Symmetry's Edge in Cortical Dynamics: Multiscale Dynamics of Ensemble Excitation and Inhibition

Creating a quantitative theory for the cortex presents challenges and raises questions. What are the significant scales--micro, meso, or macroscopic? What are the interactions--pairwise, higher order, or mean-field? And what control parameters are relevant--noisy, dissipative, or emergent? We suggest an approach inspired by advances in understanding matter. This involves identifying invariances in neuron ensemble dynamics, searching for order parameters connecting key degrees of freedom and distinguishing macroscopic states, and pinpointing broken symmetries to uncover emergent laws when neurons interact and coordinate. Using multielectrode and multiscale neural recordings, we measure population-level ensemble Excitation/Inhibition (E/I) balance, differing from the input-level E/I balance of single neurons, to study collective behavior in large neural populations. We investigate a set of parameters that can assist us in differentiating between various functional system states (during wake/sleep cycle) and pinpointing broken symmetries that serve different information processing and memory functions. Furthermore, we identify pathological broken symmetries that result in states like seizures.