Figure 1.
Multibeam two-photon imaging of the four maturation steps of spontaneous neuronal activity in somatosensory cortical slices from embryonic stages to first postnatal days. A, Two-photon calcium fluorescence images of rat somatosensory cortical slices of the four types of spontaneous activity: calcium spikes (left), cortical synchronous plateau assemblies (cSPAs), cortical early network oscillations (cENOs), and cortical giant depolarizing potentials (cGDPs, right) recorded at E20, P0 (cortical plate), P3 (cortical plate, horizontal slice), and P7 (deeper layers), respectively. White arrows indicate direction of pial surface. B, Automatically detected contours of the cells from the fluorescence images: open contours indicate silent cells, black filled contours indicate cells producing calcium spikes, red filled contours are cSPAs-cells, green filled contours are cENO cells, and blue filled contours are cGDPs-cells; scale bar: 100 μm. C, Raster plots of the activity from the four slices illustrated in A in control ACSF. Each row represents a single cell and each horizontal line the duration of detected calcium transients. Four populations of events can be distinguished as shown by representative fluorescence traces below the raster plots (black: calcium spikes; red: calcium plateaus i.e., cSPA-events; green: cENO-events; blue: cGDP-events). D, Current-clamp recordings (Vrest of approximately −60 mV) in four representative neurons displaying the four types of calcium activities described above. D1, A calcium spike recorded in a neuron at E20. D2, Red: cSPA recorded in a neuron at P0. Note that calcium plateaus are associated to rhythmic membrane potential oscillations as SPAs described in the hippocampus. D3, Green: a cortical ENO. D4, Blue: three successive cortical GDPs.