Enhanced contribution of SK channels in nonactivated population of neurons after operant learning. A, B, Example traces showing the effect of SK channel antagonism on mAHP currents in FosGFP⁻ neurons in the test group. Summary graph shows larger SK contribution to the mAHP in day 10 FosGFP⁻ neurons (*p < 0.05, day 1 FosGFP⁻: n = 10 cells/6 rats; day 10 FosGFP⁻: n = 9 cells/6 rats). C, Example traces showing larger effect of SK channel antagonism on repetitive firing in FosGFP⁻ day 10 neurons from the test group. D, Summary graph showing the percentage increase in firing after SK channel antagonism in FosGFP⁻ neurons (*p < 0.05, day 1 FosGFP⁻: n = 10 cells/6 rats; day 10 FosGFP⁻: n = 9 cells/6 rats).