Fig. 5. Different relationships between pairs of synchronous excitatory postsynaptic potentials (EPSPs). V₁ is the recording from one of the neurones and V₂ is the recording from the other. (A) Simultaneous recordings from paired neurones showing pairs of synchronous EPSPs. (B) Amplification of two pairs of EPSPs from the first traces boxed in A, with different amplitudes but similar rise times. (C) In the second two pairs of synchronous EPSPs boxed in A, the amplitudes of EPSPs in V₂ were fractions of those in V₁ and the EPSPs had slower rise times, suggesting their propagation from V₁. (D) The relationship between the rise times of synchronous pairs of EPSPs in normal saline solution (N=60). (E) The relationship between the rise times of synchronous pairs of EPSPs in the presence of 1 mmol l^-1 Mg²⁺ in the external solution in a different neurone (N=52). Fast times in V₁ clearly correlated with slow times in V₂ and vice versa.