Neuromodulatory Control of Gamma Oscillations Enables Temporal Precision and Cortical Discriminability

Neuromodulatory signals reshape cortical dynamics, but the computational mechanisms by which they alter population-level coordination and input sensitivity remain unclear. Here, we construct a biophysically grounded mean-field network model to investigate how acetylcholine (ACh) modulation alters gamma oscillations, excitatory-inhibitory phase coupling, and thalamus-like stimulus-evoked responses in cortical microcircuits. We show that cholinergic modulation increases excitatory and inhibitory firing rates, gamma-band synchrony and burst duration nonlinearly, but slows oscillation frequency. Upon thalamus-like pulse stimulation, ACh enhances encoded information, spectral power, burst duration, and excitatoryinhibitory coupling, but weakens thalamus-like stimulationevoked response gain and entropy nonlinearly with effective modulation threshold of 15Hz. These findings identify a unified mechanism by which ACh reshapes cortical computation by selectively enhancing temporal precision and stimulus discriminability through nonlinear reorganization of excitatoryinhibitory phase dynamics and input gain.