Figure 1.

One- and two-neuron hypotheses. A, Event A is a complex spike typically observed in the MNTB, composed of A₁ generated by synaptic transmission at the calyx of Held and A₂, which is the action potential of the MNTB neuron. Event B is sometimes observed in the same recordings as event A and resembles A₁ in shape. B, The one-neuron hypothesis proposes that events A and B originate from a single “complex unit” (i.e., a calyx of Held and MNTB neuron). In this case, events A₁ and B should always be separated by a time equal to or greater than the RP. C, The two-neuron hypothesis proposes that events A and B originate from two different neurons: one complex unit giving rise to event A and a second structure in the vicinity of the recording electrode giving rise to event B. Here, events A₁ and B can occur closer together than the refractory period and can overlap (“superposition”). The dashed lines indicate the trigger level use in the triggering algorithm. The long and short dead times used in the triggering algorithm are also illustrated: they are limited by the duration of events A and B, respectively.