**4.4 SRV-2W**

SRV-2W is prepared for analysis of heart rate variability (HRV). I describe detail of the HRV in the next session. Breafly, this software detects R waves and calculated the R-R interval tachogram as the raw HRV in sequence order as shown in Fig. 7. Lorentz plots are also able to display.

Fig. 7. Tachogram of the R-R interval (left) and example of Lorentz plots.

From this tachogram, the average and instantaneous power spectra are obtained by the fast Fourier transform as shown in raight and left of Fig. 8, respectively. The software calculates many index of values of HRV as shown in Fig. 8.

Fig. 8. Examples of average power spectrum (left) and 75 instantaneous power spectra (right) in mouse.
