Fig. 3.

Up states. Bars below voltage traces represent stimulus presentations. A: induction of an Up state and variance measurements before, during, and after an Up state. B: examples of Up states showing the variety of Up states observed even within the same recording. The first (left) Up state shows how variable the membrane potential (MP) can be during an Up state, making it difficult to be certain if one is observing a single, highly variable state or multiple states without an extended Down state separating them. C: example of a nonspiking Up state and of multiple Up states resulting from one stimulus set presentation. Observe here that a nonspiking Up state of smaller MP deviation is followed by a series of larger, spiking Up states. All appear to result from a single stimulus set presentation. This likely accounts for the clustered firing observed in extracellular recordings shown in Fig. 1. D: hyperpolarizing current injection (black bar) was able to repress Up state while applied, but not to arrest it following cessation. E: depolarizing current injection was able to produce firing (in the example shown, 14 spikes over 1-s depolarization) but not initiate persistent activity or Up state. F: a cell filled with Lucifer yellow following intracellular recording. This cell can be identified as an intermediate DD (DDi) cell by its location and the orientation of its dendritic processes (Giassi et al. 2012c).