“…It is generally accepted that changes in mini frequency are a consequence of presynaptic modulations, whereas amplitude variations mainly correlate with postsynaptic modifications. As shown by several studies in various CNS areas, changes in spontaneous activity are not always paralleled by similar modifications of evoked responses; in the dorsal horn, for example, opposite effects have been observed, with an increase of spontaneous activity and a decrease of evoked responses (see, e.g., Chen & Gu, 2005;Engelman, Anderson, Daniele, & MacDermott, 2006;Tomoyose, Kodama, Ono, & Tanabe, 2014). These discrepancies could be explained in part by the different mechanisms involved in transmitter release: evoked release always depends on action potentials and calcium entry into the terminal, whereas minis are action potential independent and can occur also in the absence of extracellular calcium.…”