Changes In Network Composition Research Articles

Age-related differences in network flexibility and segregation at rest and during motor performance

Brain networks undergo widespread changes in older age. A large body of knowledge gathered about those changes evidenced an increase of functional connectivity between brain networks. Previous work focused mainly on cortical networks during the resting state. Subcortical structures, however, are of critical importance during the performance of motor tasks. In this study, we investigated age-related changes in cortical, striatal and cerebellar functional connectivity at rest and its modulation by motor task execution. To that end, functional MRI from twenty-five young (mean age 21.5 years) and eighteen older adults (mean age 68.6 years) were analysed during rest and while performing a bimanual tracking task practiced over a two-week period. We found that inter-network connectivity among cortical structures was more positive in older adults both during rest and task performance. Functional connectivity within striatal structures decreased with age during rest and task execution. Network flexibility, the changes in network composition from rest to task, was also reduced in older adults, but only in networks with an age-related increase in connectivity. Finally, flexibility of areas in the prefrontal cortex were associated with lower error scores during task execution, especially in older adults. In conclusion, our findings indicate an age-related reduction in the ability to suppress irrelevant network communication, leading to less segregated and less flexible cortical networks. At the same time, striatal connectivity is impaired in older adults, while cerebellar connectivity shows heterogeneous age-related effects during rest and task execution. Future research is needed to clarify how cortical and subcortical connectivity changes relate to one another.

Marriage, Social Networks, and Health at Older Ages.

Social relationships in older adulthood have strong connections to health and wellbeing. Connections with social network members and with spouses and long-term partners in particular, have an especially important impact on health. We highlight recent research from the National Social Life, Health, and Aging Project (NSHAP), a nationally representative, longitudinal study of aging in America, to describe the different ways health is produced in social contexts. We first discuss how social network characteristics and marital relationships influence health outcomes and sexuality, and then move on to recent findings about the ways health shapes an individual’s social world. We find that features of a social network, apart from simply its size, have strong effects on health behaviors, and that changes in network composition are associated with changes in health. We show that marriage is uniquely protective against damaging biological processes, and that the quality of a marriage influences health and well-being in nuanced ways. Finally we find that health status is associated with the ability to manage one's social network, and that health status affects the quality of one's marriage. We focus our discussion on new data from Wave 2 that enables researchers to explore how changes in social networks and partner relationships affect health and well-being during the last third of life.

Diffusion Dynamics with Changing Network Composition

We analyze information diffusion using empirical data that tracks online communication around two instances of mass political mobilization, including the year that lapsed in-between the protests. We compare the global properties of the topological and dynamic networks through which communication took place as well as local changes in network composition. We show that changes in network structure underlie aggregated differences on how information diffused: an increase in network hierarchy is accompanied by a reduction in the average size of cascades. The increasing hierarchy affects not only the underlying communication topology but also the more dynamic structure of information exchange; the increase is especially noticeable amongst certain categories of nodes (or users). This suggests that the relationship between the structure of networks and their function in diffusing information is not as straightforward as some theoretical models of diffusion in networks imply.

Developing quality in female high‐technology entrepreneurs' networks

PurposeDespite recognition of the value of networking, there has been little research into the networks of female entrepreneurial practitioners, particularly in the science, engineering and technology (SET) sectors, viewed traditionally as male‐dominated. This paper aims to provide greater insights into the dynamics and quality of female entrepreneurial networks.Design/methodology/approachInsights were derived through a qualitative, in‐depth, interview‐based study of 18 female entrepreneurs operating SET‐based ventures in Northern Ireland. The use of Nvivo as the data analysis tool imposed a discipline and structure which facilitated the extraction of core insights.FindingsAspects investigated include network type and composition; nature and frequency of engagement; and changes in network composition and networking activities through the business lifecycle. The results focus on implications of the findings for issues of quality in networks and their impact on the value of female networks.Practical implicationsAn understanding of these issues offers opportunities to shape government interventions to assist female entrepreneurs embarking on a venturing pathway in SET‐based ventures, or those already operating in business, to be more effective in building, utilising and enhancing the quality of their networking activities.Originality/valueIn exploring networking and issues of quality for female entrepreneurs operating in SET‐based sectors, traditionally viewed as male‐dominated, the paper considers an under‐researched area of the female entrepreneurship literature.

Does Respondent Driven Sampling Alter the Social Network Composition and Health-Seeking Behaviors of Illicit Drug Users Followed Prospectively?

Respondent driven sampling (RDS) was originally developed to sample and provide peer education to injection drug users at risk for HIV. Based on the premise that drug users' social networks were maintained through sharing rituals, this peer-driven approach to disseminate educational information and reduce risk behaviors capitalizes and expands upon the norms that sustain these relationships. Compared with traditional outreach interventions, peer-driven interventions produce greater reductions in HIV risk behaviors and adoption of safer behaviors over time, however, control and intervention groups are not similarly recruited. As peer-recruitment may alter risk networks and individual risk behaviors over time, such comparison studies are unable to isolate the effect of a peer-delivered intervention. This analysis examines whether RDS recruitment (without an intervention) is associated with changes in health-seeking behaviors and network composition over 6 months. New York City drug users (N = 618) were recruited using targeted street outreach (TSO) and RDS (2006–2009). 329 non-injectors (RDS = 237; TSO = 92) completed baseline and 6-month surveys ascertaining demographic, drug use, and network characteristics. Chi-square and t-tests compared RDS- and TSO-recruited participants on changes in HIV testing and drug treatment utilization and in the proportion of drug using, sex, incarcerated and social support networks over the follow-up period. The sample was 66% male, 24% Hispanic, 69% black, 62% homeless, and the median age was 35. At baseline, the median network size was 3, 86% used crack, 70% used cocaine, 40% used heroin, and in the past 6 months 72% were tested for HIV and 46% were enrolled in drug treatment. There were no significant differences by recruitment strategy with respect to changes in health-seeking behaviors or network composition over 6 months. These findings suggest no association between RDS recruitment and changes in network composition or HIV risk, which supports prior findings from prospective HIV behavioral surveillance and intervention studies.

Adjusting for network size and composition effects in exponential-family random graph models

Exponential-family random graph models (ERGMs) provide a principled way to model and simulate features common in human social networks, such as propensities for homophily and friend-of-a-friend triad closure. We show that, without adjustment, ERGMs preserve density as network size increases. Density invariance is often not appropriate for social networks. We suggest a simple modification based on an offset which instead preserves the mean degree and accommodates changes in network composition asymptotically. We demonstrate that this approach allows ERGMs to be applied to the important situation of egocentrically sampled data. We analyze data from the National Health and Social Life Survey (NHSLS).

Can Cultural Worldviews Influence Network Composition?

Most sociological research assumes that social network composition shapes individual beliefs. Network theory and research has not adequately considered that internalized cultural worldviews might affect network composition. Drawing on a synthetic, dual-process theory of culture and two waves of nationally-representative panel data, this article shows that worldviews are strong predictors of changes in network composition among U.S. youth. These effects are robust to the influence of other structural factors, including prior network composition and behavioral homophily. By contrast, there is little evidence that networks play a strong proximate role in shaping worldviews. This suggests that internalized cultural dispositions play an important role in shaping the interpersonal environment and that the dynamic link between culture and social structure needs to be reconsidered.

Changes in network composition and need satisfaction received from different network sectors during the first semester in university

The aim was to investigate changes in composition of students’ social networks and in satisfaction of various needs by different network sectors during the first semester in university. Questionnaires were distributed to 235 first year Turkish students attending Middle East Technical University (METU) at the beginning and end of the first semester. Eighty-eight students lived with and 147 lived away from parents. Network members were grouped into three categories: family members, friends who were students at the university, and friends who were not students at the university. The results were generally consistent with the premise that social networks change with changing contexts during life transitions. More within-university friends and fewer family members and outside-university friends were cited as network members over time. Students living away from families added more new within-university friends to their networks and retained fewer outside-university friends than students living with families. Family members emerged as important providers of both affiliative and instrumental need satisfaction at the beginning of the semester but their importance declined over time. Affiliative need satisfaction obtained from both within- and outside-university friends declined and instrumental need satisfaction from outside- friends university increased over time. Females living with families cited more family members and outside-university friends than females living away from families. Females reported more need satisfaction from their families at the beginning and less need satisfaction from families at the end of the first semester when compared with males. In spite of these time related changes, network stability was also evidenced.

The dynamics of injection drug users’ personal networks and HIV risk behaviors

While studies of the social networks of injection drug users (IDUs) have provided insight into how the structures of interpersonal relationships among IDUs affect HIV risk behaviors, the majority of these studies have been cross-sectional. The present study examined the dynamics of IDUs' social networks and HIV risk behaviors over time. Using data from a longitudinal HIV-intervention study conducted in Baltimore, MD, this study assessed changes in the composition of the personal networks of 409 IDUs. We used a multi-nomial logistic regression analysis to assess the association between changes in network composition and simultaneous changes in levels of injection HIV risk behaviors. Using the regression parameters generated by the multi-nomial model, we estimated the predicted probability of being in each of four HIV risk behavior change groups. Compared to the base case, individuals who reported an entirely new set of drug-using network contacts at follow-up were more than three times as likely to be in the increasing risk group. In contrast, reporting all new non-drug-using contacts at follow-up increased the likelihood of being in the stable low-risk group by almost 50% and decreased the probability of being in the consistently high-risk group by more than 70%. The findings from this study show that, over and above IDUs' baseline characteristics, changes in their personal networks are associated with changes in individuals' risky injection behaviors. They also suggest that interventions aimed at reducing HIV risk among IDUs might benefit from increasing IDUs' social contacts with individuals who are not drug users.

The role and impact of social relationships upon well-being reported by mental health service users: A qualitative study

A number of quantitative studies of people with severe mental illness show that, as with the general population, supportive social relationships are associated with well-being but the nature and causation of this association are unclear. To enhance services' contribution to the social support needs of their clients, this study explores the association qualitatively from the perspective of the lived experience of 27 mental health service users. Social contacts were reported to be both protective and damaging to mental health and it was common for close social relationships in particular to be both supportive and harmful. Loneliness was reported to be a problem, and almost all social contact was valued and perceived as better than none at all. Mental health problems led to changes in network composition and lack of balance in relationships, and this was sometimes difficult to reverse. Clinical implications of the findings are discussed.

Changes in network composition among the very old living in inner London

This article examines changes over time in social network composition among a sample of people aged 85 and over at baseline interview in 1987, who were followed-up two and a half to three years later. Almost half of respondents at follow-up had smaller networks than in 1987, with 19% having fewer relatives in their networks, 30% having fewer friends, and 26% also having fewer confidants. However, for most (84%) there was no change in whether they could name a main helper. Network density (integration) had declined for 30%, a substantial minority. For the remainder there were either increases or no changes. Most of those who needed help with tasks of daily living were given help, and while much of the help was given by relatives, by 1990 professionals were also providing a major part of the help. There were no associations with network change and health or functional ability, or with use of services. Those whose network size had increased were more likely to report at follow-up interview (in 1990) a need for (more) help. Multivariate analysis confirmed that while the greater part of the change in network size was accounted for by changes in numbers of relatives, it was closely followed as an explanatory variable by changes in numbers of friends, indicating that both variables (relatives and friends) account almost equally for changes in network size over time among very elderly people. The research presented here reports a considerable amount of change in network size and structure.

Changes in network composition among older people living in inner London and Essex

This article examines changes over 2 1 2 –3 years in social network composition among three samples of elderly people, and reports on a considerable amount of change in network size and structure. The samples were based in an urban section of inner east London (Hackney) (two samples of people aged 65–84 and 85+ at baseline) and in a semi-rural district of Essex (Braintree) (one sample aged 65–84 at baseline). Most people in all three samples had a social network, although 14% of the 85+ group had no one in their networks by follow-up. Loss of relatives, friends and confidants was greatest, as would be expected, in the 85+ sample. This older sample not only had weaker networks, and suffered the greatest losses to their networks, but they were also far less likely to be engaged in social activities. The younger Braintree sample members had the greatest degree of involvement in social activities, and they also had stronger network structures. Although most members of all three samples could name a main helper, sizeable proportions (21 and 16% of the younger and older Hackney samples, respectively) reported that they had no helper by follow-up, in comparison with just 5% of Braintree sample members. Both the Hackney samples were more likely than the Braintree sample to report wanting more help. The longitudinal analyses showed evidence of gains, as well as stability and loss, among sizeable proportions of sample members. Even among the 85+ sample, of those with no friends at baseline, 34% reported having friends by follow-up. Gains in friendships were also reported by the two younger sample members. However, gains should not be emphasized at the expense of losses, which were considerable. Network losses were due mainly to loss of relatives, rather than friends. Multivariate analysis confirmed that the greater part of the change in network size was accounted for by changes in numbers of relatives. Increases in network size over the time period analysed were associated with increases in need for help—thus size partly expanded in response to need for help. In the older 85+ sample, increases in network size were associated with poorer functional ability over time. The implication of the research for health and social policy is that networks do respond to needs, but the greater loss of relatives from the network over time can have important consequences given that relatives, not friends, provide the practical help.