Figure 3

Dynamics of GABA/Glutamate receptor time constant and cell-to-cell excitation/inhibition connectivity balances during normal waking and sleep deprivation.

(A) Neural Mass Modeling in Dynamic Causal Modeling (DCM) decomposes a cortical area into 4 neuronal subpopulations: superficial and deep pyramidal cells, spiny stellate cells and inhibitory interneurons. Each subpopulation projects to the other subpopulations via excitatory (solid lines) and inhibitory (dashed lines) connections and have inhibitory feedback-loops controlling neuronal gain. Furthermore, DCM include 3 common synaptic ionotropic receptors time constants (AMPA, NMDA, GABAa receptor). To derive putative markers of excitation/inhibition balance, we derived two key indices. The first index comprised the time constants of GABAaR and glutamatergic AMPAR and NMDAR. The second index used cell-to-cell population connectivity parameters to estimate connectivity strength and balance between stellate cells, deep pyramidal cells and inhibitory interneurons. (B) GABA/Glutamate receptor time constant balance (z-scored parameters) varied significantly with time, with more glutamatergic drive around the circadian wake-maintenance zone and more GABAergic drive during the biological night. (C) Excitation/inhibition cell-to-cell connectivity parameter balance (z-scored parameters) varied significantly across time, with relatively more inhibition around the circadian wake-maintenance zone and relatively more excitation during the biological night.