Neurons in the central nucleus of the main converging station in the auditory midbrain, the central nucleus of the inferior colliculus (ICC) have been shown to display either linear significant receptive fields [1] or both linear and nonlinear significant receptive fields [2]. In this study, we used reverse correlation to probe linear and nonlinear response properties of single neurons in the cat ICC. The receptive fields display areas of stimulus parameters leading to enhanced or inhibited spiking activity, and thus allow investigating the interplay to process complex sound. Spiking responses were obtained from recordings of anesthetized cats in response to dynamic moving ripple (DMR) stimuli [3]. The DMR sound contains amplitude and frequency modulations and allows systematically mapping neural preferences. Spike-triggered average and covariance were computed for the envelope of the DMR, separately for each frequency carrier (range of 0-5.5 octaves). This enables studying processing of the sound envelope, and to investigate whether nonlinearities are more pronounced at the neuron's preferred frequencies versus other frequencies. We find that more than half of the neurons (n:120) display significant nonlinear response properties at least at one frequency carrier. Nonlinearities are dominant at the neuron's best frequency. The nonlinear preferences can have either the same or opposite temporal receptive field pattern (e.g. on-off) as the linear preferences. No relationship to other neural properties such as feature-selectivity, phase-locking, or the like has been found. Thus, these nonlinearities do not seem to be linked to a specific type of neuron but to be inherent to ICC neurons indicating a diverse range of filtering characteristics.

[1] C.A.Atencio, T.O. Sharpee and C.E. Schreiner J.Neurophysiol. 107:2594-603(2012).
[2] S. Andoni and G.D. Pollak J.Neurosci. 31:16529:40(2011).
[3] M. Escabí and C.Schreiner J.Neurosci. 22:4114-4131(2002).