Figure 3.

Median $T{E}_{RESP\stackrel{}{\to }HRV}$ of significant segments for each kind of interaction at 4 Hz vs. lag ($\tau$) in seconds. (a) $RESP=NAS$; (b) $RESP=THO$. Gray lines represent higher interactions in NREM1, while black lines correspond to higher interactions in NREM3. Linear interactions are on the left, for which significant differences using $NAS$ are found at $\tau =2$ and $\tau =4$ s. Nonlinear interactions are on the right, for which significant differences using $NAS$ are found at $\tau =1$ and $\tau =3$ s. No significant differences are found using $THO$.