Periodic Reporting for period 3 - WAVES (TRAVELING WAVES: Defining the mechanisms allowing attention to occur in space and in time)
Reporting period: 2023-09-01 to 2025-02-28
Brain oscillations have always fascinated both scientists as well as the general public, but their functional role remains ill defined. My previous research contributed to addressing this issue, and demonstrated that oscillations modulate attentional performance periodically in time. Oscillations create periodic windows of excitability, with more or less favorable periods recurring at particular phases of the oscillations. However, attention emerges from systems not only operating in time, but also in space. In the past, researchers have emphasized the temporal aspect of brain oscillations’ behavior. Contemporary investigators have largely continued this trend, rarely considering both temporal and spatial dimensions in their search for the mechanisms linking oscillations and attention. This is the challenge that WAVES is designed to take on. The project seeks to address this essential question: How does the spatio-temporal organization of brain oscillations impact attention? I hypothesize that oscillations propagate over the cortical surface, so-called oscillatory Traveling Waves, allowing attentional facilitation to emerge both in space and time. I propose to test this original hypothesis using a model-based multimodal functional neuroimaging approach including non-invasive and invasive recordings in humans. Interventional approaches will additionally be used to evaluate the degree of causality in the relation between traveling waves and attention. This project could lead to major progress in cognitive psychology and neuroscience by bridging the gap between spatial and temporal dynamics underlying multi-sensory experience. An important methodological development is also expected. The model-based multimodal functional neuroimaging approach that I will develop and evaluate on a large set of data will provide a new methodological guide for the study of brain activity.
Since the beginning of the project, we have made significant progress on the development of a model-based, multimodal, functional neuroimaging approach. We developed a computational model that uses magneto-encephalography (MEG) and electroencephalography (EEG) recordings to distinguish traveling and standing oscillations in the primary visual cortex (V1). The model is specific, that is to say that it can tease apart center-to-periphery and periphery-to-center traveling waves. In another set of experiments, we evaluated the behavioral consequences of the propagation of oscillatory activity in V1 and observed that oscillatory traveling waves periodically modulate behavioral performance across the retinotopic space. We further developed a computational model able to explain the role of attention in such a situation. Finally, some of our results suggest that the direction (occipital-to-frontal or frontal-to-occipital) of long-range traveling waves is dependent on the involved cognitive process (perceptual or attentional).
Our efforts regarding the methodological developments necessary for the successful study of oscillatory traveling waves have yielded ancillary outcomes. We identified a disparity of approaches used in the literature to analyze long-range TW and recognized the need to gather and organize all available methods. In response, we developed a comprehensive toolbox entitled WaveSpace that will provide practical recommendations specific to the type of recorded signal and the type of hypothesis being tested. This will be of great interest to the rapidly growing community of scientists studying TW. We also developed a new method that can measure long-range TW in intracranial EEG recordings characterized by the sparse placement of electrode contacts. This method will be useful to all scientists working with iEEG data and interested in the spatial organization of brain dynamics. It will also allow us to address a classic critique claiming that measured long-range TW in MEG or EEG are artifactual consequences of the recording methods.