Near-infrared Spectroscopy Responses Research Articles

Effects of green tea and roasted green tea on human responses

Our objective was to elucidate the effects of tea consumption on refreshment and stress reduction/recovery through examining the multiple associations among factors such as various physiological responses and task performance. Participants included 20 healthy young men who performed a mental arithmetic task while 11 physiological responses were measured. The experiments were conducted twice under different beverage consumption conditions on separate days. The mental arithmetic task was executed six times in 1 day; participants ingested hot water, green tea, or roasted green tea (hojicha) before each task. Several subjective assessments: subjective fatigue, stress, mental workload, and flow were evaluated after each task. The R–R intervals, heart rate variability spectral components, the Poincaré plot indices (SD1 and SD2) and plethysmogram amplitude tended to decrease during task periods compared to resting periods. Tissue blood volume/flow (TBV, TBF) and near-infrared spectroscopy responses (NIRS) were lower in the tea condition than in the hot water condition. By scrutinizing various indicators, we found that aromatic stimulation of Japanese tea beverages has the potential to induce positive effects, enhance mental task performance, promote refreshment, and alleviate feelings of fatigue. These positive effects were observed even in small quantities and within a short duration, mirroring responses observed in daily consumption.

Longitudinal Characterization of Hemodynamic Changes with Multimodal Optical Techniques in Patients with Sickle Cell Disease Treated with Mitapivat

The physiological impacts of sickle cell disease (SCD) are widespread and severe if left untreated. Sickled RBCs initiate vaso-occlusion (VOC) and have altered biomechanical properties that negatively affect blood rheology and microvascular hemodynamics in patients with SCD. Therapeutics can target different mechanistic pathways including reduction of hemoglobin S (HbS) polymerization, oxidative stress, or inflammation. There is an unmet need for non-invasive, point-of-care technologies that characterize the microvascular hemodynamics in SCD which could potentially broaden understanding of the underlying pathophysiology and supplement a clinician's ability to monitor therapeutic changes. Current clinical approaches can be time- and resource- intensive which limit their accessibility. Near-infrared spectroscopy (NIRS) is a non-invasive, optical technique that quantifies microvascular hemodynamics including hemoglobin (Hb) concentration, tissue oxygen saturation (StO 2), and blood flow (Cerussi et al, 2005). We evaluate the sensitivity of NIRS technologies to hemodynamic changes in patients with SCD undergoing treatment with mitapivat, an investigational oral allosteric activator of pyruvate kinase (PK), and compare the optical changes to changes in standard hematology markers with regard to the initial response and consistency of the response over time. Fifteen patientswith HbSSwere enrolled in a study (ClinicalTrials.gov, NCT04610866) evaluating the long-term safety and tolerability of mitapivat in patients with SCD. We performed an optical hemodynamic assessment for each patient for a total of eight study visits over the span of a year including at baseline prior to drug initiation. NIRS probes were affixed to the forearm and forehead to collect hemodynamic information characteristic of brain and skeletal muscle while performing a brachial cuff occlusion challenge. We quantified concentration of oxy- and deoxy- Hb as well as StO 2 during the resting baseline prior to the occlusion. Additionally, we analyzed the post-occlusion reactive hyperemic response to assess vascular reactivity. Analysis was focused on quantifying the degree of change due to mitapivat treatment as well as the consistency of the response over the course of a year. Optical metrics were first compared against changes in Hb (Quang et, 2022) and then evaluated for consistency throughout the rest of the study period. Nine out of 15 patients were assessed as baseline NIRS data were not available for six patients.We calculated optical hemodynamic metrics for all 72 measurement visits; two visits were excluded due to poor NIRS data quality. Figure 1A shows a typical measurement setup with NIRS probes acquiring simultaneous measurements from the forehead and forearm. Figure 1B compares the mean Hb level, mean forehead StO 2, and mean forearm StO 2 across the first year of treatment. Over the first six months, we observed an increase in forehead StO 2 from 56% to 60% and forearm StO 2 from 59% to 63%; blood Hb levels exhibited a similar increase going from 8.5 g/dL to 9.8 g/dL; this increase was sustained over the second six months for all three parameters. Average forehead StO 2 remained +3.6% above baseline while forearm StO 2 remained +1.7% above baseline at the end of a year. NIRS can non-invasively provide objective measures of tissue composition, metabolism and vascular reactivity and can be performed in a simple manner with a series of simple perturbations.In this limited dataset, we have demonstrated that NIRS appears to reflect changes in Hb related to mitapivat both in response to an acute change and over an extended period. Furthermore, we observed that on average, the NIRS responses were consistently elevated throughout the course of the year, mirroring what was observed in the blood Hb levels. Hemodynamic changes appear to be more easily observed in the brain rather than the skeletal muscle. Our data suggest that NIRS could be an adjunct for non-invasive hemodynamic monitoring in patients with SCD undergoing treatment.

Measurements of the lateral cerebellar hemispheres using near-infrared spectroscopy through comparison between autism spectrum disorder and typical development

The cerebellum plays a vital role in cognition, communication with the cerebral cortex, and fine motor coordination. Near-infrared spectroscopy (NIRS) is a portable, less restrictive, and noninvasive functional brain imaging method that can capture brain activity during movements by measuring the relative oxyhemoglobin (oxy-Hb) concentrations in the blood. However, the feasibility of using NIRS to measure cerebellar activity requires discussion. We compared NIRS responses between areas assumed to be the cerebellum and the occipital lobe during a fine motor task (tying a bow knot) and a visual task. Our results showed that the oxy-Hb concentration increased more in the occipital lobe than in the cerebellum during the visual task (p =.034). In contrast, during the fine motor task, the oxy-Hb concentration decreased in the occipital lobe but increased significantly in the cerebellum, indicating a notable difference (p =.015). These findings suggest that we successfully captured cerebellar activity associated with processing, particularly fine motor coordination. Moreover, the observed responses did not differ between individuals with autism spectrum disorder and those with typical development. Our study demonstrates the meaningful utility of NIRS as a method for measuring cerebellar activity during movements.

Brain BOLD and NIRS response to hyperoxic challenge in sickle cell disease and chronic anemias

PurposeCongenital anemias, including sickle cell anemia and thalassemia, are associated with cerebral tissue hypoxia and heightened stroke risks. Recent works in sickle cell disease mouse models have suggested that hyperoxia respiratory challenges can identify regions of the brain having chronic tissue hypoxia. Therefore, this work investigated differences in hyperoxic response and regional cerebral oxygenation between anemic and healthy subjects. MethodsA cohort of 38 sickle cell disease subjects (age 22 ± 8 years, female 39%), 25 non-sickle anemic subjects (age 25 ± 11 years, female 52%), and 31 healthy controls (age 25 ± 10 years, female 68%) were examined. A hyperoxic gas challenge was performed with concurrent acquisition of blood oxygen level-dependent (BOLD) MRI and near-infrared spectroscopy (NIRS). In addition to hyperoxia-induced changes in BOLD and NIRS, global measurements of cerebral blood flow, oxygen delivery, and cerebral metabolic rate of oxygen were obtained and compared between the three groups. ResultsRegional BOLD changes were not able to identify brain regions of flow limitation in chronically anemic patients. Higher blood oxygen content and tissue oxygenation were observed during hyperoxia gas challenge. Both control and anemic groups demonstrated lower blood flow, oxygen delivery, and metabolic rate compared to baseline, but the oxygen metabolism in anemic subjects were abnormally low during hyperoxic exposure. ConclusionThese results indicated that hyperoxic respiratory challenge could not be used to identify chronically ischemic brain. Furthermore, the low hyperoxia-induced metabolic rate suggested potential negative effects of prolonged oxygen therapy and required further studies to evaluate the risk for hyperoxia-induced oxygen toxicity and cerebral dysfunction.

Alterations in tissue oxygen saturation measured by near-infrared spectroscopy in trauma patients after initial resuscitation are associated with occult shock

PurposePersistent occult hypoperfusion after initial resuscitation is strongly associated with increased morbidity and mortality after severe trauma. The objective of this study was to analyze regional tissue oxygenation, along with other global markers, as potential detectors of occult shock in otherwise hemodynamically stable trauma patients.MethodsTrauma patients undergoing active resuscitation were evaluated 8 h after hospital admission with the measurement of several global and local hemodynamic/metabolic parameters. Apparently hemodynamically stable (AHD) patients, defined as having SBP ≥ 90 mmHg, HR < 100 bpm and no vasopressor support, were followed for 48 h, and finally classified according to the need for further treatment for persistent bleeding (defined as requiring additional red blood cell transfusion), initiation of vasopressors and/or bleeding control with surgery and/or angioembolization. Patients were labeled as “Occult shock” (OS) if they required any intervention or “Truly hemodynamically stable” (THD) if they did not. Regional tissue oxygenation (rSO2) was measured non-invasively by near-infrared spectroscopy (NIRS) on the forearm. A vascular occlusion test was performed, allowing a 3-min deoxygenation period and a reoxygenation period following occlusion release. Minimal rSO2 (rSO2min), Delta-down (rSO2–rSO2min), maximal rSO2 following cuff-release (rSO2max), and Delta-up (rSO2max–rSO2min) were computed. The NIRS response to the occlusion test was also measured in a control group of healthy volunteers.ResultsSixty-six consecutive trauma patients were included. After 8 h, 17 patients were classified as AHD, of whom five were finally considered to have OS and 12 THD. No hemodynamic, metabolic or coagulopathic differences were observed between the two groups, while NIRS-derived parameters showed statistically significant differences in Delta-down, rSO2min, and Delta-up.ConclusionsAfter 8 h of care, NIRS evaluation with an occlusion test is helpful for identifying occult shock in apparently hemodynamically stable patients.Level of evidenceIV, descriptive observational study.Trial registrationClinicalTrials.gov Registration Number: NCT02772653.

Mechanomyography and tissue oxygen saturation during electrically-evoked wrist extensor fatigue in people with tetraplegia.

Repetitive electrically-evoked muscle contractions lead to the early onset of muscle fatigue. This study assessed the relationship between muscle mechanomyography (%RMS-MMG) and tissue oxygen saturation (%TSI) in extensor carpi radialis (ECR) during electrically-evoked fatiguing exercise in individuals with tetraplegia. Skin-surface mechanomyography (MMG) and near-infrared spectroscopy (NIRS) sensors were placed on the ECR of seven individuals with tetraplegia. All participants performed repetitive electrically-evoked wrist extension to fatigue while their muscle MMG and NIRS responses were monitored against their power output (PO). One out of seven participants showed no changes in %TSI throughout the repeated wrist FES-evoked contraction. The other six participants' %TSI was positively correlated with %PO before fatigue onset. At 50%POpeak , %TSI was negatively correlated (0.489) significantly with declining %PO as the ability of the muscle to take up oxygen became limited. The %RMS-MMG behaved analogously during pre and post-fatigue against declining %PO, whereby both displayed positive correlations of 0.443 and 0.214, respectively, (%RMS-MMG decreased) throughout the exercise session. Regression analysis revealed that %TSI was proportional to pre-fatigue and inversely proportional to %RMS-MMG during post-fatigue. The significant changes in muscle mechanomyography and tissue oxygenation correlations after 50%POpeak implied that the muscle contraction mechanical-and-physiological behavior association had been altered following FES-evoked fatigue.

ESTIMATION OF THE VENTILATORY THRESHOLD USING WIRELESS NEAR-INFRARED SPECTROSCOPY AND DISTACE MAXIMUM ANALYSIS

The ventilatory threshold (VT) separates moderate intensity (<VT) and heavy intensity (>VT) domains and can be determined using a pulmonary gas exchange system in a laboratory setting. Knowledge of an exercise workload (i.e., velocity during running) in which the VT occurs is useful when prescribing individualized cardiorespiratory exercise. If wireless near-infrared spectroscopy (NIRS) systems could estimate the VT, more environment specific testing results could be obtained. PURPOSE: To investigate if the VT can be estimated via wireless NIRS responses from the medial gastrocnemius (G) or vastus lateralis (VL) during a running graded exercise test (GXT). METHODS: 17 healthy, recreationally active adults (age = 21 ± 4 years, height = 1.68 ± 0.11 m, weight = 66.3 ± 16.8 kg) completed a GXT on a treadmill to volitional fatigue. Every three minutes the velocity was increased by +1 km/hr (starting velocity = 5 km/hr) while the incline remained at 1%. Pulmonary gas exchange and NIRS (G, VL) data were continuously collected. The pulmonary gas exchange data was visually inspected (V-Slope, end-tidal pressures, and ventilatory equivalents) to identify the velocity at which the VT occurred (vVT). The last 15 seconds of NIRS data (G, VL) for each stage were averaged and the velocity at each NIRS threshold (vNIRS-G, vNIRS-VL) were determined by the distance maximum (Dmax) analysis. Concurrent validity of the NIRS thresholds (vNIRS-G, vNIRS-VL) were assessed against the VT (vVT) using Pearson correlation coefficients (r) and standard error of estimate (SEE). Statistical significance was established a priori at p < 0.05. RESULTS: vNIRS-G was not significantly related to vVT (vNIRS-G = 8.6 ± 1.2 km/hr, vVT = 8.1 ± 1.1 km/hr, r = -0.08, p = 0.769) and had an SEE of 1.2 km/hr. vNIRS-VL also was not significantly related to vVT (vNIRS-VL = 9.1 ± 1.6 km/hr, r = 0.313, p = 0.221) and had an SEE of 1.1 km/hr. CONCLUSION: The present results demonstrate poor concurrent validity between the NIRS thresholds and the VT during running exercise. Based upon the present results, it is suggested that the NIRS threshold not be determined by Dmax analysis during running GXT.

Quantitative assessment of near-infrared spectroscopy time course under hypercapnia using an a priori model-based fitting

Background: Partial arterial pressure of carbon dioxide (CO2) modulates cerebral blood flow through a vasoreactivity mechanism. Near infrared spectroscopy (NIRS) can be used to record these changes in cerebral hemodynamics. However, no laterality comparison of the NIRS signal has been performed despite being a prerequisite for the use of such a method in a vasoreactivity monitoring context. We propose to investigate the NIRS signal laterality in response to a CO2-inhalation-based hypercapnia paradigm in healthy volunteers.Methods: Eleven healthy volunteers (6 women, 5 men, mean age: 31 ± 11) underwent a 3-block-design inhalation paradigm: normoxia (5min, “baseline”) – hypercapnia (2min, “stimulation”) – normoxia (5min, “post-stimulation”). NIRS signal was measured using a two-channel oximeter (INVOS 5100C, Medtronic, USA) with sensors placed symmetrically on both left and right sides on each subject’s forehead. Additional heart rate (HR) monitoring was performed simultaneously. Based on the NIRS mean signal pattern, an a priori model of parametric identification was applied for each channel to quantify parameters of interest (amplitude, time delay, excitation and post-stimulation time) for each inhalation block.Results: HR increased significantly during the stimulation block. The quality of the model was satisfactory: mean absolute errors between modeled and experimental signals were lower than the resolution of the device. No significant lateralization was found between left and right values of most of the parameters.Conclusion: Due to the lack of lateralization, this parametric identification of NIRS responses to hypercapnia could bring light to a potential asymmetry and be used as a biomarker in patients with cerebrovascular diseases.

Clinical Pearls

The hospital should be a safe, healing and humane environment for both patients and health care providers. However, pressures from growing patient acuity, operational constraints, increasing regulatory demands, and communication and staffing issues can diminish the quality of the work environment.Connor and colleagues evaluated the use of the AACN Healthy Work Environment (HWE) Tool with interdisciplinary staff and found thatIt is critical for health care system leaders to actively evaluate work environments to provide optimal patient outcomes. The authors recommend using the HWE tool as an organizational measure to identify substandard behaviors that may affect patients’ outcomes.See Article, pp 363–371The leading cause of patient safety incidents in the hospital is communication errors. In particular, postoperative team handover interactions are often written, unstructured, and not done face-to-face, increasing the chance of miscommunication that could lead to unfavorable patient outcomes.Turner and colleagues evaluated the use of (1) a handover checklist for postoperative patients admitted to the intensive care unit (ICU), and (2) a 5-item daily communication tool After implementation, they surveyed health care professionals and found a significant improvement inFour key areas for improving future communication were noted:The authors recommend simple, fillable, daily tools for improving communication in the ICU.See Article, pp 392–397Congenital heart disease (CHD) is the leading birth defect in the United States, with approximately 25% of affected neonates requiring major surgery in the first year of life. The risk of developmental delay and neurological deficits can be costly and increases the need for long-term health care services, some continuing into adulthood.Tran and colleagues used near infrared spectroscopy (NIRS) to measure regional cerebral oxygenation saturation as a noninvasive, surrogate measure of cerebral blood flow. They hypothesized that a weaker NIRS response to a posture-change blood pressure challenge would correlate with neurodevelopmental impairments. They found the following:The authors recommend close monitoring and early screening in neonates with CHD for timely implementation of appropriate interventions to prevent neurodevelopmental delays.See Article, pp 410–416More than half of all patients in the intensive care unit (ICU) are older adults, and many experience poor outcomes and decreased quality of life after hospitalization. Although organizations such as the Society of Critical Care Medicine have established guidelines to improve care and reduce post-intensive care syndrome, most guidelines are aimed at the general adult population and not at geriatric patients.Sinvani and colleagues examined the relationship between nonadherence and 6 geriatric-focused indicators and clinical outcomes in older ICU survivors. They found thatStandardized guidelines and care bundles have increased awareness of quality and safety in ICU care, but a gap remains in the implementation of geriatric-focused interventions. The authors recommend development and implementation of multicomponent solutions for use in ICUs.See Article, pp 354–361

Prefrontal and muscle oxygenation responses to supraventricular tachycardia

Supraventricular tachycardia (SVT) causes hypotension and cerebral hypoperfusion leading to syncope at times. The cerebral and peripheral vascular systems probably operate to maintain cerebral oxygenation against SVT‐induced hypoperfusion. However, time courses of cerebral and peripheral oxygenation responses to SVT has not been fully understood. The aim of this study was to examine the time course and relationship between cerebral and peripheral oxygenation responses and SVT‐induced hypotension. Prefrontal and forearm tissue oxygen index (TOI) and normalized tissue hemoglobin index (nTHI) were collected by near‐infrared spectroscopy (NIRS) during electrophysiological study (EPS) in 14 patients (55 ± 4 years old, 9 men) with SVT. AP decreased during 2–20 s of SVT. The prefrontal TOI and nTHI began to decrease (P &lt; 0.05) transiently at 6 s of SVT and then returned to the baseline level from 14 s. The initial decrease of prefrontal TOI appears to occur when hypotension was over approximately 20 mmHg. In contrast, the forearm TOI and nTHI decreased continuously from 11 s (P &lt; 0.05). The AP and prefrontal NIRS responses suggest that SVT‐induced great hypotension (&gt;20 mmHg) caused the transient reduction of cerebral oxygenation and blood volume, which may be followed by a recovering process owing to cerebral vasodilatation. The continuous reductions of forearm TOI and nTHI during SVT suggest restriction of muscle blood flow by vasoconstriction, which may contribute to redistribution of the blood to the brain.Support or Funding InformationThis research is supported by Automotive and Medical Concert Consortium (AMECC).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Combined surface electromyography, near-infrared spectroscopy and acceleration recordings of muscle contraction: The effect of motion

Noninvasive techniques, surface electromyography (sEMG) in particular, are being increasingly employed for assessing muscle activity. In these studies, local oxygen consumption and muscle metabolism are of great interest. Measurements can be performed noninvasively using optics-based methods such as near-infrared spectroscopy (NIRS). By combining energy consumption data provided by NIRS with muscle level activation data from sEMG, we may gain an insight into the metabolic and functional characteristics of muscle tissue. However, muscle motion may induce artifacts into EMG and NIRS. Thus, the inclusion of simultaneous motion measurements using accelerometers (ACMs) enhances possibilities to perceive the effects of motion on NIRS and EMG signals. This paper reviews the current state of noninvasive EMG and NIRS-based methods used to study muscle function. In addition, we built a combined sEMG/NIRS/ACM sensor to perform simultaneous measurements for static and dynamic exercises of a biceps brachii muscle. Further, we discuss the effect of muscle motion in response of NIRS and EMG when measured noninvasively. Based on our preliminary studies, both NIRS and EMG supply specific information on muscle activation, but their signal responses also showed similarities with acceleration signals which, in this case, were supposed to be solely sensitive to motions.

Hemodynamic Changes Associated with Interictal Spikes Induced by Acute Models of Focal Epilepsy in Rats: A Simultaneous Electrocorticography and Near-Infrared Spectroscopy Study.

Interictal spikes can be generated by blocking GABAA receptor-mediated inhibition. The nature of the hemodynamic activities associated with interictal spikes in acute models of focal epilepsy based on GABA deactivation has not been determined. We analyzed systemic changes in hemodynamic signals associated with interictal spikes generated by acute models of focal epilepsy. Simultaneous ElectroCorticoGraphy (ECoG) and Near-InfraRed Spectroscopy (NIRS) recordings were obtained in vivo from adult Sprague-Dawley rat brain during semi-periodic focal interictal spikes induced by local cortical application of low doses of Penicillin G (PG) and Bicuculline Methiodide (BM) as GABA deactivation agents. The Finite Impulse Response deconvolution technique was used to estimate the profile of hemodynamic changes in oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) concentrations associated with interictal ECoG spikes in each rat. Our results show that, in both acute models of focal epilepsy, the hemodynamic changes associated with interictal spikes were characterized by pre-spike and post-spike primary NIRS responses, and recovery periods with slight differences in amplitude and latency. The pre-spike period starting at least 2s prior to the onset of ECoG spikes was characterized by a significant decrease in HbO concomitant with an increase in HbR with respect to baseline. The post-spike primary NIRS response exhibited the expected changes described according to the classical view of neurovascular coupling, i.e., a significant increase in HbO and a significant decrease in HbR in response to interictal spikes. The recovery period was characterized by a decreased HbO signal and an increased HbR signal, followed by a return to baseline. Compared to the BM epilepsy model, the PG model was more stable and showed lower variability in the shape, amplitude and latency of the components of spike-related hemodynamic changes. Our findings support a prominent role for pre-spike hemodynamic changes in the initiation of interictal spikes. The mechanism of interactions between neuronal and vascular networks during the pre-spike period constitutes a complex process, resulting in increased sensitivity of the epileptogenic focus to induce neuronal spiking.

Cerebral haemodynamic response to somatosensory stimulation in near-term fetal sheep.

Cerebral haemodynamic response to neural stimulation has been extensively investigated in animal and clinical studies, in both adult and paediatric populations, but little is known about cerebral haemodynamic functional response in the fetal brain. The present study describes the cerebral haemodynamic response measured by near-infrared spectroscopy to somatosensory stimulation in fetal sheep. The cerebral haemodynamic response in the fetal sheep brain changes from a positive (increase in oxyhaemoglobin (oxyHb)) response pattern to a negative or biphasic response pattern when the duration of somatosensory stimulation is increased, probably due to cerebral vasoconstriction with prolonged stimulations. In contrast to adult studies, we have found that changes in fetal cerebral blood flow and oxyHb are positively increased in response to somatosensory stimulation during hypercapnia. We propose this is related to reduced vascular resistance and recruitment of cerebral vasculature in the fetal brain during hypercapnia. Functional hyperaemia induced by a localised increase in neuronal activity has been suggested to occur in the fetal brain owing to a positive blood oxygen level-dependent (BOLD) signal recorded by functional magnetic resonance imaging following acoustic stimulation. To study the effect of somatosensory input on local cerebral perfusion we used near-infrared spectroscopy (NIRS) in anaesthetised, partially exteriorised fetal sheep where the median nerve was stimulated with trains of pulses (2ms, 3.3Hz) for durations of 1.8, 4.8 and 7.8s. Signal averaging of cerebral NIRS responses to 20 stimulus trains repeated every 60s revealed that a short duration of stimulation (1.8s) increased oxyhaemoglobin in the contralateral cortex consistent with a positive functional response, whereas longer durations of stimulation (4.8, 7.8s) produced more variable oxyhaemoglobin responses including positive, negative and biphasic patterns of change. Mean arterial blood pressure and cerebral perfusion as monitored by laser Doppler flowmetry always showed small, but coincident increases following median nerve stimulation regardless of the type of response detected by the NIRS in the contralateral cortex. Hypercapnia significantly increased the baseline total haemoglobin and deoxyhaemoglobin, and in 7 of 8 fetal sheep positively increased the changes in contralateral total haemoglobin and oxyhaemoglobin in response to the 7.8s stimulus train, compared to the response recorded during normocapnia. These results show that activity-driven changes in cerebral perfusion and oxygen delivery are present in the fetal brain, and persist even during periods of hypercapnia-induced cerebral vasodilatation.

Changes in Brain Oxygenation in Response to Inhaled 100% Oxygen Are Different in Sickle Cell Disease Patients

Introduction: The prevalence of silent stroke increases monotonically with age in SCD patients, with more than 50% developing detectable white matter hyperintensities on MRI by adulthood. We are exploring the use of inhaled oxygen as a contrast agent to try to identify individuals at risk for silent stroke and to better understand how the brain regulates its own oxygen delivery. In this study, we report changes of brain Blood Oxygen Level Dependent (BOLD) signal and frontal Near Infrared Spectroscopy (NIRs) to 5 minutes of inhaled 100% oxygen in patients with sickle cell disease (SCD), non sickle anemia (ACTL), and control subjects.Method: The study was approved by the institutional review board and performed at Children’s Hospital Los Angeles (CHLA); all patients provided informed consent. Patients with previous stroke, pregnancy, and acute chest pain and crisis hospitalization within one month were excluded. 19 SCD patients (age = 20.7 ± 8.8), 12 patients with non sickle anemia syndromes (age = 25.1 ± 6.9) and 20 ethnicity matched control (CTL) subjects (age = 30.5 ± 12.7) were studied. Peripheral oxygen saturation (SpO2%) was measured by MRI compatible pulse oximeter. A five minute BOLD sequence was acquired with the patient breathing room air for 50 seconds, followed by 100% oxygen for 250 seconds. NIRS recordings of oxygenated hemoglobin change (DOHB), deoxygenated hemoglobin change (DDHB) and tissue oxygenation index (TOI) were recorded from the patient’s forehead. Average BOLD signal was from a 6 cm slab in the middle of the brain. CBC, hemoglobin electrophoresis, and markers of hemolysis were also measured.Results: A representative frontal DOHB signal, and the parameters used to characterize its time-course, are shown in Figure 1. DOHB remained stable until oxygen was administered and then increased over several minutes to a maximum. In many patients, the DOHB signal subsequently declined back toward baseline, representing the effects of compensatory cerebral vasoconstriction. The delay time was shorter in anemic subjects because of increased cerebral blood flow, but the rise times were not different. Peak DOHB increase was greater in SCD patients than in ACTL or non anemic control subjects (1.4 mM ± 0.2mM, 0.8 mM ± 0.2 mM and 0.6 mM ± 0.4 mM, respectively, p <0.0001 by ANOVA). There was no difference in the DOHB vasoconstriction response among the three patient groups.DOHB was highly correlated with DDHB and DTOI in all three patient groups. Consequently, both DDHB and DTOI changes were also larger in SCD patients. All three NIRs signal changes were larger in non-transfused SCD patients than in patients on chronic transfusions. Non-transfused SCD patients had more significant increases in SpO2% than chronically transfused subjects and the effect was proportional to hemoglobin F%, suggesting a p50 effect. After controlling for SpO2%, SCD patients still exhibited larger NIRs changes than ACTL or CTL patients, but the differences between transfused and non transfused SCD patients disappeared.Whole brain %BOLD was also correlated with changes in DOHB, DDHB, TOI, and SpO2%. The relationship between DOHB versus %BOLD is illustrated in Figure 2. %BOLD changes were also significantly higher in SCD patients. However, unlike the NIRS changes, whole brain %BOLD differences could entirely be explained by differences in SpO2% with hyperoxia.Conclusion:100% oxygen administration increases brain oxygenation in SCD patients to a greater degree than in control subjects or patients with anemia of other etiologies. Some of the differences can be explained by differences in resting oxygen saturations but disparities between BOLD and NIRs response suggest regional variation of brain oxygenation in response to this challenge. [Display omitted] [Display omitted] DisclosuresWood:Apopharma: Consultancy; AMAG: Consultancy; World Care Clinical: Consultancy; AMAG: Consultancy; Celgene: Consultancy; Apopharma: Consultancy; Biomed Informatics: Consultancy; Celgene: Consultancy; Ionis Pharmaceuticals: Consultancy; Vifor: Consultancy; Vifor: Consultancy; Ionis Pharmaceuticals: Consultancy; Biomed Informatics: Consultancy; World Care Clinical: Consultancy.

Modulation of Frontoparietal Neurovascular Dynamics in Working Memory.

Our perception of the world is represented in widespread, overlapping, and interactive neuronal networks of the cerebral cortex. A majority of physiological studies on the subject have focused on oscillatory synchrony as the binding mechanism for representation and transmission of neural information. Little is known, however, about the stability of that synchrony during prolonged cognitive operations that span more than just a few seconds. The present research, in primates, investigated the dynamic patterns of oscillatory synchrony by two complementary recording methods, surface field potentials (SFPs) and near-infrared spectroscopy (NIRS). The signals were first recorded during the resting state to examine intrinsic functional connectivity. The temporal modulation of coactivation was then examined on both signals during performance of working memory (WM) tasks with long delays (memory retention epochs). In both signals, the peristimulus period exhibited characteristic features in frontal and parietal regions. Examination of SFP signals over delays lasting tens of seconds, however, revealed alternations of synchronization and desynchronization. These alternations occurred within the same frequency bands observed in the peristimulus epoch, without a specific correspondence between any definite cognitive process (e.g., WM) and synchrony within a given frequency band. What emerged instead was a correlation between the degree of SFP signal fragmentation (in time, frequency, and brain space) and the complexity and efficiency of the task being performed. In other words, the incidence and extent of SFP transitions between synchronization and desynchronization-rather than the absolute degree of synchrony-augmented in correct task performance compared with incorrect performance or in a control task without WM demand. An opposite relationship was found in NIRS: increasing task complexity induced more uniform, rather than fragmented, NIRS coactivations. These findings indicate that the particular features of neural oscillations cannot be linearly mapped to cognitive functions. Rather, information and the cognitive operations performed on it are primarily reflected in their modulations over time. The increased complexity and fragmentation of electrical frequencies in WM may reflect the activation of hierarchically diverse cognits (cognitive networks) in that condition. Conversely, the homogeneity in coherence of NIRS responses may reflect the cumulative vascular reactions that accompany that neuroelectrical proliferation of frequencies and the longer time constant of the NIRS signal. These findings are directly relevant to the mechanisms mediating cognitive processes and to physiologically based interpretations of functional brain imaging.

Effects of Physical Exercise on Working Memory and Prefrontal Cortex Function in Post-Stroke Patients.

Physical exercise enhances prefrontal cortex activity and improves working memory performance in healthy older adults, but it is not clear whether this remains the case in post-stroke patients. Therefore, the aim of this study was to examine the acute effect of physical exercise on prefrontal cortex activity in post-stroke patients using near-infrared spectroscopy (NIRS). We studied 11 post-stroke patients. The patients performed Sternberg-type working memory tasks before and after moderate intensity aerobic exercise (40 % of maximal oxygen uptake) with a cycling ergometer for 15 min. We measured the NIRS response at the prefrontal cortex during the working memory task. We evaluated behavioral performance (response time and accuracy) of the working memory task. It was found that physical exercise improved behavioral performance of the working memory task compared with the control condition (p < 0.01). In addition, NIRS analysis indicated that physical exercise enhanced prefrontal cortex activation, particularly in the right prefrontal cortex (p < 0.05), during the working memory task compared with the control condition. These findings suggest that the moderate-intensity aerobic exercise enhances prefrontal cortex activity and improves working memory performance in post-stroke patients.

Possible Influences on the Interpretation of Functional Domain (FD) Near-Infrared Spectroscopy (NIRS): An Explorative Study.

The influence of subcutaneous adipose tissue (ATT) and oxygen (O2) delivery has been poorly defined in frequency domain (FD) near-infrared spectroscopy (NIRS). Therefore, the aim of this study was to investigate the possible influence of these variables on all FD NIRS responses using a reliable protocol. Moreover, these influences were also investigated when using relative oxy- and deoxyhemoglobin and -myoglobin (oxy[Hb + Mb] and deoxy[Hb + Mb]) values (in %). A regression analysis was carried out for ATT and maximal-minimum oxy[Hb + Mb], deoxy[Hb + Mb], oxygen saturation (SmO2), and total hemoglobin (totHb) amplitudes during an incremental cyclic contraction protocol (ICCP) in a group of 45 participants. Moreover, the same analysis was carried out between subcutaneous ATT and the relative oxy- and deoxy[Hb + Mb] values (in %). In the second part of this study, a regression analysis was performed for peak forearm blood flow (FBF) during ICCP and the absolute and relative NIRS values in a group of 37 participants. Significant exponential correlation coefficients were found between ATT and deoxy[Hb + Mb] (r = 0.53; P < 0.001), oxy[Hb + Mb] (r = 0.57; P < 0.001), and SmO2 amplitudes (r = 0.57; P < 0.001). No significant relations were found between ATT and relative oxy[Hb + Mb] (r = 0.37; P = 0.07) and deoxy[Hb + Mb] (r = 0.09; P = 0.82). Significant positive correlation coefficients were found between force at exhaustion and maximal FBF (r = 0.66; P < 0.001), maximal differences in deoxy[Hb + Mb] (r = 0.353; P = 0.032) and totHb (r = 0.512; P = 0.002) while no significant correlation coefficients were found between these maximal force values and maximal differences in oxy[Hb + Mb] (r = -0.267; P = 0.111) and SmO2 (r = -0.267; P = 0.111). Significant linear correlation coefficients were found between FBF and deoxy[Hb + Mb] (r = 0.51; P = 0.001), oxy[Hb + Mb] (r = -0.50; P = 0.001), SmO2 (r = -0.54; P = 0.001), and totHb amplitude (r = 0.61; P < 0.001). No significant correlations were found when using relative oxy[Hb + Mb] (r = -0.01; P = 0.957) and deoxy[Hb + Mb] (r = -0.02; P = 0.895). Based on these findings, caution is advised when using NIRS values, as subcutaneous ATT and O2 delivery significantly influence NIRS measurements. To eliminate these influences, use of relative deoxy[Hb + Mb] is advised, especially in clinical settings or in people with a higher subcutaneous ATT layer.

Development of Point of Care Testing Device for Neurovascular Coupling From Simultaneous Recording of EEG and NIRS During Anodal Transcranial Direct Current Stimulation.

This paper presents a point of care testing device for neurovascular coupling (NVC) from simultaneous recording of electroencephalogram (EEG) and near infrared spectroscopy (NIRS) during anodal transcranial direct current stimulation (tDCS). Here, anodal tDCS modulated cortical neural activity leading to hemodynamic response can be used to identify the impaired cerebral microvessels functionality. The impairments in the cerebral microvessels functionality may lead to impairments in the cerebrovascular reactivity (CVR), where severely reduced CVR predicts the chances of transient ischemic attack and ipsilateral stroke. The neural and hemodynamic responses to anodal tDCS were studied through joint imaging with EEG and NIRS, where NIRS provided optical measurement of changes in tissue oxy-(n}{}HbO2)n and deoxy-(n}{}Hbn) hemoglobin concentration and EEG captured alterations in the underlying neuronal current generators. Then, a cross-correlation method for the assessment of NVC underlying the site of anodal tDCS is presented. The feasibility studies on healthy subjects and stroke survivors showed detectable changes in the EEG and the NIRS responses to a 0.526 A/n}{}mathrm{m}^{2}n of anodal tDCS. The NIRS system was bench tested on 15 healthy subjects that showed a statistically significant (p < 0.01) difference in the signal-to-noise ratio (SNR) between the ON- and OFF-states of anodal tDCS where the mean SNR of the NIRS device was found to be 42.33 ± 1.33 dB in the ON-state and 40.67 ± 1.23 dB in the OFF-state. Moreover, the clinical study conducted on 14 stroke survivors revealed that the lesioned hemisphere with impaired circulation showed significantly (p < 0.01) less change in n}{}HbO2n than the nonlesioned side in response to anodal tDCS. The EEG study on healthy subjects showed a statistically significant (p < 0.05) decrease around individual alpha frequency in the alpha band (8−13 Hz) following anodal tDCS. Moreover, the joint EEG-NIRS imaging on 4 stroke survivors showed an immediate increase in the theta band (4−8 Hz) EEG activity after the start of anodal tDCS at the nonlesioned hemisphere. Furthermore, cross-correlation function revealed a significant (95% confidence interval) negative cross correlation only at the nonlesioned hemisphere during anodal tDCS, where the log-transformed mean-power of EEG within 0.5−11.25 Hz lagged n}{}HbO2n response in one of the stroke survivors with white matter lesions. Therefore, it was concluded that the anodal tDCS can perturb the local neural and the vascular activity (via NVC) which can be used for assessing regional NVC functionality where confirmatory clinical studies are required.

A noninvasive brain computer interface using visually-induced near-infrared spectroscopy responses

Visually-induced near-infrared spectroscopy (NIRS) response was utilized to design a brain computer interface (BCI) system. Four circular checkerboards driven by distinct flickering sequences were displayed on a LCD screen as visual stimuli to induce subjects’ NIRS responses. Each flickering sequence was a concatenated sequence of alternative flickering segments and resting segments. The flickering segment was designed with fixed duration of 3s whereas the resting segment was chosen randomly within 15–20s to create the mutual independencies among different flickering sequences. Six subjects were recruited in this study and subjects were requested to gaze at the four visual stimuli one-after-one in a random order. Since visual responses in human brain are time-locked to the onsets of visual stimuli and the flicker sequences of distinct visual stimuli were designed mutually independent, the NIRS responses induced by user's gazed targets can be discerned from non-gazed targets by applying a simple averaging process. The accuracies for the six subjects were higher than 90% after 10 or more epochs being averaged.

Pre-task prefrontal activation during cognitive processes in aging: a near-infrared spectroscopy study.

PurposeCognitive processing generally deteriorates as people age. Recent neuroimaging studies have shown that the prefrontal cortex (PFC) is involved in human-specific behavior, such as preparing for future actions and prospective memory; hence, the PFC may be voluntarily activated even during the “resting” condition that precedes task execution. The purpose of the present study was to investigate changes in voluntary pre-task activation as a result of aging using a paradigm that includes a longer intertrial interval (e.g., 30 sec) than has been used in previous studies.MethodsA total of 120 cognitively normal adults (young: 60, old: 60) participated in this near-infrared spectroscopy (NIRS) study. All subjects performed 6 repetitions of the working memory task, which included a 30 sec resting period and a 28.8 sec task period. The resting period was divided into baseline and pre-task (preT) periods, and the task period was divided into early easy task (eT) and late difficult task (dT) periods. We then normalized the data, analyzed the magnitude of task-related NIRS responses in each period and compared the results between groups using an analysis of variance test.ResultsStatistical analyses revealed a significant interaction between group × optode location × period, in which hemodynamic responses in the PFC during the preT period were smaller in the elderly in than young adults. By contrast, during the task period, the hemodynamic responses were higher in the lateral PFC in the elderly than in young adults. Spearman's rank correlation analysis showed a positive correlation between hemodynamic changes during the preT period in the PFC and correct answer ratios in both groups.ConclusionsThese findings suggest that more pre-task activation in the anterior PFC is related to better cognitive performance in humans. Thus, a reduction in this activation might partly explain cognitive decline in the elderly.