Figure 1.

Overview of the recording setup and patterns of discharge activity at different postnatal ages. A, An in vivo preparation for extracellular single-unit recordings. Top and middle, The MNTB was approached by a glass electrode penetrating from the dorsal side through the cerebellum and the brainstem. Bottom, Recordings yielded complex voltage signals consisting of the calyx AP followed by the postsynaptic potential. B–D, Patterns of spontaneous activity at three different ages. The spontaneous rates are indicated in the top row. B, At P8, the spontaneous activity is characterized by discrete bursts of transmission events interrupted by silent or low-activity periods (first row). Within single bursts, the patterned activity is structured further displaying series of 1–5 transmission events in close succession, i.e., mini-bursts (second and third row). Within these mini-bursts complex waveforms exhibited high variability in amplitude and temporal relations of presynaptic and postsynaptic components (third row). The fourth row shows 50 overlaid complex potentials triggered to the presynaptic AP, and the fifth row visualizes in a color plot the variability of the different signal components on the same time scale. The red color indicates the size of the positive phases and the blue color of the negative phases of the complex signal. Shown here is a series of spontaneous discharge activity in its natural occurring succession. The light-colored horizontal stripes indicate transmission events, in which the presynaptic signal component is followed by strongly reduced postsynaptic components. C (P11), D (P28), At older ages the discharge activity becomes more continuous even though bursting discharges can be still present at P11. The complex waveforms shorten and attain their adult-typical, constant shape. AVCN, Anteroventral cochlear nucleus; LSO, lateral superior olive; SR, spontaneous rate.