Abstract
Visual object recognition arises from a series of spatio-temporal activity patterns within the ventral and dorsal streams. To reveal human brain neural dynamics, Cichy et al. (2014, 2016) integrated measurements of functional magnetic resonance imaging (fMRI) with magnetoencephalography (MEG). Here, we assess the power of this fMRI-MEG fusion method in producing replicable results for visual recognition. First, we evaluated the reliability of the fusion method at capturing the spatiotemporal dynamics of representations by assessing the neural agreement of visually similar experiences within individuals. For this, we collected fMRI and MEG data while participants (N=15) viewed 156 natural images, performing an orthogonal vigilance task. The images were arranged in twin sets (two sets of 78 images each) with pair images sharing high similar verbal semantic description and with no significant difference in low level image statistics between each set. Fusion method revealed highly consistent spatiotemporal dynamics for the twin sets showing neural representations starting in the occipital pole (~70–90ms after stimulus onset), followed by neural representations in anterior direction along ventral stream and up to the inferior parietal cortex in dorsal pathway. Second, we tested the generalizability of the fusion method by replicating Cichy et al. (2016) and comparing the depicted spatiotemporal dynamics with the twins set temporal dynamics. Despite variations in stimulus set and participant groups, we again found highly overlapping spatio-temporal patterns starting in early visual cortex (~70–80ms) and extending to higher perceptual regions around 110–130ms with no significant difference between the two experimental settings. In sum, these results reveal the reliability and generalizability of fMRI-MEG fusion method and demonstrate that this method is an appropriate analytical tool to non-invasively evaluate the spatiotemporal mechanisms of perception.
Acknowledgement: This research was funded by NSF grant number 1532591, in Neural and Cognitive Systems as well as the Vannevar Bush Faculty Fellowship program funded by the ONR grant number N00014-16-1-3116 and the DFG Emmy Noether Grant CI 241/1-1. The experiments were conducted at the Athinoula A. Martinos Imaging Center at the McGovern Institute for Brain Research, Massachusetts Institute of Technology.