Figure 3
Movie watching induces inter-subject synchronization (A) Average inter-subject similarity index (ISI) of each participant in resting-state (RS), scrambled movie, and movie watching conditions. Similarity indices were not different than zero in non-movie conditions, indicating a chance-level co-occurrence of patterns among participants throughout the whole duration. On the other hand, participants in the movie condition showed higher similarity index values, indicating increased co-occurrence of the patterns compared to chance. Each dot represents a participant. Stars denote statistical significance after correction for multiple comparisons using Bonferroni procedure. (B,C) Average ISI of each participant computed over the first (B) and second (C) half of the fMRI scan during resting-state, scrambled movie watching, and movie watching conditions. While ISI did not differ between condition during the first half of the fMRI scan (F(2) = 1.73, p = 0.19), ISI during movie watching was significantly higher compared to resting-state (t(39) = 8.49, p < 0.0001) and scrambled movie (t(39) = 7.6, p < 0.0001) conditions. ISI during resting-state and scrambled movie conditions were not statistically different (t(39) = 0.41, p = 1). (D) The occurrence probability of the patterns during the first (left) and the second (right) half of the fMRI recording in movie watching, resting-state and scrambled movie watching conditions. While no significant interactions were found between the condition and the pattern probabilities during the first half of the scan (F(6) = 1.81, p = 0.1), a significant interaction was observed in the second half (F(2) = 13.00, p < 0.0001). Pattern 2 showed increased probability during movie watching compared to resting-state (t(156) = 5.09, p < 0.0001) and scrambled movie watching (t(156) = 6.43, p < 0.0001) and Pattern 1 was more frequent during scrambled movie watching (t(156) = 5.20, p < 0.0001) and resting-state (t(156) = 3.82, p = 0.0006) compared to movie watching. Patterns 3 and 4 did not differ between conditions.
