Connectivity concepts in diffusion and functional MRI

In this talk we will describe and contrast the basic concepts of structural connectivity, functional connectivity, and effective connectivity. Structural connectivity relates to the networks of physical connections. Diffusion MRI (dMRI) has recently gained tremendous popularity and is especially promising for imaging the white matter in the brain. Functional connectivity is based on measuring patterns of correlated activity in fMRI time series. We will describe how eigenimages or spatial modes can be used to estimate these spatial patterns of activity. Effective connectivity is also a concept from fMRI and describes networks of directional effects of one neural element over another. Connectivity in dMRI is often described by results from tractography. Tractography methods can broadly be divided in deterministic and probabilistic methods, and in this talk we will discuss the most popular ones.