Cognitive tasks during walking affect cerebral blood flow signal features in middle cerebral arteries and their correlation to gait characteristics

Neural control of cerebral blood flow: scientific basis of scalp acupuncture in treating brain diseases

Scalp acupuncture (SA), as a modern acupuncture therapy in the treatment of brain diseases, especially for acute ischemic strokes, has accumulated a wealth of experience and tons of success cases, but the current hypothesized mechanisms of SA therapy still seem to lack significant scientific validity, which may not be conducive to its ultimate integration into mainstream medicine. This review explores a novel perspective about the mechanisms of SA in treating brain diseases based on its effects on cerebral blood flow (CBF). To date, abundant evidence has shown that CBF is significantly increased by stimulating specific SA points, areas or nerves innervating the scalp, which parallels the instant or long-term improvement of symptoms of brain diseases. Over time, the neural pathways that improve CBF by stimulating the trigeminal, the facial, and the cervical nerves have also been gradually revealed. In addition, the presence of the core SA points or areas frequently used for brain diseases can be rationally explained by the characteristics of nerve distribution, including nerve overlap or convergence in certain parts of the scalp. But such characteristics also suggest that the role of these SA points or areas is relatively specific and not due to a direct correspondence between the current hypothesized SA points, areas and the functional zones of the cerebral cortex. The above evidence chain indicates that the efficacy of SA in treating brain diseases, especially ischemic strokes, is mostly achieved by stimulating the scalp nerves, especially the trigeminal nerve to improve CBF. Of course, the mechanisms of SA in treating various brain diseases might be multifaceted. However, the authors believe that understanding the neural regulation of SA on CBF not only captures the main aspects of the mechanisms of SA therapy, but also facilitates the elucidation of other mechanisms, which may be of greater significance to further its clinical applications.

Capillary communication: the role of capillaries in sensing the tissue environment, coordinating the microvascular, and controlling blood flow

Historically, capillaries have been viewed as the microvascular site for flux of nutrients to cells and removal of waste products. Capillaries are the most numerous blood vessel segment within the tissue, whose vascular wall consists of only a single layer of endothelial cells and are situated within microns of each cell of the tissue, all of which optimizes capillaries for the exchange of nutrients between the blood compartment and the interstitial space of tissues. There is, however, a growing body of evidence to support that capillaries play an important role in sensing the tissue environment, coordinating microvascular network responses, and controlling blood flow. Much of our growing understanding of capillaries stems from work in skeletal muscle and more recent work in the brain, where capillaries can be stimulated by products released from cells of the tissue during increased activity and are able to communicate with upstream and downstream vascular segments, enabling capillaries to sense the activity levels of the tissue and send signals to the microvascular network to coordinate the blood flow response. This review will focus on the emerging role that capillaries play in communication between cells of the tissue and the vascular network required to direct blood flow to active cells in skeletal muscle and the brain. We will also highlight the emerging central role that disruptions in capillary communication may play in blood flow dysregulation, pathophysiology, and disease.

Lower Thalamic Blood Flow Is Associated With Slower Stride Velocity in Older Adults

Background

Gait deficits are associated with brain atrophy and white matter hyperintensities (WMH) - both markers of underlying cerebral small vessel disease (SVD). Given reduced subcortical cerebral blood flow (CBF) is prevalent in SVD, we tested the hypothesis that regional CBF is positively associated with gait performance among older adults.

Methods

Thirty-two older adults (55-80 years) with at least one vascular risk factor were recruited. We assessed gait during 2 consecutive walking sequences using a GAITRite system: (1) at a self-selected pace, and (2) while performing a serial subtraction dual-task challenge. We quantified CBF using pseudo-continuous arterial spin labeling MRI within 4 regions of interest: putamen, pallidum, thalamus, and hippocampus. We investigated associations between gait characteristics and overall CBF adjusting for age, sex, and height in an omnibus approach using multivariate analysis of variance, followed by regression analysis with each individual region. We also conducted further regression analyses to investigate associations between gait characteristics and frontal lobe CBF. Sensitivity analyses examined how the observed associations were modified by WMH, executive function, and depressive symptoms. A change of 10% in the model's adjusted r² and effect size was considered as a threshold for confounding.

Results

Overall subcortical CBF was not associated with self-paced gait. When examining individual ROI, gait velocity was directly related to thalamic CBF (p = 0.026), and across all gait variables the largest effect sizes were observed in relation to thalamic CBF. In the dual-task condition, gait variables were not related to CBF in either the omnibus approach or individual multiple regressions. Furthermore, no significant associations were observed between frontal CBF and gait variables in either the self-paced or dual-task condition. Sensitivity analyses which were restricted to examine the association of velocity and thalamic CBF identified a cofounding effect of depressive symptoms which increased the effect size of the CBF-gait association by 12%.

Conclusion

Subcortical hypoperfusion, particularly in regions that comprise central input/output tracts to the cortical tissue, may underlie the association between gait deficits and brain aging.

Evaluating Peripersonal Space through the Functional Transcranial Doppler: Are We Paving the Way for Early Detecting Mild Cognitive Impairment to Dementia Conversion?

BACKGROUND

Identifying the patients with mild cognitive impairment (MCI) who may develop dementia (MDC) is challenging. The study of peripersonal space (PPS) by using functional transcranial Doppler (fTCD) could be used for this purpose.

OBJECTIVE

To identify changes in cerebral blood flow (CBF) during motor tasks targeting PPS, which can predict MDC.

METHODS

We evaluated the changes in CBF in 22 patients with MCI and 23 with dementia [Alzheimer's disease (AD) and vascular dementia (VaD)] during a motor task (passive mobilization, motor imagery, and movement observation) in which the hand of the subject moved forward and backward the face.

RESULTS

CBF increased when the hand approached the face and decreased when the hand moved from the face in the healthy controls (HCs). CBF changed were detectable only in patients with MCI but not in those with the AD and those who were MDC after 8-month follow-up. On the other hand, the patients with VaD presented a paradoxical response to the motor task (i.e., a decrease of CBF rather than an increase, as observed in HCs and MCI). Therefore, we found a modulation of PPS-related CBF only in HCs and patients with stable MCI (at the 8-month follow-up).

CONCLUSIONS

fTCD may allow preliminarily differentiating and following-up the patients with MCI and MDC, thus allowing the physician to plan beforehand more individualized cognitive rehabilitative training.

Validating attentive locomotion training using interactive treadmill: an fNIRS study

BACKGROUND

Existing treadmill-based locomotion training, which has been used for gait function recovery, still has limitations, such as less attentive training. Interactive treadmills (ITMs) were developed to overcome these limitations, but it has not yet been verified that ITMs can make the user pay closer attention to walk training.

METHODS

An experimental comparison between ITMs and conventional treadmills was conducted by measuring the level of the user's attention using functional near-infrared spectroscopy (fNIRS). To consider the effect of task complexity on the subject's attention, we provided two (slow and fast) speed conditions for walking on both treadmills.

RESULTS

Both the cortical activity images and oxygenated hemoglobin (oxyHb) changes showed that the level of attention to walking induced by the ITM was significantly higher than that induced by the conventional treadmill. We found that the walking speed on the ITM also affected the level of attention.

CONCLUSION

ITM-based locomotion training would be a promising solution to the limitations of existing treadmill-based locomotion training currently used to improve gait function recovery.

TRIAL REGISTRATION

DGIST-HR-150309-03-02 . Registered 01 March 2015.

Walking While Talking and Risk of Incident Dementia

INTRODUCTION

Walking while talking (WWT) is a performance-based test of divided attention that examines cognitive-motor interactions. The purpose of this study is to examine the predictive validity of WWT for dementia and dementia subtypes.

METHODS

We prospectively studied the associations of WWT performance at baseline with risk of developing incident dementia in 1,156 older adults (mean age: 78.28 ± 5.27 years, 60.7% female) enrolled in the Einstein Aging Study using Cox proportional hazard models. Associations were reported as hazard ratio (HR) with 95% confidence intervals (CI).

RESULTS

Over a median follow-up of 1.90 years (interquartile range: 4.70 years), 85 participants developed incident dementia (53 Alzheimer dementia [AD] and 26 vascular dementia [VaD]). Three gait domains were derived using principal component analysis. Only variability, which loaded heavily for swing time standard deviation (SD) and step time SD, was associated with an increased risk of incident dementia per 1 point increase (HR: 1.24, 95% CI: 1.02-1.54) and VaD (HR: 1.50, 95% CI: 1.06-2.12) after adjusting for demographics, disease burden, mental status, and normal walking velocity. Among eight individual gait variables, only swing time variability SD was associated with increased risk for both incident dementia (HR: 1.35, 95% CI: 1.03-1.77) and VaD (HR: 1.78, 95% CI: 1.12-2.83). Variability and swing time SD were not significantly associated with risk of incident AD.

CONCLUSIONS

Complex walking as assessed by the WWT task is a simple and pragmatic tool for assessing risk of developing dementia, especially VaD, in older adults.

Immediate effect of scalp acupuncture on the gait of patients with subacute intracerebral haemorrhage analysed by three-dimensional motion: secondary analysis of a randomised controlled trial

OBJECTIVE

To investigate the immediate effect of scalp acupuncture on walking pattern, using three-dimensional gait analysis (3D-GA), among patients in the subacute stage of intracerebral haemorrhage (ICH).

METHODS

A subset of 30 patients with subacute ICH participating in a recently published randomised controlled trial who were able to walk independently were assessed by 3D-GA before and immediately after scalp acupuncture treatment (treatment group) or no intervention (control group) and the results presented here as a secondary analysis. The acupuncture manipulation was repeated three times with an interval of 5 min. Spatiotemporal and kinematic parameters during walking were collected and analysed using a 3D motion analysis system.

RESULTS

After treatment, there were significant differences between the treatment and control groups in the spatiotemporal parameters of step length, velocity and cadence (p<0.05) and double-limb support. No significant difference was found in step width. When kinematic parameters were evaluated, the treatment group showed a significantly decreased peak pelvic anterior tilt angle and an increased hip extension angle after scalp acupuncture treatment, whereas the control group demonstrated no temporal changes. There were no significant changes in any other kinematic parameters in either group.

CONCLUSIONS

As the first exploratory study to investigate the effect of the scalp acupuncture on gait performance in patients with subacute ICH, this secondary analysis of a recent randomised trial suggested an immediate effect of treatment on spatiotemporal parameters. Improvement in gait pattern may be associated with a decreased anterior tilt of the pelvis and augmented hip joint motion during walking.

TRIAL REGISTRATION NUMBER

ChiCTR-TRC-08000225; Post-results.