Aging alters the timing and magnitude of sharp wave ripple activity in CA1.

A. Spontaneous sharp wave ripples recorded from stratum pyramidale of CA3c (black) and mid-distal CA1 (blue-adult; magenta-aged). Representative traces from three mice per age group are shown. B. Magnitude squared coherence (MSC) was not significantly different between age groups, although the phase coherence between CA3 and CA1 was increased in aged slices compared to adult slices (inset). Dashed line represents the 95% significance threshold (0.12). Error bands are SEM or circular SEM. The inset shows phase coherence in the 0.5–10 Hz frequency band, with mean MSC as the vector lengths and circular mean phase coherence as the vector angles. C. Top: Examples of sharp wave ripples segmented from the continuous recordings. The traces were selected at random from the adult and aged data sets and then sorted by amplitude for the figure. Bottom: Waveform averages of sharp waves and ripple oscillations. Ripples were filtered (100–500 Hz) and temporally aligned by their peak negative voltages before averaging. D. Summary comparison of sharp wave and ripple characteristics between aged and adult slices. Top left: frequency (events per minute). Top right: CA3–CA1 delay (peak to peak time difference). Bottom left: waveform amplitude. Bottom right: ripple RMS power. Sharp waves were more frequenct in aged CA3, whereas CA1 sharp wave ripple activity was temporally delayed and smaller in magnitude in aged slices compared to adult slices. *p<0.05; **p<0.01.