Synchrony of CA3 pyramidal cell oscillators. A, Dual cell-attached recordings from neighboring CA3 pyramidal cells (PC1 and PC2) in a P18 rat hippocampal slice after 8.5 mm [K⁺]_o application. Superimposed traces of 25 consecutive bursts illustrate synchronous burst onset and increasing of the spike-to-spike interval variance as a consequence of spike frequency adaptation. B, Cross-correlation analysis of the intraburst spike timing (bin size, 0.5 msec) reveals high-frequency oscillations with a period of 3-10 msec (100-350 Hz).