Phase-dependent Brain Activation of the Frontal and Parietal Regions During Walking After Stroke - An fNIRS Study

Abstract

BackgroundRecovery of walking post-stroke is highly variable. Accurately measuring and documenting functional brain activation characteristics during walking can help guide rehabilitation. Previous work in this area has been limited to investigations of frontal brain regions and have not utilized recent technological and analytical advances for more accurate measurements. There were three aims for this study: to characterize the hemodynamic profile during walking post-stroke, to investigate regional changes in brain activation during different phases of walking, and to related brain changes to clinical measures.MethodsFunctional near-infrared spectroscopy (fNIRS) along the pre-frontal, premotor, sensorimotor, and posterior parietal cortices was used on twenty individuals greater than six months post-stroke. Individual fNIRS optodes were digitized and used to estimate channel locations on each participant and short separation channels were used to control for extracerebral hemodynamic changes. Participants walked at their comfortable pace several times along a hallway while brain activation was recorded. Exploratory cluster analysis was conducted to determine if there was a link between brain activation and clinical measures.ResultsSustained activation was observed in the pre-frontal cortex with the ipsilesional hemisphere showing greater activation compared to the contralesional side. Sensorimotor cortex was active during the early, acceleration stage of walking only. Posterior parietal cortex showed changes in activation during the later, steady-state stage of walking. Faster gait speeds also related to increased activation in contralesional sensorimotor and posterior parietal cortices. Exploratory analysis clustered participants into two distinct groups based on their brain activation profiles and generally showed that individuals with greater activation tended to have better physical outcomes.ConclusionsThese findings can guide future research for obtaining adequate power and determining factors that can be used as effect modifiers to reduce inter-subject variability. Overall, this is the first study to report specific oxygenated and deoxygenated hemoglobin changes in frontal to parietal regions during walking in the stroke population. Our results shed light on the importance of measuring brain activation across the cortex and show the importance of pre-frontal, sensorimotor, and posterior parietal cortices in walking after a stroke.

Recombination of the right cerebral cortex in patients with left side USN after stroke: fNIRS evidence from resting state

“…Our findings are line with Li et al study, which demonstrated that the brain networks of acute stroke patients exhibit reduced cosmopolitan structure and fewer longrange connections compared to those of healthy individuals (57). Similar research has discovered a correlation between small-world characteristics in the inferior cerebral cortex region of RS and motor function among patients (58). Studies have demonstrated that there is an inverse relationship between motor function and the clustering coefficient of the brain network (35).…”

Premotor and Posterior Parietal Cortex Activity is Increased for Slow, as well as Fast Walking Poststroke: An fNIRS Study

“…fNIRS data were continuous sampled at 4.36 Hz through Aurora 1.4 (NIRx Medical Technologies, Berlin, Germany). The probe configuration for this experiment was similar to our previous studies [9,20,21] with 48 long separation channels (∼30-35 mm apart) and 8 short separation channels (8 mm apart). Two different distances were chosen to control for extracerebral systemic changes such as breathing, heartbeat, and mayer waves [22].…”

“…To date, the impact of stroke on functional activation changes with speed modulation is unknown. Previous studies have shown indications of asymmetric brain activations with greater ipsilesional prefrontal [9], contralesional sensorimotor [9,10], and contralesional posterior parietal [9] cortices relating to faster walking speeds poststroke. The changes in the amplitude of activation during walking at different speeds poststroke are also unclear.…”

Frontal and parietal cortices activation during walking is repeatable in older adults based on fNIRS

“…The specific steps included ( Fig. 2 ): (1) Converting the original data into optical density; (2) Using principal component analysis (PCA) for signal filtering; (3) Using Motion standard deviation and spline interpolation methods to remove motion artifacts, and excluding stimuli that fall within the time points identified as motion artifacts from hemodynamic response function calculation [ 22 ]; (4) Using bandpass filtering (0.01 Hz–0.1HZ) to remove physiological noises such as respiration, heartbeat, blood pressure and baseline deviation; (5) Converting optical density to changes in blood oxygen concentration using the modified Beer-Lambert law (with a partial path length factor (PPF) of 6.0 [ 23 , 24 ]); (6) Eliminating irrelevant stimuli outside the defined variables; (7) Using the block-average method, with the average concentration in the first 5 s [ 25 , 26 ] before the task begins used as the baseline, and averaging the concentration for all sample points within the first 25 s post-task initiation; (8) For baseline correction, selecting the most sensitive HbO 2 index with a larger variation range and better signal-to-noise ratio to represent the hemodynamic changes in the brain region, and subtracting baseline HbO 2 from HbO 2 within 25 s post-task initiation for normalization [ 27 , 28 ]. The resulting △HbO 2 mean value represents the brain activation during the task.…”