. It is necessary to remember that the children included in this study did not have dyslexia but rather a specific reading disorder. In studies conducted on the pediatric population and analyzing EEG coherence, the tendency has been to associate high values of coherence, mainly in the delta and theta bands, with cognitive dysfunction [87]. For example, [PERSON] [88] reported high coherence in children with low IQ scores. In patients with ADHD, [PERSON] et al. [89], [PERSON] et al. [90] and [PERSON] et al. [91] reported higher delta and theta coherences, mainly in frontal regions. Regarding the alpha band, higher IQ performance has been related to higher alpha coherence [88], and lower alpha coherence has been reported in ADHD children [89; 91; 92]. In contrast, in studies conducted in children with learning disorders, the results were not very consistent; this may be because children with learning disabilities are a heterogeneous population [93; 94] and because they frequently have many comorbidities. These comorbidities were excluded from this study but have not been controlled for in other studies. It must be considered that the RD diagnostic criteria have been modified over the years and that all these children with RDs had delayed EEG maturation; the latter contributed to reducing the heterogeneity that could exist within the RD group. The lower alpha coherences between the right frontal regions observed in this study may be explained by the right brain activation described as a compensatory mechanism in children with dyslexia [15; 16]. This mechanism includes the right frontal region (homolog of [PERSON]'s area). These results led to hypothesize the effects of NFB in children with RDs and lagging maturation. NFB was expected to lead to a reorganization of brain interconnections that would manifest as a reduction in delta and theta intra- and interhemispheric coherence and an increase in alpha, intra-, and interhemispheric coherence.