Three autoregulatory parameters, A) phase difference, B) gain, and C) step response, derived from the transfer function are plotted.

<p>H (: right side and : left side), L (: affected side and : unaffected side), and S (same legends as L) denote healthy controls, large-artery atherosclerosis group, and small-artery occlusion group, respectively. The first column shows that all parameters in the healthy group from both sides indicate that autoregulation is intact. There is evident positive phase difference. The shape of high-pass filter can also be speculated. The step response, H-C), shows that cerebral blood flow velocity quickly returns to the baseline level within approximately 4 seconds if a unit step change of arterial blood pressure is induced. In the second column, the parameters changes asymmetrically. Dynamic cerebral autoregulation on the affected side is substantially reduced than the unaffected side with decreased phase difference, flattened gain, and slower return of cerebral blood flow velocity in response to a step change of arterial blood pressure. In the last column, this series of subplots show that autoregulation is worsen bilaterally when comparing with the healthy controls.</p

Statistical distributions of the autoregulatory parameters for each category are shown above.

<p>A) Phase difference (PD) from the affected side in the large-artery atherosclerosis group is significantly lower than the contralateral side as well the healthy group. PD from the small-artery occlusion group is bilaterally lower than those in the healthy group but there is no difference within the group. B) No statistical difference is detected using gain. C) The results of the slope of step response agree with the findings in PD. Flatter slope (the value of the slope of step response is closer to zero) is observed within the affected side in large-artery atherosclerosis group than in other conditions. The slope in the small-artery occlusion group is also flatter than the healthy controls only. H, L, and S denote the three groups as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093213#pone-0093213-g001" target="_blank">Figure 1</a>. Rt and Lt stand for right and left side, respectively, for the healthy controls. U and A denote unaffected and affected sides, respectively, for the patients. For each box plot, the central mark is the median and the edges of the box are the 25th and 75th percentiles, the whiskers extend to the most extreme data points which are not outliers, and the outliers are plotted individually as ‘○’. <b>^*</b>denotes <i>P</i><0.05 for comparing between two sides within the same group. <b>^†</b>denotes <i>P</i><0.05 for comparing with the overall of healthy group.</p

Baseline characteristics.

<p>Baseline characteristics.</p

Phase difference (PD), gain and slope of step response in patients and controls.

<p><b>*</b>and <b>^†</b>denote the same statistical meaning as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093213#pone-0093213-g002" target="_blank">Figure 2</a>.</p