Invited by: Muhammet Ikbal Sahan

Title: Taking a snapshot of the brain: Visual impulse reveals (non)persistent neural activity by perturbation and increasing signal-noise ratio

Abstract: Most common brain imaging techniques are limited to ongoing activity patterns. However, we know that functional connectivity maintains information in the brain. How do we see what is happening in the brain if neurons do not actively fire? Stokes (2015) suggested that the visual impulse perturbation technique acts like a sonar signal used in echolocation, from which structural information (e.g., the ocean floor surface) can be derived. Similarly, in the brain, the visual impulse reveals memoranda embedded in functional connectivity, which might by themselves be activity-silent. In this study, we tested the functions of the impulse perturbation technique in the working memory context. We matched a task-irrelevant feature (spatial frequency) of a visual impulse with memory items (orientation gratings) while equalizing intensity and contrast. Better decoding of WM content in the match condition than in the no-match condition would suggest that the impulse interacts with the actual content within the WM network whether it is maintained with persistent activity or not. Conversely, if no differences between conditions are observed, it may mean that the visual impulse technique`s function is limited to decreasing EEG variance. Results showed an advantage for matching impulses, supporting the former hypothesis that visual impulses work as a neural sonar. Further, although the visual impulse decreased average EEG variance, there was no difference between match and no-match conditions. We conclude that visual impulse perturbation reveals memoranda embedded in functional connectivity, in line with the idea that WM might rely on activity-silent states. I will end my talk with how non-invasive brain perturbation may be useful in other fields of psychology, for example, taking snapshots of the brain during a resting session of psychiatric patients or after the consumption of specific nutrition.