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.