The statistical results in brain activation during (a) NW, (b) WCT, and (c) WMT, respectively.

<p>The <i>t</i> values of significant activations with FDR correction for the multiple comparison in early or late phase are color-coded under the axis for each channel. The averaged dynamics of HbO (red curves), HbR concentrations (blue curves), and Hbdiff level (green curves) are also displayed at each channel. The horizontal solid lines depict the concentration level of zero, and the vertical solid lines label the time of zero for the task onset.</p

Maintaining Gait Performance by Cortical Activation during Dual-Task Interference: A Functional Near-Infrared Spectroscopy Study

<div><p>In daily life, mobility requires walking while performing a cognitive or upper-extremity motor task. Although previous studies have evaluated the effects of dual tasks on gait performance, few studies have evaluated cortical activation and its association with gait disturbance during dual tasks. In this study, we simultaneously assessed gait performance and cerebral oxygenation in the bilateral prefrontal cortices (PFC), premotor cortices (PMC), and supplemental motor areas (SMA), using functional near-infrared spectroscopy, in 17 young adults performing dual tasks. Each participant was evaluated while performing normal-pace walking (NW), walking while performing a cognitive task (WCT), and walking while performing a motor task (WMT). Our results indicated that the left PFC exhibited the strongest and most sustained activation during WCT, and that NW and WMT were associated with minor increases in oxygenation levels during their initial phases. We observed increased activation in channels in the SMA and PMC during WCT and WMT. Gait data indicated that WCT and WMT both caused reductions in walking speed, but these reductions resulted from differing alterations in gait properties. WCT was associated with significant changes in cadence, stride time, and stride length, whereas WMT was associated with reductions in stride length only. During dual-task activities, increased activation of the PMC and SMA correlated with declines in gait performance, indicating a control mechanism for maintaining gait performance during dual tasks. Thus, the regulatory effects of cortical activation on gait behavior enable a second task to be performed while walking.</p></div

The statistical results in difference of brain activation for the three comparisons of (a) WCT vs. NW, (b) WMT vs. NW, and (c) WCT vs. WMT.

<p>The <i>t</i> values of significant differences with FDR correction for the multiple comparison in early or late phase are color-coded under the axis for each channel. The averaged dynamics of Hbdiff level for different tasks (green for NW, red for WCT, and blue for WMT) are also displayed at each channel. The horizontal solid lines depict the concentration level of zero, and the vertical solid lines label the time of zero for the task onset.</p

Segmentation results using the HC-EM-MoMG method for a patient with ICA stenosis.

<p>(a) Consecutive trans-axial DSC-MRI (12^th to 35^th second). (b) Right-lateral neck angiogram illustrated 99% stenosis on the right ICA labeled by the white arrows. (c) Another cerebral angiogram in anterior-posterior projection at the early arterial phase with the contrast injection from the aortic arch. The white arrow pointed out the delayed perfusion on the right ICA. (d) A trans-axial T₂-weighted MR image at the similar slice location with the DSC-MRI. (e) A trans-axial Diffusion-weighted image confirms no infarct or stroke on the slice. (f) Segmented results shows nine hemodynamic components, namely artery (red), gray matter (green), white matter (brown), CSF and cp (gray), right ICA stenosis induced dArtery (pink), dGM (yellow), dWM (light brown), vein and sinus (blue), and artifact (dark blue). (g) The averaged signal-time curves of corresponding tissues. (h) rCBV map (scale unit is ml⋅100 g<i>⁻</i>¹). (i) rCBF map (scale unit is ml⋅100 g<i>⁻</i>¹⋅min<i>⁻</i>¹). (j) MTT map (scale unit is second).</p

The hemodynamic parameters of segmented areas for the patient with moyamoya disease.

<p>The hemodynamic parameters of segmented areas for the patient with moyamoya disease.</p

The averaged dynamics of HbO (red curves), HbR concentrations (blue curves), and Hbdiff level (green curves) at the left PFC (Channel 1) during (a) WMT and (b) WCT.

<p>The horizontal solid lines depict the concentration level of zero, and the vertical solid lines label the time of zero for the task onset. The early and late phases are defined as the periods of 5 to 20 s and 21 to 50 s after the task onset, respectively. The error bars represent the corresponding standard errors of mean.</p

Segmentation results using the HC-EM-MoMG method for a patient with moyamoya disease.

<p>(a) Consecutive trans-axial DSC-MRI (15^th to 38^th second). (b) Right cerebral angiography at early arterial phase on lateral projection shows stenosis of the distal internal carotid artery, proximal segments of the anterior and middle cerebral arteries (red arrows). The moyamoya vessels are seen in the basal ganglia region (blue yellow). The prominent branches of external carotid artery (arrowheads) form the extracranial collaterals. (c) Another arterial phase angiogram taken at 1.5 seconds after (a) shows the late arrival blood supply (arrows). Her right parietal region is less blood-irrigated (arrowheads). (d) A trans-axial T2-weighted MR image shows abnormal high signals in her parietal-occipital region (arrows). (e) Diffusion-weighted image confirms an acute infarct with diffusion restriction (arrows). (f) Segmented results shows eight hemodynamic components, namely artery (red), gray matter (green), white matter (brown), CSF (gray), ischemic or infarct area (purple), areas supplied by collateral arteries with risk of infarct (cyan), vein and sinus (blue), and artifacts (dark blue). (g) The averaged signal-time curves of corresponding tissues demonstrated that the artery arrived earliest with maximum T2* signal drop followed by the GM or vein+sinus, WM or CSF, risk of infarct, and infarct. (h) rCBV map (scale unit is ml<b>⋅</b>100 g<i>⁻</i>¹). (i) rCBF map (scale unit is ml<b>⋅</b>100 g<i>⁻</i>¹⋅min<i>⁻</i>¹). (j) MTT map (scale unit is second).</p

The averaged classification ratesstandard deviations (in percentage) for Monte Carlo simulations resulted from the EM-MoMG method with 2 different initials.

*<p>NF: noise-free.</p

Statistics of gait performance between 3 walking conditions.

<p>*The significance was defined as <i>p</i><0.016 (Bonferroni correction for multiple testing).</p><p>Statistics of gait performance between 3 walking conditions.</p

The averaged classification ratesstandard deviations (in percentage) for Monte Carlo simulations resulted from the EM-MoMG method initialized by the results of HC on the whitened simulated data with different delayed time, dispersion and various SNRs.

<p>The percentage of impaired tissue number of voxels is 25%.</p>*<p>NF: noise-free.</p