Connecting the dots: Structural and functional connections in healthy and diseased brain

Our brain consists of billions of neurons, and even many more connections between those neurons. These connections are essential for all our daily life functions. One can view these connections in two ways: from a structural and functional perspective. Structural connections are the physical connections between (groups of) neurons, and comparable to train tracts in a train network. Functional connectivity informs on the transfer of signals between (groups of) neurons, similar to the passage of trains over train tracts. In this thesis, we captured structural and functional connections, and their mutual relationship, in the healthy human and rat brain using MRI. In addition, we investigated these connections and their relationships under specific disease conditions, like obsessive-compulsive disorder (OCD) and stroke. From our studies, we obtained new information about the complex organization of structural and functional connections in the brain, which differs between brain regions. In addition, we found that structural and functional connections in the rat brain show specific changes over the lifespan. These changes may explain why specific disorders develop during certain life periods. We identified altered maturation of structural connections in adolescent rats with OCD. Besides, we showed that the organization of structural and functional networks in older rat brains affects the impact of a stroke. This thesis, therefore, provides new insights into the arrangement of structural and functional brain connections and how changes in these connections from young to old age may contribute to disease development.