Emergence of communities and diversity in social networks

Communities are common in complex networks and play a significant role in the functioning of social, biological, economic, and technological systems. Despite widespread interest in detecting community structures in complex networks and exploring the effect of communities on collective dynamics, a deep understanding of the emergence and prevalence of communities in social networks is still lacking. Addressing this fundamental problem is of paramount importance in understanding, predicting, and controlling a variety of collective behaviors in society. An elusive question is how communities with common internal properties arise in social networks with great individual diversity. Here, we answer this question using the ultimatum game, which has been a paradigm for characterizing altruism and fairness. We experimentally show that stable local communities with different internal agreements emerge spontaneously and induce social diversity into networks, which is in sharp contrast to populations with random interactions. Diverse communities and social norms come from the interaction between responders with inherent heterogeneous demands and rational proposers via local connections, where the former eventually become the community leaders. This result indicates that networks are significant in the emergence and stabilization of communities and social diversity. Our experimental results also provide valuable information about strategies for developing network models and theories of evolutionary games and social dynamics.This work was supported by the National Nature Science Foundation of China under Grants 61573064, 71631002, 71401037, and 11301032; the Fundamental Research Funds for the Central Universities and Beijing Nova Programme; and the Natural Sciences and Engineering Research Council of Canada (Individual Discovery Grant). The Boston University work was supported by NSF Grants PHY-1505000, CMMI-1125290, and CHE- 1213217, and by Defense Threat Reduction Agency Grant HDTRA1-14-1-0017, and Department of Energy Contract DE-AC07-05Id14517. (61573064 - National Nature Science Foundation of China; 71631002 - National Nature Science Foundation of China; 71401037 - National Nature Science Foundation of China; 11301032 - National Nature Science Foundation of China; Fundamental Research Funds for the Central Universities and Beijing Nova Programme; Natural Sciences and Engineering Research Council of Canada (Individual Discovery Grant); PHY-1505000 - NSF; CMMI-1125290 - NSF; CHE-1213217 - NSF; HDTRA1-14-1-0017 - Defense Threat Reduction Agency; DE-AC07-05Id14517 - Department of Energy)Published versio

Brain Activation of Elite Race Walkers in Action Observation, Motor Imagery, and Motor Execution Tasks: A Pilot Study

Walking plays an important role in human daily life. Many previous studies suggested that long-term walking training can modulate brain functions. However, due to the use of measuring techniques such as fMRI and PET, which are highly motion-sensitive, it is difficult to record individual brain activities during the movement. This pilot study used functional near-infrared spectroscopy (fNIRS) to measure the hemodynamic responses in the frontal-parietal cortex of four elite race walkers (experimental group, EG) and twenty college students (control group, CG) during tasks involving action observation, motor imagery, and motor execution. The results showed that activation levels of the pars triangularis of the inferior frontal gyrus (IFG), dorsolateral prefrontal cortex (DLPFC), premotor and supplementary motor cortex (PMC and SMC), and primary somatosensory cortex (S1) in the EG were significantly lower than in the CG during motor execution and observation tasks. And primary motor cortex (M1) of EG in motor execution task was significantly lower than its in CG. During the motor imagery task, activation intensities of the DLPFC, PMC and SMC, and M1 in the EG were significantly higher than in the CG. These findings suggested that the results of motor execution and observation tasks might support the brain efficiency hypothesis, and the related brain regions strengthened the efficiency of neural function, but the results in motor imagery tasks could be attributed to the internal forward model of elite race walkers, which showed a trend opposed to the brain efficiency hypothesis. Additionally, the activation intensities of the pars triangularis and PMC and SMC decreased with the passage of time in the motor execution and imagery tasks, whereas during the action observation task, no significant differences in these regions were found. This reflected differences of the internal processing among the tasks

Low-Theta Electroencephalography Coherence Predicts Cigarette Craving in Nicotine Addiction

Addicts are often vulnerable to drug use in the presence of drug cues, which elicit significant drug cue reactivity. Mounting neuroimaging evidence suggests an association between functional magnetic resonance imaging connectivity networks and smoking cue reactivity; however, there is still little understanding of the electroencephalography (EEG) coherence basis of smoking cue reactivity. We therefore designed two independent experiments wherein nicotine-dependent smokers performed a smoking cue reactivity task during EEG recording. Experiment I showed that a low-theta EEG coherence network occurring 400–600 ms after onset during long-range (mainly between frontal and parieto-occipital) scalp regions, which was involved in smoking cue reactivity. Moreover, the average coherence of this network was significantly correlated with participants’ level of cigarette craving. In experiment II, we tested an independent group of smokers and demonstrated that the low-theta coherence network significantly predicted changes in individuals’ cigarette craving. Thus, the low-theta EEG coherence in smokers’ brains might be a biomarker of smoking cue reactivity and can predict addiction behavior

Dental and periodontal status of 12-year-old Dai school children in Yunnan Province, China: a cross-sectional study

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Oral health status, knowledge and behaviors of Dai and Bulang ethnic minority groups in Yunnan province, China

The Dai and Bulang people are ethnic minorities in China. Most of them live in Yunnan province, which is located in the southwestern part of China. This study aimed to describe the oral health status, oral health-related behaviors of the 5-and12-year-old children of the Dai and Bulang ethnic groups, the oral health-related knowledge of the 12-year-old Dai and Bulang children living in Yunnan Province, and the factors that influence their oral health status. An oral health survey was conducted on a sample of 5-and 12-year-old Dai and Bulang children in Yunnan, China. The children were selected using a multi-stage and purposeful sampling method for examination by a trained dentist. Dental caries experience was measured using the “dmft/DMFT” index,o ral hygiene status with VPI index and periodontal status with CPI index. A questionnaire was used to collect information on the children’s background, oral health-related knowledge and behaviors. A total of 833 Dai and 723 Bulang 5-year-old children were examined. The prevalence of dental caries among the Dai and Bulang children was 89% and 85%, respectively. There were 49%of the Dai and 38%of the Bulang children had carious tooth with pulp involvement. Their mean (±SD) dmft score was 7.0±5.3 and 5.8±4.9, respectively. Their mean (±SD) dt score was 6.8±5.2 and 5.6±4.8, respectively. Higher dmft scores were found among Dai children who were girls, were currently bottle-fed, took sweet snacks daily, had higher VPI scores, had visited a dentist within last year, and whose father had up to secondary school education. The Bulang children, who took sweet snacks daily, had visited a dentist within the last year and had higher VPI scores had higher dmft scores. A total of 823 Dai and 873 12-year-old Bulang children were surveyed and their prevalence of dental caries was 40% and 35%, respectively. Around 90% of the carious teeth were left untreated. Their mean DMFT (±SD) score was 0.9±1.5 and 0.6±1.1, respectively. Most of them (Dai, 93%; Bulang 71%) had gingivitis and around half of them (Dai, 46%; Bulang, 58%) had dental calculus. The Dai and Bulang children who were girls and those who had visited a dentist during the previous year had higher caries risk. The mean dental knowledge score of the 12-year-old Dai and Bulang children was 7.2 ± 3.7 and 7.8 ± 3.6, respectively. In conclusion, the prevalence of dental caries of the 5-year-old Dai and Bulang children in Yunnan, China was high and most of them were left untreated. The caries experience of the 5-year-old Dai children was associated with gender, father’s education, bottle feeding habits, snacking habits, dental visit behavior, and oral hygiene status. The caries experience of the 5-year-old Bulang children was associated with their snacking habits, dental visit habitsand oral hygiene status. Dental caries was common among the 12-year-old Dai and Bulang children and associated with gender and dental attendance. Most of the decay were left untreated. Their oral health-related knowledge was moderate. Their periodontal condition was poor.published_or_final_versionDentistryDoctoralDoctor of Philosoph

Effects of Parental Migration on Dental Caries of Six- to Eight-Year-Old Children Using Structural Equation Modeling

This cross-sectional study aimed to document the relationship between dental caries, oral health behaviors, and the duration of parental migration in rural Yunnan, China, from September to December 2020. Seven rural primary schools with high parental migration were studied. The oral health status of 500 six- to eight-year-old students was assessed using clinical examination and caregivers’ interviews. A total of 51.8% of the children had at least one parent absent for at least 6 months (left-behind children). Among those children with parental migration <6 months, 40.0% consumed sugar twice or more daily and 82.8% of those with parental migration from 6 to 12 months brushed once a day or less. The percentage of daily sugar consumption twice or more and brushing once or less among those without parental migration were 36.0% and 68.6%. Prevalence of caries in permanent teeth (DMFT) in children without parental migration and those whose parental migration <6 months, 6 to <12 months, and ≤12 months were 30.9%, 20.0%, 28.7% and 19.8%, respectively. Out of several other causal pathways between parental migration and dental caries, our structural equation model delineated that sugar consumption is the important mediator variable. Special education programs may be needed to educate caregivers on sugar consumption for the left-behind children in rural areas