We applied resting-state functional magnetic resonance imaging (rfMRI) combined with graph theory to analyze 90 regions of the infantile small world neural network of the whole brain. We tried to get the following two points clear:① whether the parameters of the node property of the infantile small world neural network are correlated with the level of infantile intelligence development; ② whether the parameters of the infantile small world neural network are correlated with the children's baseline parameters, i.e., the demographic parameters such as gender, age, parents' education level, etc. Twelve cases of healthy infants were included in the investigation (9 males and 3 females with the average age of 33.42±8.42 months.) We then evaluated the level of infantile intelligence of all the cases and graded by Gesell Development Scale Test. We used a Siemens 3.0T Trio imaging system to perform resting-state (rs) EPI scans, and collected the BOLD functional Magnetic Resonance Imaging (fMRI) data. We performed the data processing with Statistical Parametric Mapping 5(SPM5) based on Matlab environment. Furthermore, we got the attributes of the whole brain small world and node attributes of 90 encephalic regions of templates of Anatomatic Automatic Labeling (ALL). At last, we carried out correlation study between the above-mentioned attitudes, intelligence scale parameters and demographic data. The results showed that many node attributes of small world neural network were closely correlated with intelligence scale parameters. Betweeness was mainly centered in thalamus, superior frontal gyrus, and occipital lobe (negative correlation). The r value of superior occipital gyrus associated with the individual and social intelligent scale was -0.729 (P=0.007); degree was mainly centered in amygdaloid nucleus, superior frontal gyrus, and inferior parietal gyrus (positive correlation). The r value of inferior parietal gyrus associated with the gross motor intelligent scale was 0.725 (P=0.008); efficiency was mainly centered in inferior frontal gyrus, inferior parietal gyrus, and insular lobe (positive correlation). The r value of inferior parietal gyrus associated with the language intelligent scale was 0.738 (P=0.006); Anoda cluster coefficient (anodalCp) was centered in frontal lobe, inferior parietal gyrus, and paracentral lobule (positive correlation); Node shortest path length (nlp) was centered in frontal lobe, inferior parietal gyrus, and insular lobe. The distribution of the encephalic regions in the left and right brain was different. However, no statistical significance was found between the correlation of monolithic attributes of small world and intelligence scale. The encephalic regions, in which node attributes of small world were related to other demographic indices, were mainly centered in temporal lobe, cuneus, cingulated gyrus, angular gyrus, and paracentral lobule areas. Most of them belong to the default mode network (DMN). The node attributes of small world neural network are widely related to infantile intelligence level, moreover the distribution is characteristic in different encephalic regions. The distribution of dominant encephalic is in accordance the related functions. The existing correlations reflect the ever changing small world nervous network during infantile development.
The artificial neural network has the ability of the information processing and storage, good adaptability, strong learning function, association function and fault tolerance function. The research on the artificial neural network is mostly focused on the dynamic properties due to fact that the applications of artificial neural networks are related to its dynamic properties. At present, the researches on the neural network are based on the hierarchical network which can not simulate the real neural network. As a high level of abstraction of real complex systems, the small world network has the properties of biological neural networks. In the study, the small world network was constructed and the optimal parameter of the small word network was chosen based on the complex network theory firstly. And then based on the regulation mechanism of the synaptic plasticity and the topology of the small world network, the small world neural network was constructed and dynamic properties of the neural network were analyzed from the three aspects of the firing properties, dynamic properties of synaptic weights and complex network properties. The experimental results showed that with the increase of the time, the firing patterns of excitatory and inhibitory neurons in the small world neural network didn’t change and the firing time of the neurons tended to synchronize; the synaptic weights between the neurons decreased sharply and eventually tended to be steady; the connections in the neural network were weakened and the efficiency of the information transmission was reduced, but the small world attribute was stable. The dynamic properties of the small world neural network vary with time, and the dynamic properties can also interact with each other: the firing synchronization of the neural network can affect the distribution of synaptic weights to the minimum, and then the dynamic changes of the synaptic weights can affect the complex network properties of the small world neural network.
The research on brain functional mechanism and cognitive status based on brain network has the vital significance. According to a time–frequency method, partial directed coherence (PDC), for measuring directional interactions over time and frequency from scalp-recorded electroencephalogram (EEG) signals, this paper proposed dynamic PDC (dPDC) method to model the brain network for motor imagery. The parameters attributes (out-degree, in-degree, clustering coefficient and eccentricity) of effective network for 9 subjects were calculated based on dataset from BCI competitions IV in 2008, and then the interaction between different locations for the network character and significance of motor imagery was analyzed. The clustering coefficients for both groups were higher than those of the random network and the path length was close to that of random network. These experimental results show that the effective network has a small world property. The analysis of the network parameter attributes for the left and right hands verified that there was a significant difference on ROI2 (P = 0.007) and ROI3 (P = 0.002) regions for out-degree. The information flows of effective network based dPDC algorithm among different brain regions illustrated the active regions for motor imagery mainly located in fronto-central regions (ROI2 and ROI3) and parieto-occipital regions (ROI5 and ROI6). Therefore, the effective network based dPDC algorithm can be effective to reflect the change of imagery motor, and can be used as a practical index to research neural mechanisms.