The Superior Paraolivary Nucleus

Abstract

Abstract This chapter summarizes the current concepts of the superior paraolivary nucleus (SPON)—a structure embedded in the superior olivary complex in the mammalian auditory brainstem. SPON is driven by input pathways from two of the most temporally secure neurons in the brain: the octopus cells in the cochlear nucleus and the neurons of the medial nucleus of the trapezoid body. These inputs activate spiking activity that marks the onset and offset of sound, the latter based on a rebound depolarization mechanism. This makes the SPON an excellent detector of transient sound energy. Robust detection of the coarse sound pattern over time further gives SPON the capacity to track the temporal envelope of complex sounds with supreme precision. Since the SPON circuitry is constant in mammals and resilient to sensory perturbation, it indicates its high survival value. A possible neuroevolutionary role of SPON in the processing of vocalizations is discussed.