Cerebral Hemoglobin Research Articles

Investigating the Usability and Acute Effects of a Bedside Video Console to Prefrontal Cortical Activity Alterations: A Preclinical Study in Healthy Elderly.

Elderly people at risk of developing cognitive decline; e.g., following surgery, may benefit from structured, challenging, and repetitive cognitive video training. This study assessed usability and acute effects of a newly developed bedside console (COPHYCON). Fifteen healthy elderly individuals performed a one-time 80-min intervention, including cognitive video games aimed at improving awareness and selective attention. Perceived usefulness and perceived ease of use (Technology Acceptance Model) were assessed together with measures of the achieved game level, reaction times, (in-) correct responses during ALERT and SELECT game play. Further, prefrontal cortical involvement of the regional cerebral hemoglobin saturation (rS02%) assessed with functional near infrared spectroscopy (fNIRS) (n = 5) and EEG power (n = 10) was analyzed. All participants completed the study without any adverse events. Perceived usefulness and perceived ease of use (TAM scores range 1–7) of the system varied between 3.9 and 6.3. The game levels reached for awareness varied between 9 and 11 (initial score 8–10), for reaction speed between 439 and 469 ms, and for correct responses between 74.1 and 78.8%. The highest level for the selective attention games was 2 (initial score 1), where reaction speed varied between 439 and 469 ms, correct responses between 96.2 and 98.5%, respectively. The decrease of rS02% in the right prefrontal cortex during gameplay was significantly (p < 0.001) lower, compared to the left prefrontal cortex. Four participants yielded significant lower rS02% measures after exergaming with the ALERT games (p < 0.000), but not with the SELECT games. EEG recordings of theta power significantly decreased in the averaged ~0.25–0.75 time interval for the left prefrontal cortex sensor across the cognitive game levels between the ALERT 1 and SELECT 1, as well as between SELECT 1 and 2 games. Participants rated the usability of the COPHYCON training positively. Further results indicate that video gaming may be an effective measure to affect prefrontal cortical functioning in elderly. The results warrant a clinical explorative study investigating the feasibility of the COPHYCON in a clinical setting.

Shedding light on the neonatal brain: probing cerebral hemodynamics by diffuse optical spectroscopic methods

Investigating the cerebral physiology of healthy term newborns’ brains is important for better understanding perinatal brain injuries, of which the most common etiologies are hypoxia and ischemia. Hence, cerebral blood flow and cerebral oxygenation are important biomarkers of brain health. In this study, we employed a hybrid diffuse optical system consisting of diffuse correlation spectroscopy (DCS) and frequency-domain near infrared spectroscopy (FDNIRS) to measure hemoglobin concentration, oxygen saturation, and indices of cerebral blood flow and metabolism. We measured 30 term infants to assess the optical and physiological characteristics of the healthy neonatal brain in the frontal, temporal, and parietal lobes. We observed higher metabolism in the right hemisphere compared to the left and a positive correlation between gestational age and the level of cerebral hemoglobin concentration, blood volume, and oxygen saturation. Moreover, we observed higher cerebral blood flow and lower oxygen saturation in females compared to males. The delayed maturation in males and the sexual dimorphism in cerebral hemodynamics may explain why males are more vulnerable to perinatal brain injuries than females.

Psychophysiological Preference Monitoring by Cerebral Hemoglobin Measurement during Chewing an Apple Piece

In recent years, non-invasive monitoring of psychophysiological preferences for identifying unconscious reactions by measuring brain activity has attracted attention. However, no prior studies on the perception and consumption of food and drink have examined cerebral activity during chewing. Also, there is no research on food with multiple tastes that is eaten on a daily basis. Therefore, we investigated psychophysiological food-preference when chewing an apple by assessing cerebral blood flow (CBF) by using fNIRS (functional near-infrared spectroscopy). Gustatory sense and food preferences can be distinguished. However, instead of controlling for the taste, psychophysiological preference for information about taste was manipulated by presenting a nameplate showing the area where the food was produced. Independent component analysis (ICA) of CBF signals suggested that the average rate of taste identification with the nameplate was high (94.5%). We also tested the effects of chewing, which had not been investigated in previous studies. This was expected to expand the scope of research and its possibilities. It is suggested that methods of eliminating artefacts during chewing and methods of identifying preferences devised in this study would be useful for psychophysiological monitoring.

Contralateral cerebral hemoglobin oxygen saturation changes in patients undergoing thoracotomy with general anesthesia with or without paravertebral block: a randomized controlled trial.

Perioperative analgesia during thoracotomy is often achieved by combining paravertebral block (PVB) with general anesthesia (GA). Functional near-infrared spectroscopy (NIRS) can detect changes in cerebral oxygenation resulting from nociceptive stimuli in the awake state or under sedation. We used NIRS to measure changes in cerebral blood flow provoked by thoracotomy incision made under GA and determine how these changes were influenced by supplementation of GA with PVB. Thirty-four patients undergoing elective thoracotomy were enrolled. Patients were randomly assigned to a group receiving only GA, or GA combined with PVB (GA+PVB). Changes in cerebral oxygenated hemoglobin (ΔO2Hb), deoxygenated-Hb (ΔHHb), and total-Hb (ΔtotalHb) were evaluated by NIRS as surgery began. In the GA group, ΔO2Hb was significantly higher in the hemisphere contralateral to the side of surgery when the incision was made and 2min after incision compared with the ipsilateral side (start of surgery, P<0.01; 2min, P<0.05). In contrast, there were no significant changes in the ΔO2Hb at any of the time points in the GA+PVB group. Comparable with ΔO2Hb, the concentration of ΔtotalHb was significantly higher in the contralateral hemisphere in the GA group at the start of surgery (P<0.05). Changes in the cerebral O2Hb concentration were detected by NIRS immediately after surgical incision under GA, but not in the presence of a PNB. NIRS could be used to monitor surgical pain. PVB inhibited changes in oxygenation induced by incision-provoked pain.

Effectiveness Evaluation of Real-Time Scalp Signal Separating Algorithm on Near-Infrared Spectroscopy Neurofeedback.

Near-infrared spectroscopy (NIRS), one of the candidates to be used in a neurofeedback system or brain-computer interface (BCI), measures the brain activity by monitoring the changes in cerebral hemoglobin concentration. However, hemodynamic changes in the scalp may affect the NIRS signals. In order to remove the superficial signals when NIRS is used in a neurofeedback system or BCI, real-time processing is necessary. Real-time scalp signal separating (RT-SSS) algorithm, which is capable of separating the scalp-blood signals from NIRS signals obtained in real-time, may thus be applied. To demonstrate its effectiveness, two separate neurofeedback experiments were conducted. In the first experiment, the feedback signal was the raw NIRS signal recorded while in the second experiment, deep signal extracted using RT-SSS algorithm was used as the feedback signal. In both experiments, participants were instructed to control the feedback signal to follow a predefined track. Accuracy scores were calculated based on the differences between the trace controlled by feedback signal and the targeted track. Overall, the second experiment yielded better performance in terms of accuracy scores. These findings proved that RT-SSS algorithm is beneficial for neurofeedback.

Correlation between Cerebral Hemodynamic and Perfusion Pressure Changes in Non-Human Primates.

The mechanism that maintains a stable blood flow in the brain despite changes in cerebral perfusion pressure (CPP), and therefore guaranties a constant supply of oxygen and nutrients to the neurons, is known as cerebral autoregulation (CA). In a certain range of CPP, blood flow is mediated by a vasomotor adjustment in vascular resistance through dilation of blood vessels. CA is known to be impaired in diseases like traumatic brain injury, Parkinson's disease, stroke, hydrocephalus and others. If CA is impaired, blood flow and pressure changes are coupled and the oxygen supply might be unstable. Lassen's blood flow autoregulation curve describes this mechanism, where a plateau of stable blood flow in a specific range of CPP corresponds to intact autoregulation. Knowing the limits of this plateau and maintaining CPP within these limits can improve patient outcome. Since CPP is influenced by both intracranial pressure and arterial blood pressure, long term changes in either can lead to autoregulation impairment. Non-invasive methods for monitoring blood flow autoregulation are therefore needed. We propose to use Near infrared spectroscopy (NIRS) to fill this need. NIRS is an optical technique, which measures microvascular changes in cerebral hemoglobin concentration. We pe erformed experiments on non-human primates during exsanguination to demonstrate that the limits of blood flow autoregulation can be accessed with NIRS.

Abstract TP400: Evoked Functional Cerebral Hemodynamic and Metabolic Responses in Premature Infants with and without Germinal Matrix Hemorrhage

We have created an innovative new method which uses frequency domain near-infrared spectroscopy (FDNIRS) in combination with diffuse correlation spectroscopy (DCS) to quantitatively measure cerebral blood flow (CBF) and oxygen metabolism (CMRO 2 ) right at the infant’s bedside. We have previously found CBF and CMRO 2 are more sensitive indicators of cerebral pathophysiology than hemoglobin saturation (SO 2 ). Using FDNIRS-DCS, we had found extremely premature infants with germinal matrix hemorrhage (GMH) have lower cerebral blood flow (CBF) and oxygen metabolism (CMRO 2 ) than gestational age-matched controls. For this study, we investigate whether GMH, along with age and hematocrit levels, affect evoked hemodynamic responses. The study protocol was reviewed and approved by the Institutional Review Board for Partners Healthcare. We enrolled eleven premature infants in the neonatal intensive care unit at Brigham and Women’s Hospital. Three of them had Grade I GMH diagnosed by head ultrasound on the first three days of life. We integrated continuous wave NIRS (CWNIRS) with DCS to measure dynamic changes of cerebral hemoglobin concentrations (HbO) and CBF in response to somatosensory stimuli. For each measurement, we measured differential path length factors and baseline cerebral hemoglobin concentrations with FDNIRS to quantify relative hemodynamic and metabolic changes (rHbO, rCBF and rCMRO 2 ) in response to tactile stimulation. We observed a faster response time to reach peak value in preterm infants with increasing postmenstrual age (PMA), demonstrating the response matures with age to become more adult-like (r=-0.513, p=0.007). In addition, infants measured at older PMA tend to have responses with a larger undershoot in HbO. However, the HbO undershoot did not translate into an undershoot in CMRO 2 . The HbO undershoot may therefore be a consequence of low hematocrit during the first two months of life which results in insufficient oxygen supply and leads to abnormally large oxygen extraction from the blood. We found the activation pattern of Grade I GMH infants did not differ from premature infants without hemorrhage. The study is ongoing and shows our method is suitable to measure cerebral maturation in neonates with hemorrhage.

Classification of Desired Motion Force Based On Cerebral Hemoglobin Information*

Strength training using patients’ desired force level is helpful to improve training effect and promote rehabilitation. Generally, force levels are recognized by applying EMG or biomechanical information, these methods were not suitable for patients who lost important muscle groups or have weakened muscle functions. This paper proposed a method for identifying force level based on cerebral hemoglobin information, rather than the information depending on limbs. Ten subjects performed pedaling movement in three force levels. Features were extracted in both the time-domain and frequency-domain, with deoxygenated hemoglobin (deoxy) and the difference between oxygenated hemoglobin (oxy) and deoxy as parameters. Important frequency bands (0.01-0.03Hz, 0.03-0.06Hz, 0.06-0.09Hz, 0.09-0.12Hz) were confirmed by performing power spectrum density analysis. And significant measure channels were selected by performing one-way analyses of variance on three time periods around the start of movement. Force level was recognized by applying extreme learning machine (ELM). The corresponding precision rate was up to 78.7%. The proposed identification method was not restricted to the existence of limbs or the strength of limb information. It was realized based on brain information recorded in a real movement environment; it is helpful to realize the desired force level of subjects and to provide a control command for rehabilitation training equipment.

To Classify Spontaneous Motion Intention of Step Size by Using Cerebral Hemoglobin Information

To improve the effect of walking-assistive devices, there is a need for it to develop devices controlled by spontaneous intention of patients. In recent study, we identified spontaneous motion intention of walking step based on cerebral hemoglobin information. Twenty healthy subjects performed walking tasks in three levels of step size (small, normal and large). According to distribution features of signals’ power spectral-density, six frequency bands (0-0.18Hz with an interval of 0.03Hz for each band width) divided by applying wavelet packets decomposition were mainly analyzed. Feature vectors were extracted from the difference between oxygenated hemoglobin (oxyHb) and deoxygenated hemoglobin (dexoyHb) in different measuring channels in the six frequency bands. Support vector machine (SVM) method was utilized to classify the three levels of step sizes. Mean recognition accuracy achieved up to 83.3%. The result indicated that it is possible to identify spontaneous walking by using cerebral hemoglobin information. This is helpful for enhancing the intelligence of walking-assistive devices and motivating the active control of patients, which further is profitable for enhancing self-confidence of patients.

Hypoxic-Ischemic Encephalopathy-Associated Liver Fatty Degeneration and the Effects of Therapeutic Hypothermia in Newborn Piglets

Background: Although liver can be injured under the hypoxic-ischemic encephalopathy (HIE) condition, there is currently no histopathological evidence. Therapeutic hypothermia is used to protect the brain; however, the therapeutic potential for concomitant liver injury is unknown. Objectives: This study aimed to histopathologically prove HIE-associated liver injury and to investigate the influence of therapeutic hypothermia in a newborn piglet HIE model. Methods: Eighteen newborn piglets were divided into 3 groups: control (n = 4), HIE (n = 8), and therapeutic hypothermia (n = 6) groups. The hypoxic insult was induced by decreasing the fraction of inspiratory oxygen from 21 to 2-4% over 40 min while monitoring cerebral blood volume and cerebral hemoglobin oxygen saturation. For therapeutic hypothermia, whole-body cooling at 33-34°C was administered for 24 h after the hypoxic insult. We hematologically and histopathologically investigated the liver injury in all groups. Results: Alanine transaminase and lactate dehydrogenase levels in the HIE group were significantly elevated compared with those in the control group. Micro-lipid droplet accumulation in the periportal zone, but not in the perivenous zone, was significantly greater in the HIE group than in the control group and significantly smaller in the therapeutic hypothermia group than in the HIE group. Conclusions: We demonstrated that micro-lipid droplet accumulation in the cytoplasm of hepatocytes in the periportal zone occurs under the HIE condition and that this accumulation is suppressed by therapeutic hypothermia.

Quantification of extra-cerebral and cerebral hemoglobin concentrations during physical exercise using time-domain near infrared spectroscopy.

Fitness is known to have beneficial effects on brain anatomy and function. However, the understanding of mechanisms underlying immediate and long-term neurophysiological changes due to exercise is currently incomplete due to the lack of tools to investigate brain function during physical activity. In this study, we used time-domain near infrared spectroscopy (TD-NIRS) to quantify and discriminate extra-cerebral and cerebral hemoglobin concentrations and oxygen saturation (SO2) in young adults at rest and during incremental intensity exercise. In extra-cerebral tissue, an increase in deoxy-hemoglobin (HbR) and a decrease in SO2 were observed while only cerebral HbR increased at high intensity exercise. Results in extra-cerebral tissue are consistent with thermoregulatory mechanisms to dissipate excess heat through skin blood flow, while cerebral changes are in agreement with cerebral blood flow (CBF) redistribution mechanisms to meet oxygen demand in activated regions during exercise. No significant difference was observed in oxy- (HbO2) and total hemoglobin (HbT). In addition HbO2, HbR and HbT increased with subject's peak power output (equivalent to the maximum oxygen volume consumption; VO2 peak) supporting previous observations of increased total mass of red blood cells in trained individuals. Our results also revealed known gender differences with higher hemoglobin in men. Our approach in quantifying both extra-cerebral and cerebral absolute hemoglobin during exercise may help to better interpret past and future continuous-wave NIRS studies that are prone to extra-cerebral contamination and allow a better understanding of acute cerebral changes due to physical exercise.

Computational Pipeline for NIRS-EEG Joint Imaging of tDCS-Evoked Cerebral Responses—An Application in Ischemic Stroke

Transcranial direct current stimulation (tDCS) modulates cortical neural activity and hemodynamics. Electrophysiological methods (electroencephalography-EEG) measure neural activity while optical methods (near-infrared spectroscopy-NIRS) measure hemodynamics coupled through neurovascular coupling (NVC). Assessment of NVC requires development of NIRS-EEG joint-imaging sensor montages that are sensitive to the tDCS affected brain areas. In this methods paper, we present a software pipeline incorporating freely available software tools that can be used to target vascular territories with tDCS and develop a NIRS-EEG probe for joint imaging of tDCS-evoked responses. We apply this software pipeline to target primarily the outer convexity of the brain territory (superficial divisions) of the middle cerebral artery (MCA). We then present a computational method based on Empirical Mode Decomposition of NIRS and EEG time series into a set of intrinsic mode functions (IMFs), and then perform a cross-correlation analysis on those IMFs from NIRS and EEG signals to model NVC at the lesional and contralesional hemispheres of an ischemic stroke patient. For the contralesional hemisphere, a strong positive correlation between IMFs of regional cerebral hemoglobin oxygen saturation and the log-transformed mean-power time-series of IMFs for EEG with a lag of about −15 s was found after a cumulative 550 s stimulation of anodal tDCS. It is postulated that system identification, for example using a continuous-time autoregressive model, of this coupling relation under tDCS perturbation may provide spatiotemporal discriminatory features for the identification of ischemia. Furthermore, portable NIRS-EEG joint imaging can be incorporated into brain computer interfaces to monitor tDCS-facilitated neurointervention as well as cortical reorganization.

FNIR Study of Cognitive Decline and Reading in Parkinson’s Disease: Preliminary Data

As yet, there has been little research applying functional near-infrared spectroscopy (fNIR) neuroimaging studies to aspects of brain activation such as cognitive decline or working memory deficits with reading difficulties in Parkinson’s disease (PD). The purpose of this study is to investigate cerebral hemoglobin concentration changes related to reading and cognitive load tasks in an individual with PD. An individual with PD and a healthy normal person of the same age with no history of neurogenic disorders participated in this study. Functional near-infrared spectroscopy (fNIR) measurements were recorded while the participants carried out a reading task (grandfather passage) and four cognitive load tasks. The fNIR results for the reading task revealed significant differences in the changes in the oxygen concentration levels experienced by the two participants and this was also manifested in both the left and right hemispheres. There were also significant differences between the two participants across all of the cognitive tasks. Unlike the non-PD participant, the PD participant did not exhibit any significant differences among the four cognitive tasks and no significant oxygenation change between the left and right hemispheres when performing cognitive tasks 1 and 4 was observed. These results suggest that PD patients either lack sufficient brain activation to complete linguistic or cognitive tasks or are unable to use oxygenation effectively in a specific brain area when seeking to accomplish these types of tasks.

Tutorial on platform for optical topography analysis tools.

Optical topography/functional near-infrared spectroscopy (OT/fNIRS) is a functional imaging technique that noninvasively measures cerebral hemoglobin concentration changes caused by neural activities. The fNIRS method has been extensively implemented to understand the brain activity in many applications, such as neurodisorder diagnosis and treatment, cognitive psychology, and psychiatric status evaluation. To assist users in analyzing fNIRS data with various application purposes, we developed a software called platform for optical topography analysis tools (POTATo). We explain how to handle and analyze fNIRS data in the POTATo package and systematically describe domain preparation, temporal preprocessing, functional signal extraction, statistical analysis, and data/result visualization for a practical example of working memory tasks. This example is expected to give clear insight in analyzing data using POTATo. The results specifically show the activated dorsolateral prefrontal cortex is consistent with previous studies. This emphasizes analysis robustness, which is required for validating decent preprocessing and functional signal interpretation. POTATo also provides a self-developed plug-in feature allowing users to create their own functions and incorporate them with established POTATo functions. With this feature, we continuously encourage users to improve fNIRS analysis methods. We also address the complications and resolving opportunities in signal analysis.

Hemodynamic signals in fNIRS.

Near-infrared spectroscopy (NIRS) was originally designed for clinical monitoring of tissue oxygenation, and it has also been developed into a useful tool in neuroimaging studies, with the so-called functional NIRS (fNIRS). With NIRS, cerebral activation is detected by measuring the cerebral hemoglobin (Hb), where however, the precise correlation between NIRS signal and neural activity remains to be fully understood. This can in part be attributed to the situation that NIRS signals are inherently subject to contamination by signals arising from extracerebral tissue. In recent years, several approaches have been investigated to distinguish between NIRS signals originating in cerebral tissue and signals originating in extracerebral tissue. Selective measurements of cerebral Hb will enable a further evolution of fNIRS. This chapter is divided into six sections: first a summary of the basic theory of NIRS, NIRS signals arising in the activated areas, correlations between NIRS signals and fMRI signals, correlations between NIRS signals and neural activities, and the influence of a variety of extracerebral tissue on NIRS signals and approaches to this issue are reviewed. Finally, future prospects of fNIRS are described.

Perioperative cerebral hemodynamics and oxygen metabolism in neonates with single-ventricle physiology.

Congenital heart disease (CHD) patients are at risk for neurodevelopmental delay. The etiology of these delays is unclear, but abnormal prenatal cerebral maturation and postoperative hemodynamic instability likely play a role. A better understanding of these factors is needed to improve neurodevelopmental outcome. In this study, we used bedside frequency-domain near infrared spectroscopy (FDNIRS) and diffuse correlation spectroscopy (DCS) to assess cerebral hemodynamics and oxygen metabolism in neonates with single-ventricle (SV) CHD undergoing surgery and compared them to controls. Our goals were 1) to compare cerebral hemodynamics between unanesthetized SV and healthy neonates, and 2) to determine if FDNIRS-DCS could detect alterations in cerebral hemodynamics beyond cerebral hemoglobin oxygen saturation (SO 2). Eleven SV neonates were recruited and compared to 13 controls. Preoperatively, SV patients showed decreased cerebral blood flow (CBFi ), cerebral oxygen metabolism (CMRO 2i ) and SO 2; and increased oxygen extraction fraction (OEF) compared to controls. Compared to preoperative values, unstable postoperative SV patients had decreased CMRO 2i and CBFi , which returned to baseline when stable. However, SO 2 showed no difference between unstable and stable states. Preoperative SV neonates are flow-limited and show signs of impaired cerebral development compared to controls. FDNIRS-DCS shows potential to improve assessment of cerebral development and postoperative hemodynamics compared to SO 2 alone.

Corticospinal excitability changes to anodal tDCS elucidated with NIRS-EEG joint-imaging: An ischemic stroke study.

Transcranial direct current stimulation (tDCS) has been shown to modulate corticospinal excitability. We used near-infrared spectroscopy (NIRS)-electroencephalography (EEG) joint-imaging during and after anodal tDCS to measure changes in mean cerebral haemoglobin oxygen saturation (rSO2) along with changes in the log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz. In two separate studies, we investigated local post-tDCS alterations from baseline at the site of anodal tDCS using NIRS-EEG/tDCS joint-imaging as well as local post-tDCS alterations in motor evoked potentials (MEP)-measure of corticospinal excitability. In the first study, we found that post-tDCS changes in the mean rSO2 from baseline mostly correlated with the corresponding post-tDCS change in log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz. Moreover, a decrease in log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz corresponded with an increase in the MEP-measure of corticospinal excitability--found in the second study. Therefore, we propose to combine NIRS-EEG/tDCS joint-imaging with corticospinal excitability investigation in a single study to confirm these finding. Furthermore, we postulate that the innovative technologies for portable NIRS-EEG neuroimaging may be leveraged to objectively quantify the progress (e.g., corticospinal excitability alterations) and dose tDCS intervention as an adjuvant treatment during neurorehabilitation.

Anterior temporal artery tap to identify systemic interference using short-separation NIRS measurements: A NIRS/EEG-tDCS study.

Transcranial direct current stimulation (tDCS) has been shown to modulate neural activity. Neural activity has been shown to be closely related, spatially and temporally, to cerebral blood flow (CBF) that supplies glucose via neurovascular coupling. Therefore, noninvasive and continuous monitoring of neural activity is possible with a measure of cerebral hemoglobin oxygenation using near-infrared spectroscopy (NIRS). In principal accordance, NIRS can capture the hemodynamic response to tDCS but the challenge remains in removing the systemic interference occurring in the superficial layers of the head that are also affected by tDCS. An approach may be to use short optode separations to measure systemic hemodynamic fluctuations occurring in the superficial layers which can then be used as regressors to remove the systemic contamination. Here, we demonstrate that temporal artery tap may be used to better identify systemic interference using this short-separation NIRS. Moreover, NIRS-EEG joint-imaging during anodal tDCS was used to measure changes in mean cerebral haemoglobin oxygen saturation (rSO2) along with changes in the log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz. We found that percent change in the mean rSO2 better correlated with the corresponding percent change in log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz frequency band after removing the systemic contamination using the temporal artery tap method. Based on our findings, we propose that anterior temporal artery tap technique presented in this paper may be able to classify carotid stenosis, external carotid artery stenosis, and internal carotid artery stenosis patients using the laterality in the hemodynamic response evoked by anodal tDCS both at the brain as well as at the superficial layers. These findings may have important implications for both prognosis and rehabilitation of patients with intracranial stenosis.

The Effect of Decreasing Flow Rate on Cerebral Hemodynamics During Veno-Arterial Extracorporeal Membrane Oxygenation in Piglets.

To explore the influence of decreasing flow rate on cerebral hemodynamics during veno-arterial extracorporeal membrane oxygenation (va-ECMO), six normoxemic and six hypoxemic piglets were put on va-ECMO. The ECMO flow rate was decreased from the maximal achievable level to 50 mL min1 with steps of 50 mL min1 every 2 minutes. Changes in mean arterial blood pressure (MABP), left common carotid artery blood flow (Qcar), and other physiologic variables were continuously measured. Changes in concentrations of oxyhemoglobin and deoxyhemoglobin were measured using near infrared spectrophotometry (NIRS). Changes in difference between cerebral oxygen hemoglobin and deoxyhemoglobin concentration (ΔcHbD) and total hemoglobin concentration (ΔctHb) were calculated. ΔcHbD represents changes in cerebral blood flow (CBF), and ΔctHb reflects changes in cerebral blood volume (CBV). Data analysis was performed using mixed models and demonstrated a significant positive correlation between ECMO flow and, respectively, MABP (r = 0.7, p < 0.001), Qcar (r = 0.7, p < 0.001), cHbD (r = 0.8, p < 0.001), and ctHb (r = 0.7, p < 0.001). There was no significant relation between oxygenation state preceding ECMO and Qcar, cHbD, and ctHb during decreasing ECMO flow rate. We conclude that decreasing ECMO flow rate ultimately leads to concurrent decrease in MABP, CBF, and CBV.

Idarucizumab Improves Outcome in Murine Brain Hemorrhage Related to Dabigatran.

Lack of specific antidotes is a major concern in intracerebral hemorrhage (ICH) related to direct anticoagulants including dabigatran (OAC-ICH). We examined the efficacy of idarucizumab, an antibody fragment binding to dabigatran, in a mouse model of OAC-ICH. Dabigatran etexilate (DE) dose-dependently prolonged diluted thrombin time and tail-vein bleeding time, which were reversed by idarucizumab. Pretreatment with DE increased intracerebral hematoma volume and cerebral hemoglobin content. Idarucizumab in equimolar dose prevented excess hematoma expansion for both DE doses. In more extensive ICH, idarucizumab significantly reduced mortality. Thus, idarucizumab prevents excess intracerebral hematoma formation in mice anticoagulated with dabigatran and reduces mortality.