Prediction and verification of nonlinear sleep spindle harmonic oscillations

•We model sleep spindles using a corticothalamic neural field model of the brain.•Nonlinearity in the thalamic relay nuclei produces a spindle harmonic oscillation.•We have observed the spindle harmonic in pilot EEG data.

This paper examines nonlinear effects in a neural field model of the corticothalamic system to predict the EEG power spectrum of sleep spindles. Nonlinearity in the thalamic relay nuclei gives rise to a spindle harmonic visible in the cortical EEG. By deriving an analytic expression for nonlinear spectrum, the power in the spindle harmonic is predicted to scale quadratically with the power in the spindle oscillation. By isolating sleep spindles from background sleep in experimental EEG data, the spindle harmonic is directly observed.