ABC Seminar: On brain networks and conscious visual perception
In the season opening ABC Seminar, we hear two talks: Dr He on the neural dynamics of conscious visual perception, and Dr Thut on EEG/MEG-guided transcranial brain stimulation.
Initial-state-dependent, robust, transient neural dynamics encode conscious visual perception
Dr. Biyu Jade He, New York University Langone Medical Center
What brain mechanisms underlie conscious perception? A commonly adopted paradigm for studying this question is to present human subjects with threshold-level stimuli. When shown repeatedly, the same stimulus is sometimes consciously perceived, sometimes not. Using magnetoencephalography, we shed light on the neural mechanisms governing whether the stimulus is consciously perceived in a given trial. We observed that depending on the initial brain state defined by widespread activity pattern in the slow cortical potential (<5 Hz) range, a physically identical, brief (30 - 60 ms) stimulus input triggers distinct sequences of activity pattern evolution over time that correspond to either consciously perceiving the stimulus or not. Such activity pattern evolution forms a “trajectory” in the state space and affords significant single-trial decoding of perceptual outcome from 1 sec before to 3 sec after stimulus onset. While previous theories on conscious perception have emphasized sustained, high-level activity, we found that brain dynamics underlying conscious perception exhibit fast-changing activity patterns. These results significantly further our understanding on the neural mechanisms governing conscious access of a stimulus and the dynamical nature of neural activity underlying conscious perception.
Modulating brain oscillations to drive brain functions by EEG/MEG-guided transcranial brain stimulation
Dr Gregor Thut, Institute of Neuroscience and Psychology, University of Glasgow
My talk will outline the opportunities of timing NTBS to ongoing brain activity for enhancing its efficacy. Emerging findings emphasize brain oscillations as promising targets for interventions. This offers a principled framework for influencing the brain-behavior relationship by NTBS. The talk will cover research on frequency-tuned rhythmic TMS or tACS, combined with EEG/MEG recordings, to guide and document the effects of transcranial stimulation, with an emphasis on the visual/attention system. This has been used to address whether brain oscillations merely reflect correlates of the neuronal processes implementing brain functions (are inevitable side-products) or may also have explanatory power as to how the brain operates, and by extension may serve as targets for experimental and clinical interventions. Applications that have helped to shed new light on the neural substrates of sensory sampling and attentional selection are highlighted.
The seminar is followed by coffee and pulla.