# Neurofeedback Effects on EEG Connectivity among Children with Reading Disorders: I. Coherence
## 2 Materials and Methods
### Participants  
Sample sizes were calculated with G*Power 3.1 software ([[https://www.psycholo-gie.hhu.de/arbeitsgruppen/allgemeine-psychologie-und-arbeitspsychologie/gpower](https://www.psycholo-gie.hhu.de/arbeitsgruppen/allgemeine-psychologie-und-arbeitspsychologie/gpower)]([https://www.psycholo-gie.hhu.de/arbeitsgruppen/allgemeine-psychologie-und-arbeitspsychologie/gpower](https://www.psycholo-gie.hhu.de/arbeitsgruppen/allgemeine-psychologie-und-arbeitspsychologie/gpower)) accessed on 7 February 2023). Based on an effect size (Cohen's d) of 0.86 [40], a 1:1 ratio between the sample sizes of the two groups, a one-sided type I error rate of 0.05, and a power (1-\(\beta\) error probability) of 0.8, 18 participants per group were necessary for the comparison between independent groups in the first stage of this study. For the second stage of this study, four participants per group were required for a one-sided type I error rate of 0.05 and a power of 0.8, considering the results reported by [PERSON] et al. [43]. A total of 204 children from different public and private schools in Queretaro, Mexico, were evaluated. They were referred by social workers, who, based on the opinion of the teacher and the child's school grades, identified children who had reading problems and children with good academic performance (children from the same classrooms who had grades of 85 or higher in all subjects). The parents of the identified children were summoned to meetings where the research project was explained; it was stressed that the child's participation must be voluntary and that it was not appropriate to force the child. Parents of 144 children with reading problems and 60 children with good academic performance attended the meetings and later the Laboratory of Psychophysiology, where the project was explained again and doubts were solved. All the children and their parents interested in participating signed informed consent forms. In the first session, parents were given a structured interview, while the Wechsler Intelligence Scale for Children 4 th edition [72] was administered to the child in a separate room. Children with reading problems with IQs less than 80 and children with good academic performance with IQs less than 90 were excluded to rule out intellectual disability, as specified by the DSM-5 in the D criterion, and to ensure that the children in the neurotypical control group had an average IQ. Then, the following assessments were administered: a neuropediatric exam, the Mini-International Neuropsychiatric Interview for Children and Adolescents (MINI Kid) [73; 74]; the reading scale of the Child Neuropsychological Assessment-2 (ENI-2) [75], standardized for the Mexican population; and a resting-state EEG under the eyes-closed condition. In total, 43 right-handed volunteers aged 7 to 11 years were included in this study. In the first stage of this study, two groups were considered: one including 25 children diagnosed with a reading disorder (RD group, n = 25, age = 8.84 \(\pm\) 1.06, 9 girls, 8 born preterm, of which 3 were early premature, IQ = 93.92 \(\pm\) 13.12), in which the child had a percentile of 9 or less in at least one reading subscale, and the other including 18 children with typical development (TD group, n = 18, age = 8.83 \(\pm\) 0.92, 9 girls, 1 late premature, IQ = 106.1 \(\pm\) 8.7), in which all children had percentiles greater than 35 in all reading subscales. Differences in IQ were observed between groups (t = 3.7325, \(p\) = 0.0008, d = 0.955). No differences were found in age or gender ratio. The children included had no severe socioeconomic or cultural disadvantages that could affect their EEG (mother or guardian had at least completed primary school, and theper capita family income exceeded 50% of the minimum wage) [76]. They had no hearing impairments, and those who had visual difficulties (five children in the RD group and one in the TD group) used lenses to correct them. No children presented neurological or psychiatric pathology, except for RD. No children were medicated.