Controlling the Axon The cellular mechanisms and circuits involved in gamma oscillations in the brain are not fully understood. Dugladze et al. (p. 1458 ) simultaneously performed patch-clamp recordings in the soma and axon of hippocampal pyramidal neurons during gamma oscillations in brain slices. Under these conditions, pyramidal cells were divided into two electrogenic compartments: the soma fired at low frequency, whereas, in the axon, ectopic action potentials were generated at higher frequencies. This functional separation was maintained by highly active axoaxonic interneurons. Powerful inhibition of the axon initial segment by these axoaxonic cells prevented the backpropagation of ectopic action potentials to the somatodendritic compartment. However, when the overall excitatory drive to pyramidal cells was high, normal orthodromic action potentials were generated.