Single neuron recordings in dorsal cochlear nucleus (DCN) of awake gerbil

The auditory responses of neurons in the dorsal cochlear nucleus (DCN) are known to be sensitive to anesthesia, and consequently many studies have used an unanesthetized, decerebrate preparation. Decerebration, however, severs multiple descending pathways to the DCN and is traumatic to the brain, and so sensory responses may be influenced. It was possible, by combining sterile surgery, animal conditioning, and mild restraint to allow recordings in awake gerbils (Merionus unguiculatus). Response maps (RMs), post-stimulus time histograms (PSTHs), and responses to notch noise stimuli were recorded in awake gerbils. Some units’ responses were compared to those from previous experiments in anesthetized and decerebrate gerbil preparations. All RM types observed in decerebrate gerbils were also observed in the awake gerbil, with the notable exception of type IV units. Type III units were still the most commonly recorded units. No significant changes were observed in either RM shape or notch noise responses. Although most awake DCN units had spontaneous activity (typically <20 spikes/s), these rates were lower than those in decerebrate gerbils. Type III units’ spontaneous activity rates were significantly different from those in the decerebrate prep (P < 0.05). DCN neurons may be more inhibited in awake gerbils. Although type III units were most sensitive to spectral notches, different unit types seem to respond slightly differently to notch noise. This study indicates that responses of DCN units in awake and decerebrate gerbils are different, though the shapes of RMs are the same.