## 3 Results on Philadelphia Neuro Developmental Cohort (PNC) Data
### The Identification of Essential Differences of ICNs during Development  
We randomly divide the samples into two parts, 70% training data for two-step feature selection and 30% test data for testing the classification performance of the selected features, and repeat the process for \(M_{1}\) times. With each repetition, the training samples are randomly divided into two parts for \(M_{2}\) times, i.e., 3/4 for feature selection and 1/4 for validating the selected features. Thus, by combining the SVMRFE-CA and the FSCS methods for the current training samples, we obtain the optimal feature subset which possesses the non-redundant information. Then, the frequency of each feature in all the optimal subsets obtained by \(M_{1}\) times is counted. We found that when \(M_{1}\) or \(M_{2}\) is over 20, the selected features are nearly the same. Therefore, we choose \(M_{1}=M_{2}=20\). Finally, among the total 34,716 functional connections, 20,719 are absent, 1859 occur more than 10 times, and 134 present in all the 20 experiments. The 134 connections can be considered as functional connections with the most significant differences during development. Additionally, in order to facilitate the analysis on these 264 ROIs which are identified by [PERSON] et al. (2019), the functional roles to brain regions are assigned from the work of [PERSON] et al. (2019). Based on which, different resting state networks (RSNs) are defined ([PERSON] et al., 2019), which are shown in Figure 4.  
In Figure 4, the 13 RSNs are mainly concerned with the perception of movement, memory, language and other several functions of brain, and they are the sensory/somatomotor network (SSN), cingulo-opercular task control network (COTCN), auditory network (AN), default mode network (DMN), memory retrieval network (MRN), visual network (VN), fronto-parietal task control network (FPTCN), salience network (SN), subcortical network (SCN), ventral attention network (VAN), dorsal attention network (DAN), and cerebellar network (CN), respectively. In which, SSN contains the precuneus, cingulate gyrus, precentral and postcentral gyrus, superior frontal gyrus, and some other brain regions. COTCN contains the middle frontal gyrus, insula, superior temporal gyrus, etc. In DMN, the main brain regions include the posterior cingulate, medial frontal gyrus, parahippocampal gyrus, bilateral lateral temporal lobe. VN mainly contains the middle and inferior occipital gyrus, lingual gyrus and cuneus. FPTCN includes the superior parietal lobule and frontal gyrus. The main regions in SCN are the extra-nuclear, lentiform nucleus and thalamus. VAN is composed of the superior and middle temporal gyrus, inferior frontal gyrus and inferior parietal lobule. Among the 264 ROIs, there exist 28 ROIs with which the functional roles are uncertain, and they are uniformly merged into the uncertain RSN ([PERSON] et al., 2019). For the selected 134 functional connections, which are considered to be significantly associated with the developmental difference, there are 104 within or between the 13 RSNs defined above, and 30 related to the uncertain RSN, i.e., the 13 th RSN. Among the 134 functional connections, 45 of them are significantly strengthened during development, and 89 are notably weakened with age. Figure 5 describes the relationships between the 134 functional connections and the 264 ROIs as well as the 13 RSNs. The colors of the 264 ROIs represent their corresponding RSNs with their names listed on the left. The red lines represent the enhanced functional connections during development, and the blue lines represent the weakened functional connections. In addition, the distributions of the 104 functional connections among the 12 certain RSNs are illustrated in Figure 6, where the thickness of the line represents the number of different function connections, i.e., the thicker the line is, the stronger functional connection is. Furthermore, the enhanced and weakened functional connections are shown in Figure 7 by the BrainNet Viewer toolbox [52]. Figure 4: Resting state network maps.