Fig. 9. Long-term potentiation induced in two PE1 neurons (A,B) by pairing tetanus to the K-cells with simultaneously depolarizing the PE1 neuron. The broken lines indicates a tetanus, dotted lines a tetanus paired with hyper-polarization of the PE1 neuron, and bold lines a tetanus paired with depolarization. Test stimuli were applied at intervals of 20 s. The stimulus artefacts mark the test pulses. (Ai,Bi) The results for the amplitude of summed EPSPs in mV. The maximum of the dc component was measured as EPSP amplitude. Eight consecutive test stimuli were averaged. (Aii,Bii) Mean of the number of spikes to eight consecutive test stimuli. Values are means ± S.D.; box, S.E.M. Where only filled circles are shown all eight values were the same. Notice the draught about 20 min after the pairing of the tetanus with depolarization (see text). The ordinate gives the dc amplitude (Ai,Bi) and number of spikes (Aii,Bii) elicited by a single stimulus, and the abscissa time in min (notice the different scales in the two graphs, and the high value of summed EPSPs before the application of a tetanus in the neuron of A).