What can the topology of white matter structural networks tell us about mild cognitive impairment

The focus of investigation in cognitive disorders has shifted from single regional motifs toward brain networks. White matter connections collectively form the connectome, and provide the underpinnings of distributed patterns of brain activity. We examine findings about large-scale properties of structural networks in mild cognitive impairment (MCI), discuss these in terms of the mechanism of cognitive decline and evaluate potential clinical implications. Networks of patients with MCI exhibit reduced global efficiency, which associates with cognitive performance. The structural core of the connectome remains relatively unperturbed. Some global measures of network structure in MCI lie on a spectrum between healthy aging and Alzheimer's dementia. Connectomics seems ill-equipped to guide diagnosis, but provides measures suitable for monitoring disease progression and treatment effect.