Behavior of primary horizontal canal neurons in alert and anesthetized guinea pigs

The activities of the primary horizontal canal neurons were investigated in alert and anesthetized guinea pigs. The average resting rate in the alert guinea pigs was 47.3 +/- 21.2 spikes/s. This value was significantly higher than that in anesthetized animals which had an average rate of 39.1 +/- 20.5 spikes/s. The average gain from the total of 66 units tested at 0.3-Hz sinusoidal rotation was 0.42 +/- 0.37 spikes/s/degree/s, and this value was the same as that of anesthetized guinea pigs. The average phase lag to the angular acceleration was 57.3 +/- 20.7 degrees in the alert guinea pigs, which was significantly smaller than that in the anesthetized animals. The number of cutoff neurons at 0.3 Hz was 1 out of 67 neurons in the alert guinea pigs and 7 out of 64 neurons in the anesthetized guinea pigs. The functional meaning of these differences in primary semicircular canal neurons is discussed.