Correlation analysis, more popularly known as functional connectivity, looks for BOLD signal similarity between a seed region (ROI) and the rest of the brain. Be aware of the following limitations when interpreting the results
A. Difference between correlation and causation: The connectivity thus identified is ambiguous with respect to interaction and direction, and does not necessarily indicate direct neuronal connection.
B. Restriction of voxel-wise correlation with only one seed ROI.
C. No temporal delay is considered.
Two type of correlation analysis: