Figure 4. A depressing connection onto a layer III pyramidal cell without release-independent depression.

Although there is slight second EPSP facilitation in this connection, third and fourth EPSPs in trains were depressed (not illustrated). A, facilitation of the second EPSP relative to the average first EPSP, with recovery at longer intervals. This depression is not, however, independent of release. Following first spike failures second EPSPs are further facilitated (B), but after large first EPSPs, second EPSPs are depressed (C) relative to average first EPSPs (grey traces). These responses can be explained by release-dependent depression with some facilitation.