Effects Of Structural Connectivity Research Articles

Cognitive reserve moderates Alzheimer’s disease‐related tauopathic mechanism on cognition mediated by structural connectivity networks

AbstractBackgroundCognitive reserve (CR) is the capacity of an individual to maintain cognitive function despite brain damage (Stern et al., 2002). It moderates the effect of Alzheimer’s disease (AD)‐related brain damage on cognition, which is difficult to demonstrate using residual analysis. Recent research has shown a strong effect of tauopathy on the brain damage (Renaud La Joie et al., 2020), but how the CR affects this relationship is still unknown.MethodWe obtained 121 amyloid‐positive individuals, including 15 cognitive unimpaired (CU) individuals, 44 patients with mild cognitive impairment (MCI), and 58 AD. We first identified structural connectivity subnetworks where the relationships between edges’ weights (the number of streamlines) and tauopathy (global cortical tau standard uptake value ratio, standardized by the mean and standard deviation of the amyloid‐negative CU individuals) were modified by the years of education, as a proxy for cognitive reserve, using the network‐based statistics. We chose a subnetwork where its total connectivity significantly mediated the effect of the tauopathy on memory score, based on the Baron and Kenny method (Baron, Kenny et al., 1986). Through the path analysis, we verified the moderated mediation model, in which the moderating effects of education were added to the mediation model.ResultOne subnetwork whose edges were significantly affected by the tauopathy and moderation of education showed partial mediation in the tauopathic mechanism on cognition. The moderated mediation model based on the total connectivity of the subnetwork showed an appropriate model fit (CFI = 0.999, SRMR = 0.006) and a significant moderating effect on both stages of the indirect effect path of mediation when tested using the bootstrap method with 10000 resamples. The simple slope and intercept analyses implied that the highly educated individuals on the AD continuum show higher memory function than the lower educated individuals in the absence of tauopathy, but this score decreased more rapidly as tau increased.ConclusionWe conclude that education modifies the effect of tauopathy on structural connectivity as well as the effect of structural connectivity on cognition when AD‐related tauopathy affects memory score through the structural connectivity subnetwork.

Does structural connectivity facilitate movement of native species in Australia’s fragmented landscapes?: a systematic review protocol

Habitat fragmentation and accompanying isolation effects are among the biggest threats to global biodiversity. The goal of restoring connectivity to offset these threats has gained even greater urgency under the looming spectre of climate change. While linear corridors have been the most commonly proposed solution to these issues, it has become increasingly recognised that structural connectivity exists in different forms with a variety of characteristics. We previously conducted a systematic review from 2008-2010 to collate and synthesise evidence regarding the relationship between these different types of structural connectivity and the actual movement of native Australian plants and animals (i.e., functional connectivity). Our previous review produced a number of management recommendations but also identified significant knowledge gaps. Given that empirical research into connectivity has become even more common since the original review and that it has been more than five years since the original literature searches, the time is ripe for an update of that review. We will update our previous systematic review by repeating a thorough search for both published and unpublished evidence on the effects of structural connectivity on animal and plant movement through heterogeneous landscapes. We will slightly broaden the scope of the original review by including data on semi-aquatic species as well as terrestrial ones. Studies will be included if they: 1) contain data on a terrestrial or semi-aquatic native Australian species; 2) have at least one study site that contains some form of structural connectivity between otherwise isolated patches of habitat; and 3) include data on movement of species through the connectivity or data that allow inference of movement (or the lack thereof). We will repeat the analyses carried out for the original review which used hierarchical linear modelling to assess the effects of numerous sources of heterogeneity (e.g., type of connectivity, width of connection, ecosystem type, taxonomic group, and many other characteristics of the species, habitat, and connectivity) on the amount of movement observed in a landscape. If increased sample sizes allow we will also carry out additional meta-analyses, which were not possible with the original dataset.

Effects of management and structural connectivity on the plant communities of organic vegetable field margins in South Korea

AbstractField margins are an important component of the agri‐environment as they contribute to maintaining ecosystem functions and protecting biodiversity. Field margin structure, landscape attributes, and management practices have been examined as determinants of plant species diversity and composition for mainly cereal field margins; however, relatively little is known about their influence on vegetable field margins. We selected three types of field margins (each n = 4; non‐managed connected to forests, non‐managed isolated, and isolated and managed margins with mowing and organic herbicide) adjacent to organic vegetable crop fields and recorded the species richness and abundance of all vascular plants. The effects of structural connectivity, weed control management, and margin width on the community composition, species richness, and diversity were examined using multivariate statistical techniques. Plant community composition was clearly explained by structural connectivity between field margin and forest, as well as by weed control management. In contrast, species richness of functional guilds was influenced by connectivity and margin width, but not by weed control management. All communities had similar numbers of summer and fall blooming nectar‐ and pollen‐producing plants, an important source of pollination services. In addition, each community of field margin types, despite different species composition, had similar levels of Shannon diversity and evenness. Our results suggest that habitat arrangement is important for determining community composition in field margins. Management practices may be important in determining dominance patterns of individual species. A combination of various margin types and widths may be beneficial for biodiversity conservation and ecosystem services.