In carefully designed experimental paradigms, cognitive scientists interpret the mean event-related potentials (ERP) in terms of cognitive operations. However, the huge signal variability from one trial to the next, questions the representability of such mean events. In our NeuroImage paper in collaboration with Ghislaine Dehaene (Neurospin, Paris-Saclay), we explored whether this variability is an unwanted noise, or an informative part of the neural response. Our results suggest that the stimulus does not impact « where the system is » as much as it impacts « how the system flows » after stimulus presentation. We propose the term Event-Related Variability (ERV) to collectively describe this remarkable sequential and task-specific organization of variability quenching and boosting events, both between and within trials, which complements the classic descriptions of the modulations of average response (ERP).
Specifically, we took advantage of the rapid changes in the visual system during human infancy and analyzed the variability of visual responses to central and lateralized faces in 2-to 6-month-old infants compared to adults using high-density electroencephalography (EEG). We observed that neural trajectories of individual trials always remain very far from ERP components, only moderately bending their direction witha substantial temporal jitter across trials. However, single trial trajectories displayed characteristic patterns of acceleration and deceleration when approaching ERP components, as if they were under the active influence ofsteering forces causing transient attraction and stabilization (like a ball rolling on a structured landscape with valleys and ridges to cross and fall into).
Importantly, these structured modulations of response variability, both between and within trials, had a rich sequential organization, which in infants, was modulated by the task difficulty and age. Such nontrivial ERV dynamics reveals an immediate richness of structured states in infants comparable to adults, confirming a potential role of variability modulations as a computing resource since the earliest ages.
Highlights
- Stimulus driven modulations of neural variability are richly structured in time.
- Event Related Variability (ERV) patterns are already structured in early infancy.
- ERV patterns depend on task and age (in 2-6 month old infants and adults).
- ERV patterns are not fully explained by induced phase reset or microstate switching.
- Within-trial variability may reflect sampling of a structured dynamical landscape.
To know more:
- Naik, S., Adibpour, P., Dubois, J., Dehaene-Lambertz, G., and Battaglia, D. (2023). Event-Related Variability is Modulated by Task and Development. NeuroImage 276, 120208. 10.1016/j.neuroimage.2023.120208.