Abstract
Most fMRI studies investigating smooth pursuit (SP) related brain activity, i.e. BOLD-responses, have used simple synthetic stimuli such as a sinusoidally moving dot. However, real-life situations are much more complex and SP does not occur in isolation but within sequences of saccades and fixations. This raises the question whether brain networks for SP, which have been identified under laboratory conditions, are similarly activated when following moving objects in a movie. Here, we analyzed studyforrest data providing 3T fMRI recordings along with eye tracking data from 15 subjects while watching the Forrest Gump movie (Hanke et al., 2016). Automated eye movement classification across subjects (Agtzidis et al., 2016) resulted in 50.7% (+/− 18.2%) of viewing time spent on fixations, 8.4% (+/− 3.5%) on saccades, and 14.4% (+/− 4.8%) on SP tracking. In order to maintain high specificity, the rest of the samples were left unlabeled or labeled as noise. For fMRI analysis we used an event-related design (SPM 12) modelling saccades and SP as regressors. Contrasts of interest in whole-brain analyses were BOLD-response differences during SP compared to saccades. A threshold of pcorrected < 0.05 FWE was applied for cluster level findings. By this, we identified higher BOLD-response during SP than saccades in V5 bilaterally (right: kE=175, left: kE=93), in middle cingulate extending to precuneus (kE=519), and in an area in the right superior temporal gyrus (kE=86). Higher BOLD-response during saccades than pursuit was observed in V1 (right: kE=112). This is the first report about brain activity specifically related to the most prominent eye movements such as SP and saccades in complex naturalistic situations. Most importantly, we were able to show that bilateral activation of V5, which is the core motion processing area, was related to SP but not saccades.
Acknowledgement: Elite Network Bavaria