Fig. 4

Multiple circadian oscillators in the SCN. a, b Phase-contrast photomicrograph of SCN neurons in a dispersed cell culture (a) and slice culture (b) on a multi-electrode dish. The black squares indicate the 64 electrodes with a size of 50 μm square, with 150 μm separation (a), and 20 μm square, with 100 μm separation (b). c, d Circadian firing rhythms of four representative SCN neurons from a dispersed cell culture (c) and a slice culture (d). Numbers on the right margin of the first lane indicate the firing rate (mean spikes/s in 15 min)