Cortical Hemodynamic Responses Research Articles

Individualized post-operative prediction of cochlear implantation outcomes in children with prelingual deafness using functional near-infrared spectroscopy.

The goal of this study was to develop an objective measure and predictor of cochlear implantation (CI) outcomes using functional near-infrared spectroscopy (fNIRS) for young children with prelingual deafness. Sound-evoked hemodynamic responses were recorded from auditory and language-related cortical regions of 47 child CI recipients (35.47 ± 17.24 months of age) using fNIRS shortly after CI activation (0.26 ± 0.30 months). There were four sound conditions (natural speech, instrumental music, multi-speaker babble noise, and speech-in-noise). Post-CI auditory and verbal communication performance was evaluated using clinical questionnaires with caretakers. Both classification and individualized regression models were constructed to predict post-CI behavioral improvement from fNIRS data using support vector machine (SVM) learning algorithms. Auditory cortical responses shortly after CI hearing onset yielded highly accurate prediction of behavioral development in young CI children. For classification models, optimal prediction was achieved using cortical responses to two or more sound conditions, with the highest accuracy of 98.20% (precision = 98.17%, sensitivity = 98.96%, area under the curve of the receiver operating characteristic curve = 99.61%) obtained with the combination of speech, noise, and music stimuli. Similarly, for regression models, best prediction of individual development was achieved using three (highest r = 0.919) or four (r = 0.966) sound conditions. The predictability of cortical responses far outperformed (Cohen's d: 18.56) that of the collection of audiological and demographic parameters (classification accuracy: 0.62) under the same SVM algorithms and could not benefit from the inclusion of the latter. Machine learning models using auditory cortical hemodynamic responses shortly after CI activation were able to predict individualized post-CI behavioral improvement in children with prelingual deafness. Level 5.

Investigating the impact of mental rehearsal on prefrontal and motor cortical haemodynamic responses in surgeons using optical neuroimaging.

Inadequate exposure to real-life operating can impede timely acquisition of technical competence among surgical residents, and is a major challenge faced in the current training climate. Mental rehearsal (MR)-the cognitive rehearsal of a motor task without overt physical movement-has been shown to accelerate surgical skills learning. However, the neuroplastic effect of MR of a complex bimanual surgical task is unknown. The aim of this study is to use functional near-infrared spectroscopy (fNIRS) to assess the impact of MR on prefrontal and motor cortical activation during a laparoscopic knot tying task. Twelve surgical residents performed a laparoscopic knot tying task before and after either mental rehearsal (MR, intervention group) or textbook reading (TR, control group). In both groups, fNIRS was used to measure changes in oxygenated hemoglobin concentration (HbO2) in the prefrontal (24 channels) and motor cortices (22 channels). Technical performance was measured using leak volume, objective performance score and task progression score. MR led to a decrease in HbO2 (reduced activation) in the bilateral prefrontal cortex (PFC), and an increase in HbO2 (increased activation) in the left middle frontal gyrus, left precentral gyrus, and left postcentral gyrus. No discernible changes in activation were observed after TR in either the PFC or motor cortex. Moreover, smaller ΔHbO2 responses in the right PFC and greater ΔHbO2 responses in the left motor cortex were observed in the MR group compared with the TR group. Leak volume was significantly less following MR (p = 0.019), but not after TR (p = 0.347). Mean objective performance score was significantly higher following MR compared with TR (p = 0.043). Mental rehearsal may enhance surgical skill acquisition and technical proficiency by reducing utilization of attentional resources in the prefrontal cortex and improving neural efficiency in motor areas during a laparoscopic surgical task.

Short-term cortical activation changes associated with postural compensation in swallowing

Compensatory strategies used to treat dysphagia, like the chin-down and chin-up positions, are often employed by speech-language pathologists to enhance swallowing safety. However, their effects on cortical neural responses remain unclear. This study aimed to investigate the cortical hemodynamic responses to swallowing across three head positions —chin-down, chin-neutral, and chin-up — using functional near-infrared spectroscopy (fNIRS) in the bilateral precentral and postcentral gyrus regions of interest. Twenty-six healthy adults completed 32 swallows of 5 ml water in each head position. Results revealed short-term cortical activation increases for chin-up swallows compared to both chin-neutral (mean difference = 1.2, SE = 0.18, p = .048) and chin-down swallows (mean difference = 0.76, SE = 0.18, p = .009). These findings suggest that postural changes during swallowing induce immediate neural adaptations in people without swallowing difficulty. These modifications likely reflect the necessary sensory and neuromuscular adaptations required for safe swallowing in different head positions, with less hyolaryngeal movement needed for a chin-down swallow and more movement needed for a chin-up swallow. While challenging swallow conditions, like the chin-up, may offer promising therapeutic potential, caution is warranted considering the associated safety risk, and further investigation is needed. This study provides insights into the immediate effects of head positions on cortical activity during swallowing and highlights avenues for future research in dysphagia rehabilitation.

A randomised crossover trial of nitrate and breakfast on prefrontal cognitive and haemodynamic response functions

It remains unknown whether dietary nitrate and breakfast may enhance working memory (WM) performance by augmenting physiological mechanisms and subjective psychological well-being. We performed a 3-arm randomised within-subject crossover study, with pretest-posttest comparisons, to test whether nitrate consumption via breakfast with a beetroot juice shot or regular breakfast compared to no breakfast improved WM (measured with n-back tests) and cognitive task-related changes in prefrontal cortical haemodynamic response (oxygenated- and deoxygenated-haemoglobin derived from functional near-infrared spectroscopy). In addition, effects on peripheral vascular function and self-reported psychological factors were assessed. In 60 adolescents (13–15 years old; 66% girls), WM improved in all conditions, with no intervention effects. Intervention effects were seen for oxygenated-haemoglobin changes, such that it increased after the breakfast with a nitrate shot during the WM tests and decreased after the regular breakfast. Thus, different neurophysiological mechanisms may be at play to preserve WM in adolescents depending on their breakfast composition. The trial was registered in the ISRCTN registry (ISRCTN16596056) on 21/02/2022.

Use of cortical hemodynamic responses in digital therapeutics for upper limb rehabilitation in patients with stroke

BackgroundStroke causes long-term disabilities, highlighting the need for innovative rehabilitation strategies for reducing residual impairments. This study explored the potential of functional near-infrared spectroscopy (fNIRS) for monitoring cortical activation during rehabilitation using digital therapeutics.MethodsThis cross-sectional study included 18 patients with chronic stroke, of whom 13 were men. The mean age of the patients was 67.0 ± 7.1 years. Motor function was evaluated through various tests, including the Fugl–Meyer assessment for upper extremity (FMA-UE), grip and pinch strength test, and box and block test. All the patients completed the digital rehabilitation program (MotoCog®, Cybermedic Co., Ltd., Republic of Korea) while being monitored using fNIRS (NIRScout®, NIRx Inc., Germany). Statistical parametric mapping (SPM) was employed to analyze the cortical activation patterns from the fNIRS data. Furthermore, the K-nearest neighbor (K-NN) algorithm was used to analyze task performance and fNIRS data to classify the severity of motor impairment.ResultsThe participants showed diverse task performances in the digital rehabilitation program, demonstrating distinct patterns of cortical activation that correlated with different motor function levels. Significant activation was observed in the ipsilesional primary motor area (M1), primary somatosensory area (S1), and contralateral prefrontal cortex. The activation patterns varied according to the FMA-UE scores. Positive correlations were observed between the FMA-UE scores and SPM t-values in the ipsilesional M1, whereas negative correlations were observed in the ipsilesional S1, frontal lobe, and parietal lobe. The incorporation of cortical hemodynamic responses with task scores in a digital rehabilitation program substantially improves the accuracy of the K-NN algorithm in classifying upper limb functional levels in patients with stroke. The accuracy for tasks, such as the gas stove-operation task, increased from 44.4% using only task scores to 83.3% when these scores were combined with oxy-Hb t-values from the ipsilesional M1.ConclusionsThe results advocated the development of tailored digital rehabilitation strategies by combining the behavioral and cerebral hemodynamic data of patients with stroke. This approach aligns with the evolving paradigm of personalized rehabilitation in stroke recovery, highlighting the need for further extensive research to optimize rehabilitation outcomes.

Disrupted hemodynamic response within dorsolateral prefrontal cortex during cognitive tasks among people with multiple sclerosis-related fatigue.

Mental fatigue is an early and enduring symptom in persons with autoimmune disease particularly multiple sclerosis (MS). Neuromodulation has emerged as a potential treatment although optimal cortical targets have yet to be determined. We aimed to examine cortical hemodynamic responses within bilateral dorsolateral prefrontal cortex (dlPFC) and frontopolar areas during single and dual cognitive tasks in persons with MS-related fatigue compared to matched controls. We recruited persons (15 MS and 12 age- and sex-matched controls) who did not have physical or cognitive impairment and were free from depressive symptoms. Functional near infrared spectroscopy (fNIRS) registered hemodynamic responses during the tasks. We calculated oxyhemoglobin peak, time-to-peak, coherence between channels (a potential marker of neurovascular coupling) and functional connectivity (z-score). In MS, dlPFC demonstrated disrupted hemodynamic coherence during both single and dual tasks, as evidenced by non-significant and negative correlations between fNIRS channels. In MS, reduced coherence occurred in left dorsolateral PFC during the single task but occurred bilaterally as the task became more challenging. Functional connectivity was lower during dual compared to single tasks in the right dorsolateral PFC in both groups. Lower z-score was related to greater feelings of fatigue. Peak and time-to-peak hemodynamic response did not differ between groups or tasks. Hemodynamic responses were inconsistent and disrupted in people with MS experiencing mental fatigue, which worsened as the task became more challenging. Our findings point to dlPFC, but not frontopolar areas, as a potential target for neuromodulation to treat cognitive fatigue.

Low frequency oscillations reflect neurovascular coupling and disappear after cerebral death

Spectrum power analysis in the low frequency oscillations (LFO) region of functional near infrared spectroscopy (fNIRS) is a promising method to deliver information about brain activation and therefore might be used for prognostication in patients with disorders of consciousness in the neurocritical care unit alongside with established methods. In this study, we measure the cortical hemodynamic response measured by fNIRS in the LFO region following auditory and somatosensory stimulation in healthy subjects. The significant hemodynamic reaction in the contralateral hemisphere correlation with the physiologic electric response suggests neurovascular coupling. In addition, we investigate power spectrum changes in steady state measurements of cerebral death patients and healthy subjects in the LFO region, the frequency of the heartbeat and respiration. The spectral power within the LFO region was lower in the patients with cerebral death compared to the healthy subjects, whereas there were no differences in spectral power for physiological activities such as heartbeat and respiration rate. This finding indicates the cerebral origin of our low frequency measurements. Therefore, LFO measurements are a potential method to detect brain activation in patients with disorders of consciousness and cerebral death. However, further studies in patients are needed to investigate its potential clinical use.

Reduced inhibition control ability in children with ADHD due to coexisting learning disorders: an fNIRS study.

Inhibition control, as the core component of executive function, might play a crucial role in the understanding of attention deficit/hyperactivity disorder (ADHD) and specific learning disorders (SLD). Inhibition control deficits have been observed in children with ADHD or SLD. This study sought to test in a multi-modal fashion (i.e., behavior and plus brain imaging) whether inhibition control abilities would be further deteriorated in the ADHD children due to the comorbidity of SLD. A total number of 90 children (aged 6-12 years) were recruited, including 30 ADHD, 30 ADHD+SLD (children with the comorbidity of ADHD and SLD), and 30 typically developing (TD) children. For each participant, a 44-channel functional near infrared spectroscopy (fNIRS) equipment was first adopted to capture behavioral and cortical hemodynamic responses during a two-choice Oddball task (a relatively new inhibition control paradigm). Then, 50 metrics were extracted, including 6 behavioral metrics (i.e., OddballACC, baselineACC, totalACC, OddballRT, baselineRT, and totalRT) and 44 beta values in 44 channels based on general linear model. Finally, differences in those 50 metrics among the TD, ADHD, and ADHD+SLD children were analyzed. Findings showed that: (1) OddballACC (i.e., the response accuracy in deviant stimuli) is the most sensitive metric in identifying the differences between the ADHD and ADHD+SLD children; and (2) The ADHD+SLD children exhibited decreased behavioral response accuracy and brain activation level in some channels (e.g., channel CH35) than both the ADHD and TD children. Findings seem to support that inhibition control abilities would be further decreased in the ADHD children due to the comorbidity of SLD.

Effects of rhythmic visual cues on cortical activation and functional connectivity features during stepping: an fNIRS study.

Rhythmic visual cues (RVCs) may influence gait initiation by modulating cognition resources. However, it is unknown how RVCs modulate cognitive resources allocation during gait movements. This study focused on investigating the effects of RVCs on cortical hemodynamic response features during stepping to evaluate the changes of cognitive resources. We recorded cerebral hemoglobin concentration changes of 14 channels in 17 healthy subjects using functional near-infrared spectroscopy (fNIRS) during stepping tasks under exposure to RVCs and non-rhythmic visual cues (NRVCs). We reported mean oxygenated hemoglobin (HbO) concentration changes, β-values, and functional connectivity (FC) between channels. The results showed that, the RVC conditions revealed lower HbO responses compared to the NRVC conditions during the preparation and early stepping. Correspondingly, the β-values reflected that RVCs elicited lower hemodynamic responses than NRVCs, and there was a decreasing trend in stimulus-evoked cortical activation as the task progressed. However, the FC between channels were stronger under RVCs than under NRVCs during the stepping progress, and there were more significant differences in FC during the early stepping. In conclusion, there were lower cognitive demand and stronger FC under RVC conditions than NRVC conditions, which indicated higher efficiency of cognitive resources allocation during stepping tasks. This study may provide a new insight for further understanding the mechanism on how RVCs alleviate freezing of gait.

Application of functional near-infrared spectroscopy (fNIRS) in tinnitus research: contemporary insights and perspectives.

Tinnitus, characterized by phantom sound perception, is a highly disruptive condition lacking clearly effective treatments. Its complex neural mechanisms are not fully elucidated. Functional near-infrared spectroscopy (fNIRS) is a promising neuroimaging tool well-suited for assessing tinnitus due to its quietness, portability, and ability to directly measure cortical hemodynamic responses. This study timely summarizes the recent applications of fNIRS in investigating tinnitus pathology, correlating neuroimaging biomarkers with symptom severity, and evaluating treatment efficacy. Further studies with larger samples are warranted to reproduce existing findings. Thus, fNIRS appears to be a promising tool in tinnitus research. Addressing technical limitations, optimizing control groups, advancing data analysis, integrating standardized, and individualized experimental protocols can facilitate the extended and robust utilization of fNIRS in tinnitus research.

Identification of the human cerebral cortical hemodynamic response to passive whole-body movements using near-infrared spectroscopy.

This study aimed to investigate the cerebral cortical response to naturalistic vestibular stimulation induced by real physical motion and to validate the vestibular cerebral cortex previously identified using alternative vestibular stimulation. Functional NIRS data were collected from 12 right-handed subjects when they were sitting in a motion platform that generated three types of whole-body passive translational motion (circular, lateral, and fore-and-aft). The study found that different cortical regions were activated by the three types of motion. The cortical response was more widespread under circular motion in two dimensions compared to lateral and fore-and-aft motions in one dimensions. Overall, the identified regions were consistent with the cortical areas found to be activated in previous brain imaging studies. The results provide new evidence of brain selectivity to different types of motion and validate previous findings on the vestibular cerebral cortex.

20 The Impact of Perceived Pain on Neural Efficiency During Walking in Older Adults

Objective:Pain is a mechanism for attention disruption due, in part, to a shared reliance on the prefrontal cortex (PFC). Amongst older adults, the experience of pain is both prevalent and functionally impactful. Dual-task walking (DTW) paradigms are a useful means of assessing the impact of pain on attentional control and known to be sensitive to changes in the cortical hemodynamic response within the PFC. To date, however, few studies have utilized such paradigms to examine the impact of self-reported pain on attentional control via assessment of cognitive, gait and neuroimaging outcomes. Examining these associations would facilitate a better understanding of the ways in which pain may negatively impact neural efficiency, thereby increasing risk of adverse functional outcomes, in healthy aging.Participants and Methods:Study participants (N= 408; mean age = 76 ± 6.5ys; % female =55.4) were grouped into pain (n= 266) and no pain (n= 142) groups based upon their responses on the MOS-PSS and MOS-PES. These questionnaires were also used to assess self-reported levels of pain severity and interference amongst individuals with reported pain. Functional near-infrared spectroscopy was used to measure intraindividual variability (IIV) of the cortical hemodynamic response within the PFC during a DTW paradigm which consisted of Single-Task-Walk (STW), Cognitive Interference (Alpha), and Dual-Task-Walk (DTW) conditions. Participants walked along an electronic walkway and quantitative gait data were extracted in order to assess IIV in stride length during STW and DTW conditions. The rate of correct letter generation was used as a measure of cognitive accuracy during Alpha and DTW conditions. Linear mixed effects models (LMEMs) were used to examine the effects of perceived pain on neural and behavioral responses as well as on the change in these outcomes form single- to dual-task conditions. Stratified LMEMs were used to examine whether these associations differed by gender.Results:LMEMs revealed that perceived pain presence was associated with reduced IIV in PFC oxygenation (estimate = -0.032, p = 0.037) and reduced IIV in stride length in the DTW condition (estimate = -1.180, p = 0.006). High pain severity was associated with a greater increase in stride length IIV from STW to DTW (estimate = -1.301, p = 0.039). Stratified LMEMs revealed that the association between pain and neural IIV was significant in only males (estimate = -0.049, p = 0.037), while the association between pain and gait IIV was significant in only females (estimate = -1.712, p = .008).Conclusions:Study results suggest that self-reported pain over one month is associated with differential patterns of neural and behavioral responding amongst healthy, community-dwelling older adults. Furthermore, it appears that males are more susceptible to the neural effects of pain, while females are more susceptible to the behavioral effects under attention-demanding conditions. In this population, these patterns may reflect a tendency towards inefficient neural and behavioral modifications in response to perceived pain. These findings highlight the need for clinical use of routine pain assessments and, when appropriate, the implementation of timely and effective pain treatments in aging.

Positive effects of brisk walking and Tai Chi on cognitive function in older adults: An fNIRS study

Exercise has shown to have beneficial effects on cognition in older adults. The purpose of this study was to investigate the cortical hemodynamic responses during the word-color Stroop test (WCST) prior and after acute walking and Tai Chi exercise by functional near-infrared spectroscopy (fNIRS). Twenty participants (9 males, mean age 62.8 ± 5.2), first underwent a baseline WCST test, after which they took three WCST tests in a randomized order, (a) after sitting rest (control), (b) after 6 minutes performing Tai Chi Quan, and (c) after a bout of 6 minutes brisk walking. During these four WCST tests cortical hemodynamic changes in the prefrontal area were monitored with fNIRS. Both brisk walking and Tai Chi enhanced hemodynamic activity during the Stroop incongruent tasks, leading to improved cognitive performance (quicker reaction time). Brisk walking induced a greater hemodynamic activity in the right dorsolateral prefrontal cortex (DLPFC) and ventrolateral prefrontal cortex (VLPFC) area, whereas Tai Chi induced a greater bilateral hemodynamic activity in the DLPFC and VLPFC areas. The present study provided empirical evidence of enhanced hemodynamic response in task- specific regions of the brain that can be achieved by a mere six minutes of brisk walking or Tai Chi in older adults.

Modulation Of Cortical Hemodynamic Responses During The Craniocervical Flexion Test In Individuals With Post-traumatic Headache

Modulation Of Cortical Hemodynamic Responses During The Craniocervical Flexion Test In Individuals With Post-traumatic Headache

Functional Near-Infrared Spectroscopy of English-Speaking Adults With Attention-Deficit/Hyperactivity Disorder During a Verbal Fluency Task

Objective: Functional near-infrared spectroscopy (fNIRS) provides direct and quantitative assessment of cortical hemodynamic response. It has been used to identify neurophysiological alterations in medication-naïve adults with attention-deficit/hyperactivity disorder (ADHD). Hence, this study aimed to distinguish both medication-naïve and medicated adults with ADHD from healthy controls (HC). Method: 75 HCs, 75 medication-naïve, and 45 medicated patients took part in this study. fNIRS signals during a verbal fluency task (VFT) were acquired using a 52-channel system and relative oxy-hemoglobin changes in the prefrontal cortex were quantified. Results: Prefrontal cortex hemodynamic response was lower in patients than HCs (p ≤ ≤.001). Medication-naïve and medicated patients did not differ in hemodynamic response or symptom severity (p > .05). fNIRS measurements were not associated with any clinical variables (p > .05). 75.8% patients and 76% HCs were correctly classified using hemodynamic response. Conclusion: fNIRS may be a potential diagnostic tool for adult ADHD. These findings need to be replicated in larger validation studies.

A Potential Biomarker of Brain Activity in Autism Spectrum Disorders: A Pilot fNIRS Study in Female Preschoolers

Autism spectrum disorder (ASD) refers to a neurodevelopmental condition whose detection still remains challenging in young females due to the heterogeneity of the behavioral phenotype and the capacity of camouflage. The availability of quantitative biomarkers to assess brain function may support in the assessment of ASD. Functional Near-infrared Spectroscopy (fNIRS) is a non-invasive and flexible tool that quantifies cortical hemodynamic responses (HDR) that can be easily employed to describe brain activity. Since the study of the visual phenotype is a paradigmatic model to evaluate cerebral processing in many neurodevelopmental conditions, we hypothesized that visually-evoked HDR (vHDR) might represent a potential biomarker in ASD females. We performed a case-control study comparing vHDR in a cohort of high-functioning preschooler females with ASD (fASD) and sex/age matched peers. We demonstrated the feasibility of visual fNIRS measurements in fASD, and the possibility to discriminate between fASD and typical subjects using different signal features, such as the amplitude and lateralization of vHDR. Moreover, the level of response lateralization was correlated to the severity of autistic traits. These results corroborate the cruciality of sensory symptoms in ASD, paving the way for the validation of the fNIRS analytical tool for diagnosis and treatment outcome monitoring in the ASD population.

Scalable, modular continuous wave functional near-infrared spectroscopy system (Spotlight).

We present a fiberless, portable, and modular continuous wave-functional near-infrared spectroscopy system, Spotlight, consisting of multiple palm-sized modules-each containing high-density light-emitting diode and silicon photomultiplier detector arrays embedded in a flexible membrane that facilitates optode coupling to scalp curvature. Spotlight's goal is to be a more portable, accessible, and powerful functional near-infrared spectroscopy (fNIRS) device for neuroscience and brain-computer interface (BCI) applications. We hope that the Spotlight designs we share here can spur more advances in fNIRS technology and better enable future non-invasive neuroscience and BCI research. We report sensor characteristics in system validation on phantoms and motor cortical hemodynamic responses in a human finger-tapping experiment, where subjects wore custom 3D-printed caps with two sensor modules. The task conditions can be decoded offline with a median accuracy of 69.6%, reaching 94.7% for the best subject, and at a comparable accuracy in real time for a subset of subjects. We quantified how well the custom caps fitted to each subject and observed that better fit leads to more observed task-dependent hemodynamic response and better decoding accuracy. The advances presented here should serve to make fNIRS more accessible for BCI applications.

Cortical haemodynamic responses predict individual ability to recognise vocal emotions with uninformative pitch cues but do not distinguish different emotions.

We investigated the cortical representation of emotional prosody in normal-hearing listeners using functional near-infrared spectroscopy (fNIRS) and behavioural assessments. Consistent with previous reports, listeners relied most heavily on F0 cues when recognizing emotion cues; performance was relatively poor-and highly variable between listeners-when only intensity and speech-rate cues were available. Using fNIRS to image cortical activity to speech utterances containing natural and reduced prosodic cues, we found right superior temporal gyrus (STG) to be most sensitive to emotional prosody, but no emotion-specific cortical activations, suggesting that while fNIRS might be suited to investigating cortical mechanisms supporting speech processing it is less suited to investigating cortical haemodynamic responses to individual vocal emotions. Manipulating emotional speech to render F0 cues less informative, we found the amplitude of the haemodynamic response in right STG to be significantly correlated with listeners' abilities to recognise vocal emotions with uninformative F0 cues. Specifically, listeners more able to assign emotions to speech with degraded F0 cues showed lower haemodynamic responses to these degraded signals. This suggests a potential objective measure of behavioural sensitivity to vocal emotions that might benefit neurodiverse populations less sensitive to emotional prosody or hearing-impaired listeners, many of whom rely on listening technologies such as hearing aids and cochlear implants-neither of which restore, and often further degrade, the F0 cues essential to parsing emotional prosody conveyed in speech.

The assessment of cortical hemodynamic responses induced by tubuloglomerular feedback using in vivo imaging.

The tubuloglomerular feedback (TGF) mechanism modulates renal hemodynamics and glomerular filtration rate in individual nephrons. Our study aimed to evaluate the TGF-induced vascular responses by inhibiting Na-K-2Cl co-transporters and sodium-glucose co-transporters in rats. We assessed cortical hemodynamics with high-resolution laser speckle contrast imaging, which enabled the evaluation of blood flow in individual microvessels and analysis of their dynamical patterns in the time-frequency domain. We demonstrated that a systemic administration of furosemide abolishes TGF-mediated hemodynamic responses. Furthermore, we showed that the local microcirculatory blood flow decreased, and the TGF-induced hemodynamic oscillations were sustained but weakened after inhibiting sodium-glucose co-transporters in Sprague-Dawley rats.

Cortical hemodynamic response during cognitive Stroop test in acute stroke patients assessed by fNIRS.

Following acute ischemic stroke (AIS) many patients experience cognitive impairment which interferes neurorehabilitation. Understanding and monitoring pathophysiologic processes behind cognitive symptoms requires accessible methods during testing and training. Functional near-infrared spectroscopy (fNIRS) can assess activational hemodynamic responses in the prefrontal cortex (PFC) and feasibly be used as a biomarker to support stroke rehabilitation. Exploring the feasibility of fNIRS as a biomarker during the Stroop Color and Word Test (SCWT) assessing executive function in AIS patients. Observational study of 21 patients with mild to moderate AIS and 22 healthy age- and sex-matched controls (HC) examined with fNIRS of PFC during the SCWT. Hemodynamic responses were analyzed with general linear modeling. The SCWT was performed worse by AIS patients than HC. Neither patients nor HC showed PFC activation, but an inverse activational pattern primarily in superolateral and superomedial PFC significantly lower in AIS. Hemodynamic responses were incoherent to test difficulty and performance. No other group differences or lateralization were found. AIS patients had impaired executive function assessed by the SCWT, while both groups showed an inverse hemodynamic response significantly larger in HC. Investigations assessing the physiology behind inverse hemodynamic responses are warranted before deeming clinical implementation reasonable.