2.3. Sharp wave-ripples
Glass electrodes (resistance in aCSF: 1-2 MΩ) were placed at pyramidal layer of CA3 and CA1. Data were recorded for ~5 min and 2 min artifact-free recordings were extracted as MATLAB files to be further analysed using a MATLAB-based code (MathWorks, Natick, MA). SW-R analysed as previously described (Çalişkan et al. , 2016). For detection of sharp waves (SW) the data was low-pass filtered at 45 Hz (Butterworth, 8th order). Three times the standard deviation (SD) of the low pass-filtered signal was used as the threshold for event detection. As a second criteria, the minimum interval between two subsequent SW was set to 80 ms. Data stretches of 125 ms centred to the maximum value of the SW event were stored for further analysis. For the analysis of the area under the curve of SW, the points crossing the mean of the data were used as the start and the end points of SW. The SW area was measured using trapezoidal numerical integration of low pass-filtered data. The raw data were band-pass-filtered at 120-300 Hz for analysis of the ripples that are superimposed to SWs (Butterworth, 8th order). Data stretches of 15 ms before and 10 ms after the maximum of SW event (25 ms) were stored for further analysis. Three times the standard deviation (SD) of the band-pass-filtered signal was used as the threshold for ripple detection. The analysis of the ripple amplitude was performed by triple-point-minimax-determination. Ripples were discarded from the analysis, if the difference between falling and rising component of a ripple was higher than 75%. Ripple frequencies were calculated only from subsequent ripples.
Network interactions between CA3 and CA1 during SW-R were analysed as previously described (Çalişkan et al. , 2016). Briefly, (1) CA3-CA1 propagation failure was calculated as the ratio of unconnected SW events in the CA3 and CA1 region within +/- 30 ms time-window; and (2) CA3-CA1 event correlation was analysed via measuring temporal relationship between presumably connected SW events in the CA3 and CA1. The global maximum correlation value within +/- 30 ms time-window was used for statistical comparison.