Neural network model and simulations showing effects of altering theta and gamma contributions on excitatory output neuron and downstream neuron activity. (A) Schematic showing connectivity in the neural network model together with the coefficient variables representing AMPA (AM), NMDA (NM) and GABAA (GA) receptors (INs = slow and INf = fast inhibitory neurons, Ex = excitatory neurons; lower case letters indicate direction of connectivity - s = INs, f = INf and e = Ex - i.e. NMes = NMDA receptor activated by connection from Ex to INs neurons). (B) Responses to both a ramped and white noise stimulus (top. Iapp = 0.8) (top panel) made by excitatory neurons (second panel)), LFP (third panel), the power contribution of different frequencies across the theta/gamma range (fourth panel), the downstream neuron (fifth panel) and coupling of theta phase and gamma amplitude (bottom panel). Data in the three columns are from a single run of the model using different parameter settings (Left, shallow theta-nested gamma with a theta/gamma ratio 3.4:1; middle, deep theta-nested gamma with a theta/gamma ratio 2.7:1; right, minimal gamma with a theta/gamma ratio of 10:1).