Figure. 1.

Very fast oscillations (VFOs) occur at the surface of human epileptic brain; in layer 5 of rat neocortex, in vitro, with chemical synapses blocked; and in a detailed network model of neurons coupled by gap junctions, without chemical synapses. (A) Electrocorticography (ECoG) recording from epileptic frontal neocortex (previously unpublished data from patient B of Roopun et al., 2009). The portion marked by “*” is expanded below. Power spectrum is from 1 s of data. Scale bars: 100 µV, 11 s; 10 µV, 100 ms. (B) Upper traces are field and intracellular recordings (IB, or intrinsic bursting cell), showing VFO in layer 5 of rat temporal neocortex in “nonsynaptic conditions”: AMPA, N-methyl-d-aspartate (NMDA), and γ-aminobutyric acid (GABA)_A receptors were, respectively, blocked with 21 SYM2206, AP5, and gabazine. The bath contained kainate, and alkaline artificial cerebrospinal fluid (aCSF) was pressure ejected onto the slice just before the trace begins. Scale bars: 0.1 mV (field), 50 mV (cell), 500 ms. The graph (right) shows pooled incidence plot (bin width 0.5 ms) for 500 field VFO periods with full spike data plotted as the gray line and spikelet data as the black line. The data in the gray box were expanded in the lower left: scale bars 0.2 mV, 40 mV, and 400 ms. Simulation data are shown lower right: field potential of very fast network oscillation (above, spectral peak at 112 Hz), and simultaneous “intracellular recording” (below). Scale bars 50 mV