Before revision:  The analysis and visualization of weighted graphs are inherently challenging , and thus it is often of use to only examine edges which are deemed significant. There are several methods for extracting from a weighted graph an unweighted or signed backbone which retains only the significant edges.
After revision:  The analysis and visualization of weighted graphs are inherently challenging , and thus it is often useful to examine the 'backbone', an unweighted subgraph containing only the most significant edges.