Functional magnetic resonance imaging (fMRI) is a technique used to measure brain activity. Activity can be measured in response to a task or when the subject is in a resting state, that is, when there is no direct stimulus applied. Resting-state scanning is typically performed to investigate the interregional relationships between spatially disparate areas of the brain, that create networks of regions which appear to be working together. The dysregulation of these networks has been implicated in certain diseases states, such as Alzheimer’s, depression, and schizophrenia. This provides an opportunity for functional connectivity to potentially be used as a diagnostic or prognostic tool for these diseases. However, these tests have yet to be applied in the clinic due to a lack of sensitivity in detecting disease states.

A possible explanation for its lack of clinical success may be the lack of behavioural constraints placed on subjects in resting-state scanning, allowing them to drift into a variety of different states of mind. These states are most likely inconsistent across people during the scan and can therefore cause increases in variability of the measures. Increased variability may cause the networks in healthy people to look more different than they are, making it difficult to separate identify features separating them from individuals with disease.

However, a recently popularized technique has attempted to use movies to synchronize the states of individuals during the scan. Using movies, researchers have shown that brain activity is synchronized across subjects based on the time locked events of the movie. In this study, we investigated the effects of movie watching on variability of functional connectivity and compared it to what is observed in the resting state. We hypothesized that movie watching would result in less variable networks across individuals than the resting state because of the mental constraints placed upon individuals being scanned.

The results of the study demonstrated that movie watching led to less variable functional connectivity across the brain compared to resting-state scanning, confirming our hypothesis. Future work is needed to investigate whether the reductions in variability lead to more sensitive tests for disease.