Fig. 5.

The relationship of PP plasticity (EPSP₂/EPSP₁) to the initial EPSP amplitude. A, Graph showing PP plasticity at different frequencies. For clarity only PP plasticity with values of <2.5 is shown. B, The relationship of PP plasticity to the initial EPSP amplitude is shown at 20 Hz, when connections that show an inverse relationship between initial EPSP amplitude and plasticity (P1 connections, ▪) are plotted separately to connections that have PP plasticity positively related to EPSP amplitude (P2 connections, ■). Notice that above 2 mV the EPSP was not related to PP plasticity in either type of connection. The inset shows sample traces of paired-pulse plasticity from P1 and P2 connections at 20 Hz.