Fig. 1: Study design and hypotheses.
From: Lower functional hippocampal redundancy in mild cognitive impairment
A Examples of networks with high and low redundancy. The shortest path between nodes i, j do not differ between high and low redundancy in a healthy state. In the case of neurodegeneration (red nodes), a highly redundant network retains a path between nodes i, j, whereas there are no paths between nodes i, j in a low redundancy network. B Sample characteristics of the included subjects. C Representation of the functional parcellation used in the current study made up of 300 nodes representing cortical, subcortical, and cerebellar regions26. The four hippocampal nodes are shown next to the full atlas parcellation, representing anterior (cyan) and posterior (blue) hippocampus. D Three hypothesized relationships between redundancy and cognitive decline. There could be no relationship between redundancy and cognitive decline (gray line), a linear relationship such that redundancy declines linearly across healthy aging, early MCI, and late MCI states (blue line), or a nonlinear relationship, such that redundancy declines between healthy aging and MCI, but plateaus in MCI (red line). Redundancy equation presented above hypothesized relationships, in which redundancy, R, of node pair i,j is represented by the sum of all paths between i,j at length l, up to a maximum path length, L.
