  Previous research has found that functional connectivity (FC) can accurately
predict the identity of a subject performing a task and the type of task being
performed. We replicate these results using a large dataset collected at the
OSU Center for Cognitive and Behavioral Brain Imaging. We also introduce a
novel perspective on task and subject identity prediction: BOLD Variability
(BV). Conceptually, BV is a region-specific measure based on the variance
within each brain region. BV is simple to compute, interpret, and visualize. We
show that both FC and BV are predictive of task and subject, even across
scanning sessions separated by multiple years. Subject differences rather than
task differences account for the majority of changes in BV and FC. Similar to
results in FC, we show that BV is reduced during cognitive tasks relative to
rest.
