Salicylate and quinine selectively increase spontaneous firing rates in secondary auditory cortex.

This study presents firing rates for simultaneously recorded spontaneous and stimulus driven multi-unit activity in primary auditory cortex (AI), anterior auditory field (AAF) and secondary auditory cortex (AII) in cats before and after application of salicylate or quinine. From 21 cats, in three cortical areas simultaneously, a total of 1533 multi-unit files were obtained. The data suggest (1) that both salicylate and quinine significantly increase spontaneous firing rates in AII, whereas in AI and AAF both quinine and salicylate reduced the spontaneous rate; (2) the effect of both drugs was to increase spontaneous rates for recording sites with high characteristic frequency (CF) and a tendency to decrease them for low CF sites; (3) the mean stimulus driven firing rates were not affected by either drug except for a decrease produced by quinine in AI; (4) changes in driven firing rate were positively correlated with changes in spontaneous firing rates. This suggests that tinnitus inducing agents selectively increase spontaneous firing rates in the extralemniscal pathway.