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Poster Session B: Wednesday, August 13, 1:00 – 4:00 pm, de Brug & E‑Hall

Balanced Gamma Oscillations Support Ultra-Slow Dynamics in the Cortex at Rest

Francisco Páscoa dos Santos¹, Jorge F Mejias¹; ¹University of Amsterdam

Presenter: Francisco Páscoa dos Santos

While it has been suggested that gamma ($\sim$40Hz) oscillations are an important driver of the spontaneous dynamics of the large-scale cortical networks, whole-brain models often neglect fast excitatory AMPA synapses, responsible for the generation of gamma rhythms through reciprocal excitatory-inhibitory (E-I) interactions. Importantly, these interactions are balanced through homeostatic plasticity mechanisms, ensuring stable activity. However, the joint role of gamma oscillations and E-I balance in supporting large-scale cortical dynamics has not been tested systematically. Therefore, we built a large-scale model of the human cortex with E-I homeostasis and fast and slow excitation through AMPA and NMDA receptors, respectively. By selectively knocking out fast excitation and E-I homeostasis, we demonstrate that models with both features better reproduce the resting-state dynamics of the human cortex, measured through ultra-slow blood-oxygenation-level–dependent (BOLD) signals. While EI homeostasis ensures the emergence of empirical connectivity networks, their dynamic aspect is best captured in models with gamma oscillations generated by AMPA-mediated excitation. Therefore, our results help elucidate the emergence of collective dynamics in the cortex, advancing balanced gamma oscillations as a fundamental generative mechanism behind ultra-slow fluctuations of cortical activity.

Topic Area: Brain Networks & Neural Dynamics

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