Temporal evolution of activity and balance between excitation and inhibition during memory performance. A, Example network with negative-derivative feedback only in the first cosine component. B, Grayscale-coded spatiotemporal activity pattern. The x-axis represents time and the y-axis represents the neuronal index parameterized by its preferred cue direction θ. C, Spatial profiles of firing activity at different times corresponding to the orange vertical slices in B. D–F, Close balance between excitation and inhibition during the delay period. The shown neuron receives strong net excitation and inhibition that are balanced in strength. The first cosine Fourier component, but not the constant Fourier component, is maintained by negative-derivative feedback, as indicated in F by the balance of recurrent excitation with recurrent inhibition within this first cosine component. Values in D–F are illustrated for the inputs onto an excitatory neuron at 3 s into the delay period.