In this study, Breakdown of Brain Connectivity Between Normal Aging and Alzheimer’s Disease: A Structural k-Core Network Analysis, they looked at brain connectivity in a normal brain that was aging and a brain that has Alzheimer’s disease. In this study, they referred to the K-core as the structural backbone of the network. They thought that the K-core was an important way to look at how the K-core value would help with the understanding on how the connections in the brain work. “The k-core decomposition outputs a network core that consists of highly and mutually interconnected nodes.” (Daianu et al, 2013)
This image is from the study that shows the actual K core connections in the brain. (Daianu et al, 2013)
They said that when a K-core has a low value, that the K-core would not be highly connected because that would indicate a low degree number. When the K-core value had a higher number, then that indicated that they were more central in the network. For this study, they selected a K value of 18, which means that the nodes that have a degree of 18 or more are the ones that will be kept, and the ones that have a degree less than 18 will be removed.
The nodes in this study are the different regions of the brain, and the edges are the connections in the brain, which are shown by the different fibers. They made a matrix which showed the connections, they had a total of 111 subjects they looked at. After looking at the K-cores in the network, they were able to look at disease in the brain. “First, the k-core loses nodes drastically as disease progresses, so the number of nodes present where asymmetry can be detected is falling rapidly.” (Daianu et al, 2013) Since the nodes in this study are the regions of the brain, this shows that the regions of the brain are affected by Alzheimer’s disease compared to the brain image they looked at of individuals with a normal aging brain. “The k-core did indeed enhance the disease effects, as the entire k-core was ‘‘lost’’ in the left hemisphere of AD subjects. These findings are important to locate brain regions that change with disease progression.” (Daianu et al, 2013)
This image is a good representation of how the diseased neurons do not look as connected to the brain as the healthy neurons do.
This is to be expected, as with Alzheimer’s, “abnormal deposits of proteins form amyloid plaques and tau tangles throughout the brain, and once-healthy neurons stop functioning, lose connections with other neurons, and die.” (nia.gov) With this study, the K-core provided valuable information that showed them the areas of the brain where connections were lost. This is important in finding out which regions of the brain are most affected by this disease.
Alzheimer’s Disease Fact Sheet. (n.d.). Retrieved from https://www.nia.nih.gov/health/alzheimers-disease-fact-sheet
Daianu, M., Jahanshad, N., Nir, T. M., Toga, A. W., Jack, C. R., Weiner, M. W., & Thompson, P. M. (2013). Breakdown of Brain Connectivity Between Normal Aging and Alzheimer’s Disease: A Structural k-Core Network Analysis. Brain Connectivity, 3(4), 407-422. doi:10.1089/brain.2012.0137