Multiscale Neural Processing of Visual Stimuli

1664 

Abstract Submission 

Richa Richa¹, Bryan Paton², Peter Robinson³, Michael Breakspear⁴

¹The University of Newcastle, Australia, North Lambton, NSW, ²University of Newcastle, New Lambton Heights, New South Wales, ³University of Sydney, Sydney, NSW, ⁴University of Newcastle, Newcastle, N/A

Richa Richa  
The University of Newcastle, Australia
North Lambton, NSW

Bryan Paton  
University of Newcastle
New Lambton Heights, New South Wales

Peter Robinson  
University of Sydney
Sydney, NSW

Michael Breakspear  
University of Newcastle
Newcastle, N/A

Periodic photic stimulation of human volunteers at 10 Hz is known to entrain their Electroencephalography (EEG) signals. This entrainment manifests as an increment in power at 10, 20, 30 Hz. We observed that sub-harmonics' emergence accompanies this entrainment, but only at specific frequencies and higher intensities of the stimulating signal. Neural Mass models and Neural Field Theories have previously been used to explore the dynamics underlying the emergence of such behavior. In our work, we focus on the bifurcation structure of the Jansen and Rit NMM to explore the behavior at a single electrode level and the NFT to further explore the spatial behavior/patterns corresponding to our experimental results.

Healthy adult participants were exposed to visual stimuli at two distinct forcing frequencies and intensities while their EEGs were recorded. We also record the resting state EEG to get a contrast or baseline to assess the effects of stimulation. Following this, Neural Mass Models (NMMs) were used to emulate the experimental findings and to provide a mesoscale perspective on the entrainment phenomena observed on the occipital electrodes. We then probe further into the spatial distribution of these subharmonics with Neural Field Theory.

Our results indicate that stimulation with high-intensity 10 Hz frequency resulted in a pronounced increase in EEG power at 5 Hz, an effect not seen with low-intensity stimulation at the same frequency. Subsequent experiments done with a 6 Hz stimulation did not significantly alter power at 3 Hz, regardless of the intensity. Simulated Neural Mass Models (NMMs) recapitulate these phenomena and provide a plausible mesoscale explanation for the observed experimental results, laying a framework for a deeper understanding of the underlying neural mechanisms. Building on these mesoscopic explanations, we subsequently look at the spatial patterns underlying cortical entrainment with the help of neural field theory simulations.

Our results suggest that the brain's response to rhythmic visual stimuli is intricately dependent on both the intensity and frequency of the stimulation. The bifurcation structure of the Jansen and Rit NMM provides a plausible mesoscopic explanation for these results. This suggests that the bifurcation properties of the NMM mirror similar features possessed by the actual neural masses producing the EEG dynamics. Our more recent NFT simulations provide further insights into large-scale brain dynamics, and highlight the potential for a unifying theoretical framework to understand the brain's complex responses to external stimuli.

Non-Invasive Stimulation Methods Other ²

EEG/MEG Modeling and Analysis ¹

Subcortical Structures

Electroencephaolography (EEG)

Modeling

Sub-Cortical

Thalamus