Use of three-dimensional movies with surround sound as stimuli during functional magnetic resonance imaging
Naturalistic stimuli such as movies are being increasingly used as stimuli in cognitive neuroimaging studies. One of the advantages offered by movies is that they make it possible to test ecological validity of predictions based on research with more artificial stimulus features. Challenges in data analysis due to inherent complexity of movie stimuli have been eloquently handled by development of novel data analysis methods, including decomposition of the movie stimulus into a set of relevant stimulus time courses that are used as predictors in data analysis. One aspect that has not been tested under neuroimaging settings, however, is the use of three-dimensional movies with surround sound.
In their recent study, Ogawa et al. (2013) presented healthy volunteers with alternating 2D and 3D movie clips with vs. without surround sound during functional magnetic resonance imaging. The surround sound was generated with a custom-build MR-compatible piezoelectric speaker array. Data analysis was carried out by both contrasting the blocked conditions (3D with surround sound, 3D without surround sound, 2D with surround sound, and 2D without surround sound) and by using time courses of the degree of binocular disparity and the number of sound sources as predictors of brain hemodynamic activity.
The authors observed that brain hemodynamic activity was predicted by absolute visual disparity in dorsal occipital and posterior parietal areas and by visual disparity gradients in posterior aspects of the middle temporal gyrus as well as inferior frontal gyrus. The complexity of the auditory space was associated with hemodynamic activity in specific areas of the superior temporal gyrus and middle temporal gyrus. These results are highly exciting per se and, further, given that 3D and surround sound effects are known to increase the immersive effect of movies, this study represents an important step forward by demonstrating the feasibility of using 3D movies with surround sound during functional magnetic resonance imaging.
Reference: Ogawa A, Bordier C, Macaluso E. Audio-visual perception of 3D cinematography: an fMRI study using condition-based and computation-based analyses (2013) PLoS ONE 8: e76003. http://dx.doi.org/10.1371/journal.pone.0076003