Figure 2.
Temporal relationships between unit activity and GDPs. A, Two simultaneous fp recordings (fp 1 and fp 2; ∼200 μm apart) under control conditions show synchronous activity associated with slow, negative fp shifts (fGDPs) and unit asynchronous bursts (asterisk) (see Results). B, Cross-correlation histograms of slow, negative fp shifts and unit spikes (bin, 10 ms; 56 fGDPs) obtained from fp 1 and fp 2 recordings of the experiment shown in A. C, Cumulative cross-correlation histograms of individual fp recordings (n = 8) and simultaneous fp and cell-attached (n = 6) recordings. D, Intracellular recording showing intrinsic bursts and an intracellular GDP (arrow). Note that in the given recording, the intrinsic bursts and GDPs can be distinguished by eye, but this is not always the case. E, Two simultaneous fp recordings (bandpass, 1-600 Hz) under control conditions show fGDPs (arrows), which are seen at both recording sites, and unit asynchronous bursts detected only at either site. A concentration of 10 μm NBQX and 40 μm d,l-AP-5 blocks fGDP, but unit bursting is still observed. F, Histogram of fGDP intervals (n = 14 recordings; n = 668 fGDPs; bin, 0.5 s). G, ISI histogram of asynchronous spikes (n = 696 spikes from 5 fp and 3 cell-attached recordings). H, ISI histogram of unit activity in NBQX plus AP-5 ([K+]o = 3-5 mm) obtained from four fp recordings (n = 724 spikes). The bin width is 0.5 s, and the first bar related to intraburst spike intervals is truncated in the histograms in G and H. Arrows in F-H indicate preferred frequency.