Prestimulus Whole-Brain Functional Connectivity Underpins McGurk Perception
Poster No:
2035
Submission Type:
Abstract Submission
Authors:
Vinsea A V Singh1, Vinodh Kumar2, Arpan Banerjee1, Dipanjan Roy3
Institutions:
1National Brain Research Centre, Manesar, Haryana, 2Penn State College of Medicine, Hershey, PA, 3Indian Institute of Technology (IIT), Jodhpur, Rajasthan
First Author:
Co-Author(s):
Introduction:
Perception is influenced by external stimuli and the brain's internal state (Kayser et al., 2016). This internal state is reflected in spontaneous neural (or prestimulus) activity from specific brain regions associated with McGurk perception (Keil et al., 2012). Moreover, previous studies indicate that, along with cross-modal perception regions, there exists a large-scale functional network that shapes the McGurk illusion (Kumar et al., 2020). However, in what way these whole-brain functional networks in the prestimulus duration drive McGurk perception remains unknown. To address this, we explored an available EEG dataset (Kumar et al., 2020) wherein we computed prestimulus imaginary coherence across different frequency bands at both the sensor and source space.
Methods:
18 right-handed participants reported their subjective perception to the McGurk stimulus (audio /pa/ with visual /ka/; illusion /ta/) while their EEG was recorded. We examined differences in prestimulus (Fig. 1A) pairwise imaginary coherence (Nolte et al., 2004) between illusory and non-illusory perception trials at both sensor and source spaces. Sources at different frequency bands were estimated using dynamic imaging of coherent sources (DICS) beamformer (Gross et al., 2001) and parcellated using automated anatomical labelling (AAL) atlas. Cluster-based permutation test with the Fisher's Z transformation (Maris et al., 2007) and quantile thresholding was applied to determine significant differences at the sensor and source levels, respectively. Source time series were reconstructed by projecting trial-wise time series to the spatial filter of significant parcels.
Results:
Time-averaged global coherence computed at the sensor space revealed significant differences in whole-brain functional connectivity (FC) across different frequency bands. We observed a significantly lower theta (t = -0.387, p < 0.001), alpha (t = -0.419, p < 0.001), and beta (t = -0.305, p < 0.001) coherence, and a higher gamma coherence (t = 0.330, p < 0.001) prior to illusory percept (Fig. 1C). Pairwise sensor imaginary coherence showed significant changes in connectivity (p < 0.001) across the whole brain, particularly for the beta coherence before illusory percept (Fig. 1D). Moreover, significant differences in sources estimated between the two trial conditions revealed that along with unisensory (here occipital and temporal) and multisensory integration area: the superior temporal gyrus (STG), higher-cognitive areas like frontal and parietal regions are also involved in shaping the McGurk perception (Fig. 2A). These results were further validated with source FC analysis (Fig. 2B), wherein imaginary coherence between these regions were computed. Prior to illusory perception, we observed a strong theta FC between frontal and parietal brain regions, a strong alpha FC between frontal and occipital regions, a strong beta FC between temporal and frontal regions, and a strong gamma FC between occipital and frontal regions.
Conclusions:
Our study provides compelling evidence that prestimulus whole-brain functional connectivity underpins the perception of the McGurk illusion, highlighting a complex interplay between neural networks across frequency bands. A stronger theta FC between frontal-parietal regions might indicate a shift in sensory precision (Cavanagh & Frank, 2014) before illusory perception. A stronger alpha FC between frontal-occipital regions reflects attention modulation shift to upcoming visual input (Klimesch, 2012) leading to illusory perception. A stronger beta FC between frontal-temporal regions is associated with better sensory integration (Griffiths et al., 2019). And a stronger frontal-occipital gamma FC is associated with visual attention shift (Hipp et al., 2011) before illusory perception. Overall, this study offers new insights into the neural mechanisms underlying McGurk perception.
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural) 2
EEG/MEG Modeling and Analysis
Multivariate Approaches
Segmentation and Parcellation
Perception, Attention and Motor Behavior:
Perception: Multisensory and Crossmodal 1
Keywords:
Cognition
Electroencephaolography (EEG)
Multivariate
Perception
Source Localization
Other - Coherence
1|2Indicates the priority used for review
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Kayser, S. J., McNair, S. W., & Kayser, C. (2016). Prestimulus influences on auditory perception from sensory representations and decision processes. Proceedings of the National Academy of Sciences, 113(17), 4842-4847.
Keil, J., Müller, N., Ihssen, N., & Weisz, N. (2012). On the variability of the McGurk effect: audio-visual integration depends on prestimulus brain states. Cerebral Cortex, 22(1), 221-231.
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