Video 12.3j Variable Activity. The electrode enters around cell 5 and the BAC neurons. After a long initial volley of action potentials, the membrane potential settles around −65 mV and action potentials cease, revealing an oscillating potential with a period around 2.5 s. During this, postsynaptic potentials are clearly visible. Eventually, the membrane depolarizes slightly and action potentials appear atop the oscillations.