Decrease In oxy-Hb Research Articles

Erythroid anion Exchanger-1 (band 3) transports nitrite for nitric oxide metabolism

Nitrite (NO2−) interacts with hemoglobin (Hb) in various ways to regulate blood flow. During hypoxic vasodilation, nitrite is reduced by deoxyHb to yield nitric oxide (NO). While NO, a hydrophobic gas, could freely diffuse across the cell membrane, how the reactant nitrite anion could permeate through the red blood cell (RBC) membrane remains unclear. We hypothesized that Cl−/HCO3− anion exchanger-1 (AE1; band 3) abundantly embedded in the RBC membrane could transport NO2−, as HCO3− and NO2− exhibit similar hydrated radii. Here, we monitored NO/N2O3 generated from NO2− inside human RBCs by DAF-FM fluorophore. NO2−, not NO3−, increased intraerythrocytic DAF-FM fluorescence. To test the involvement of AE1-mediated transport in intraerythrocytic NO/N2O3 production from nitrite, we lowered Cl− or HCO3− in the RBC-incubating buffer by 20 % and indeed observed slower rise of the DAF-FM fluorescence. Anti-extracellular AE1, but not anti-intracellular AE1 antibodies, reduced the rates of NO formation from nitrite. The AE1 blocker DIDS similarly reduced the rates of NO/N2O3 production from nitrite in a dose-dependent fashion, confirming that nitrite entered RBCs through AE1. Nitrite inside the RBCs reacted with both deoxyHb and oxyHb, as evidenced by 6.1 % decrease in deoxyHb, 14.7 % decrease in oxyHb, and 20.7 % increase in methemoglobin (metHb). Lowering Cl− in the milieu equally delayed metHb production from nitrite-oxyHb and nitrite-deoxyHb reactions. Thus, AE1-mediated NO2− transport facilitates NO2−-Hb reactions inside the red cells, supporting NOx metabolism in circulation.

Frequent, Short Physical Activity Breaks Reduce Prefrontal Cortex Activation but Preserve Working Memory in Middle-Aged Adults: ABBaH Study.

Prolonged sitting is increasingly common and may possibly be unfavorable for cognitive function and mood. In this randomized crossover study, the effects of frequent, short physical activity breaks during prolonged sitting on cognitive task-related activation of the prefrontal cortex were investigated. The effects on working memory, psychological factors, and blood glucose were also examined, and whether arterial stiffness moderated prefrontal cortex activation. Thirteen subjects (mean age 50.5 years; eight men) underwent three 3-h sitting conditions, interrupted every 30-min by a different 3-min break on separate, randomized-ordered days: seated social interactions (SOCIAL), walking (WALK), or simple resistance activities (SRA). Arterial stiffness was assessed at baseline. Before and after each 3-h condition, psychological factors (stress, mood, sleepiness, and alertness) were assessed through questionnaires and functional near-infrared spectroscopy (fNIRS) was used to measure changes in prefrontal oxygenated hemoglobin (Oxy-Hb), indicative of cortical activation, while performing working memory tasks [1- (baseline), 2-, and 3-back]. Blood glucose levels were continuously measured throughout the conditions. Results revealed no significant changes in Oxy-Hb during the 2-back compared with the 1-back test in any condition, and no time-by-condition interactions. During the 3-back test, there was a significant decrease in Oxy-Hb compared with the 1-back after the WALK condition in the right prefrontal cortex, but there were no time-by-condition interactions, although 3-back reaction time improved only in the WALK condition. Mood and alertness improved after the WALK condition, which was significantly different from the SOCIAL condition. Arterial stiffness moderated the effects, such that changes in Oxy-Hb were significantly different between WALK and SOCIAL conditions only among those with low arterial stiffness. Blood glucose during the interventions did not differ between conditions. Thus, breaking up prolonged sitting with frequent, short physical activity breaks may reduce right prefrontal cortex activation, with improvements in some aspects of working memory, mood, and alertness.Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT04137211.

Effect of Adrenaline on Cerebral Blood Oxygenation Measured byNIRS in a Rat Asphyxia Cardiac Arrest Model.

Adrenaline is an important pharmacologic treatment during cardiac arrest (CA) for resuscitation. Recent studies suggest that adrenaline increases the likelihood of return of spontaneous circulation (ROSC) but does not contribute to improving neurological outcomes of CA. The mechanisms have not been elucidated yet. A bimodal increase in mean arterial pressure (MAP) is observed after adrenaline injection in rodent CA models (Okuma et al. Intensive Care Med Exp 7(1), 2019). In this study, we focused on alteration of systemic arterial pressure in conjunction with the measurement of cerebral blood oxygenation (CBO) such as oxyhemoglobin (Oxy-Hb), deoxyhemoglobin (Deoxy-Hb), and tissue oxygenation index (TOI) by near-infrared spectroscopy (NIRS). Male Sprague-Dawley rats were used. We attached NIRS between the nasion and the upper cervical spine. Rats underwent 10minute asphyxia to induce CA. Then, cardiopulmonary resuscitation (CPR) was started, followed by a 20μg/kg of bolus adrenaline injection at 30seconds of CPR. This injection accelerated the first increase in MAP, and ROSC was observed with an abrupt increase in CBO. Interestingly, the second increase in MAP, once it exceeded a certain value, was accompanied by paradoxical decreases of Oxy-Hb and TOI while Deoxy-Hb increased. Based on this finding, we compared Oxy-Hb, Deoxy-Hb, and TOI at the first MAP ≈ 100mmHg and the second MAP ≈ 100mmHg. The average of Oxy-Hb and TOI from the 13 animals significantly decreased at the second increase in MAP over 100mmHg while Deoxy-Hb significantly increased. NIRS identified a decrease in Oxy-Hb after ROSC. These findings may be a clue in understanding the mechanism of how and why adrenaline alters the neurological outcomes of CA post resuscitation.

Effect of Adrenaline on Cerebral Blood Oxygenation Measured byNIRS in a Rat Asphyxia Cardiac Arrest Model.

Adrenaline is an important pharmacologic treatment during cardiac arrest (CA) for resuscitation. Recent studies suggest that adrenaline increases the likelihood of return of spontaneous circulation (ROSC) but does not contribute to improving neurological outcomes of CA. The mechanisms have not been elucidated yet. A bimodal increase in mean arterial pressure (MAP) is observed after adrenaline injection in rodent CA models [17]. In this study, we focused on alteration of systemic arterial pressure in conjunction with the measurement of cerebral blood oxygenation (CBO) such as oxyhemoglobin (Oxy-Hb), deoxyhemoglobin (Deoxy-Hb), and tissue oxygenation index (TOI) by near-infrared spectroscopy (NIRS). Male Sprague-Dawley rats were used. We attached NIRS between the nasion and the upper cervical spine. Rats underwent 10-minute asphyxia to induce CA. Then, cardiopulmonary resuscitation (CPR) was started, followed by a 20μg/kg of bolus adrenaline injection at 30seconds of CPR. This injection accelerated the first increase in MAP, and ROSC was observed with an abrupt increase in CBO. Interestingly, the second increase in MAP, once it exceeded a certain value, was accompanied by paradoxical decreases of Oxy-Hb and TOI, while Deoxy-Hb increased. Based on this finding, we compared Oxy-Hb, Deoxy-Hb, and TOI at the first MAP ≈ 100mmHg and the second MAP ≈ 100mmHg. The average of Oxy-Hb and TOI from the 13 animals significantly decreased at the second increase in MAP over 100mmHg, while Deoxy-Hb significantly increased. NIRS identified a decrease in Oxy-Hb after ROSC. These findings may be a clue to understanding the mechanism of how and why adrenaline alters the neurological outcomes of CA post-resuscitation.

Retraction Note to: Effect of Adrenaline on Cerebral Blood Oxygenation Measured by NIRS in a Rat Asphyxia Cardiac Arrest Model.

Adrenaline is an important pharmacologic treatment during cardiac arrest (CA) for resuscitation. Recent studies suggest that adrenaline increases the likelihood of return of spontaneous circulation (ROSC) but does not contribute to improving neurological outcomes of CA. The mechanisms have not been elucidated yet. A bimodal increase in mean arterial pressure (MAP) is observed after adrenaline injection in rodent CA models (Okuma et al. Intensive Care Med Exp 7(1), 2019). In this study, we focused on alteration of systemic arterial pressure in conjunction with the measurement of cerebral blood oxygenation (CBO) such as oxyhemoglobin (Oxy-Hb), deoxyhemoglobin (Deoxy-Hb), and tissue oxygenation index (TOI) by near-infrared spectroscopy (NIRS). Male Sprague-Dawley rats were used. We attached NIRS between the nasion and the upper cervical spine. Rats underwent 10 minute asphyxia to induce CA. Then, cardiopulmonary resuscitation (CPR) was started, followed by a 20 μg/kg of bolus adrenaline injection at 30 seconds of CPR. This injection accelerated the first increase in MAP, and ROSC was observed with an abrupt increase in CBO. Interestingly, the second increase in MAP, once it exceeded a certain value, was accompanied by paradoxical decreases of Oxy-Hb and TOI while Deoxy-Hb increased. Based on this finding, we compared Oxy-Hb, Deoxy-Hb, and TOI at the first MAP ≈ 100 mmHg and the second MAP ≈ 100 mmHg. The average of Oxy-Hb and TOI from the 13 animals significantly decreased at the second increase in MAP over 100 mmHg while Deoxy-Hb significantly increased. NIRS identified a decrease in Oxy-Hb after ROSC. These findings may be a clue in understanding the mechanism of how and why adrenaline alters the neurological outcomes of CA post resuscitation.

Deactivation of the prefrontal cortex during exposure to pleasantly-charged emotional challenge

Our laboratory reported that facial skin blood flow may serve as a sensitive tool to assess an emotional status and that both prefrontal oxygenation (as index of regional cerebral blood flow) and facial skin blood flow decrease during positively-charged emotional stimulation, without changing hand skin blood flow and arterial pressure. However, the focal location of the prefrontal responses in concentration of oxygenated haemoglobin (Oxy-Hb) that correlate with peripheral autonomic reaction remained unknown. This study was undertaken using 22-channel near-infrared spectroscopy to reveal spatial distribution of the responses in Oxy-Hb within the prefrontal cortex (PFC) during emotionally-charged audiovisual stimulation. Pleasantly-charged (comedy) stimulation caused a substantial decrease of Oxy-Hb in all regions of the PFC in 18 subjects, especially in the rostroventral frontopolar PFC, whereas negatively-charged (horror) or neutral stimulation (landscape) exhibited a weaker decrease or insignificant change in the prefrontal Oxy-Hb. In the rostral parts of the dorsolateral and ventral frontopolar PFC, the oxygenation response during comedy stimulation exhibited the most significant positive correlation with the decrease in facial skin blood flow. Thus the rostral regions of the PFC play a role in recognition and regulation of positive emotion and may be linked with neurally-mediated vasoconstriction of facial skin blood vessels.

Decreased prefrontal oxygenation elicited by stimulation of limb mechanosensitive afferents during cycling exercise.

Our laboratory reported using near-infrared spectroscopy that feedback from limb mechanoafferents may decrease prefrontal oxygenated-hemoglobin concentration (Oxy-Hb) during the late period of voluntary and passive cycling. To test the hypothesis that the decreased Oxy-Hb of the prefrontal cortex would be augmented depending on the extent of limb mechanoafferent input, the prefrontal Oxy-Hb response was measured during motor-driven one- and two-legged passive cycling for 1 min at various revolutions of pedal movement in 19 subjects. Furthermore, we examined whether calculated tissue oxygenation index (TOI) decreased during passive cycling as the Oxy-Hb did, simultaneously assessing blood flows of extracranial cutaneous tissue and the common and internal carotid arteries (CCA and ICA) with laser and ultrasound Doppler flowmetry. Minute ventilation and cardiac output increased and peripheral resistance decreased during passive cycling, depending on both revolutions of pedal movement and number of limbs, whereas mean arterial blood pressure did not change. Passive cycling did not change end-tidal CO2, suggesting absence of a hypocapnic change. Prefrontal Oxy-Hb decreased during passive cycling, being in proportion to revolution of pedal movement but not number of cycling limbs. In addition, prefrontal TOI decreased during passive cycling as Oxy-Hb did, whereas blood flows of forehead cutaneous tissue, CCA, and ICA did not change significantly. Thus, a decrease in Oxy-Hb reflected a decrease in tissue blood flow of the intracerebral vasculature but not the extracerebral compartment. It is likely that feedback from mechanoafferents decreased regional cerebral blood flow of the prefrontal cortex in relation to the revolutions of pedal movement.

A Functional Near-Infrared Spectroscopy Study of High-Frequency Yoga Breathing Compared to Breath Awareness.

BackgroundHigh-frequency yoga breathing (breath rate of 2.0 Hz) has been associated with changes in oxy-hemoglobin in the prefrontal region of the brain. The present study assessed the effects of high-frequency yoga breathing (HFYB) at 1.0 Hz on frontal oxy-hemoglobin (oxy-Hb) and deoxy-hemoglobin (deoxy-Hb).Material/MethodsForty healthy male participants were recruited for the study. The experimental group consisted of 20 participants 23–40 years old (group mean ±S.D., 26.4±4.7 years) with at least 3 months of experience performing HFYB (group mean ±S.D., 16.3±9.8 months). The control group consisted of 20 participants ages 23–38 years (group mean age ± S.D., 27.4±4.1 years), who were seated quietly for the same duration and their average experience of yoga practice was (±S.D.) 4.3±2.7 months. Each participant in the experimental group was assessed at 2 sessions (HFYB and breath awareness [BAW]) on alternate days. Hemodynamic changes were assessed using a functional near-infrared spectroscopy sensor placed over the forehead. Data were analyzed using repeated-measures analyses of variance followed by post hoc Bonferroni adjustment.ResultsA significant reduction was observed in oxy-Hb during and after HFYB on the left and right sides compared to values before. We also found a significant reduction in deoxy-Hb during and after the quiet sitting control session compared to pre-session values on left and right sides.ConclusionsThe decrease in oxy-Hb during and after HFYB suggests that there was no frontal activation during HFYB when practiced at the rate of 1.0 Hz.

Hemodynamic responses in rat brain during transcranial direct current stimulation: a functional near-infrared spectroscopy study.

In the present study, we monitored hemodynamic responses in rat brains during transcranial direct current stimulation (tDCS) using functional near-infrared spectroscopy (fNIRS). Seven rats received transcranial anodal stimulation with 200 μA direct current (DC) on their right barrel cortex for 10 min. The concentration changes of oxygenated hemoglobin (oxy-Hb) were continuously monitored during stimulation (10 min) and after stimulation (20 min). The trend of hemodynamic response changes was modeled using linear regression, and the relationship between incremental and decremental rates of oxy-Hb was investigated by correlation analysis. Our results showed that the oxy-Hb concentration was almost linearly increased and decreased during and after stimulation, respectively. In addition, a significant negative correlation (p < 0.05) was found between the rate of increase of oxy-Hb during stimulation and the rate of decrease of oxy-Hb after stimulation, indicating that the recovery time after tDCS may not depend on the total amount of hemodynamic changes in the stimulated brain area. Our results also demonstrated considerable individual variability in the rate of change of hemodynamic responses even with the same direct current dose to identical brain regions. This suggests that individual differences in tDCS after-effects may originate from intrinsic differences in the speed of DC stimulation "uptake" rather than differences in the total capacity of DC uptake, and thus the stimulation parameters may need to be customized for each individual in order to maximize tDCS after-effects.

Changes in cerebral blood oxygenation induced by active standing test in children with POTS and NMS.

Orthostatic dysregulation (OD) has been classified into subtypes by heart rate and blood pressure; however, the hemodynamics of brains have not yet been revealed. Therefore, we investigated changes in cerebral blood flow and oxygenation during an active standing test to clarify the pathophysiology of two subtypes: postural tachycardia syndrome (POTS) and neurally mediated syncope (NMS). We studied 31 children (15 boys, 16 girls; mean age, 14.0 ± 1.7 years) who presented with OD at the Department of Pediatrics and Child Health, Nihon University School of Medicine between 2009 and 2011. OD was diagnosed using the Japanese clinical guidelines for juvenile orthostatic dysregulation. After a 10-min resting period in the supine position, patients were asked to quickly stand up and keep upright for 10 min. Cerebral blood flow and cerebral oxygenation were measured using transcranial Doppler sonography and near-infrared spectroscopy. POTS showed a significant decrease of oxy-Hb and resistance index (RI), suggesting transient ischemia with maintainable cerebral autoregulation. NMS showed a decrease of oxy-Hb and an increase of RI, suggesting ischemia and impairment of autoregulation.

Monitoring of filter patency during carotid artery stenting using near-infrared spectroscopy with high time-resolution.

We aimed to evaluate the usefulness of a newly developed, near-infrared spectroscopy (NIRS) device for monitoring hemodynamic changes during carotid artery stenting (CAS), as a means to detect filter obstruction due to distal embolism. We evaluated 16 patients with internal carotid artery (ICA) stenosis during the CAS procedure, using a NIRS system that can monitor not only changes in oxygenation of hemoglobin (Hb), but also the fluctuation of oxyhemoglobin (oxy-Hb) synchronized with heartbeat. The NIRS system detected a marked decrease of oxy-Hb and an increase of deoxyhemoglobin (deoxy-Hb) during ICA occlusion in patients without anterior cross circulation (ACC). Patients with ACC showed much smaller changes. The analysis of oxy-Hb fluctuation made it possible to detect occurrence of no-flow in the absence of Hb concentration changes. The amplitude of oxy-Hb fluctuation in the no/slow-flow group was significantly smaller than that in the normal-flow group. Our results indicate that the present high time-resolution NIRS device, which can measure oxy-Hb fluctuation, is superior to conventional NIRS for detecting filter obstruction.

Brain Activity Analysis for Sound Information Using Near-Infrared Spectroscopy

Human beings feel sound in various ways, depending on the environments. For instance, one hears car's engine sound while driving the car in the way different from while hearing it coming from outdoors inside the house. In this paper, the analysis of brain activation to various sounds was conducted using near-infrared spectroscopy. It turned out that the listening to music and uncomfortable sound decreased oxyHb in the prefrontal cortex. This reaction can be considered the response to the concentration on the sound. It also tuned out that there is a viewpoint that the decrease of oxyHb in a brain does not necessarily mean the the decline in the neural activity but the brain activation reaction. It is expected to qualify audio information extracted from these two regions and to serve the plan of sound design.

Recognition of Human Emotions from Cerebral Blood Flow Changes in the Frontal Region: A Study with Event-Related Near-Infrared Spectroscopy

The aim of this study is to develop a near-infrared spectroscopy (NIRS)-based system that recognizes pleasant and unpleasant human emotions based on cerebral blood flow (CBF) in order to understand the minds of patients whose brain function is severely impaired. The forehead region is easily accessible to NIRS measurements, whereas the role of the anterior prefrontal cortex (PFC) in the processing of emotion remains to be elucidated. Initially, using event-related NIRS we examined changes in oxygenated hemoglobin (oxy-Hb) as an indicator of regional CBF changes, which reflect brain activity directly related to emotions, but not to cognitive operations in the anterior frontal regions, during viewing affective pictures. The event-related potentials (ERPs), systemic blood pressure, and pulse rate were also measured simultaneously. The event-related analysis of changes in oxy-Hb for a 6 s-picture presentation period showed that very unpleasant emotion was accompanied by an increase in oxy-Hb in the bilateral ventrolateral PFCs, while very pleasant emotion was accompanied by a decrease in oxy-Hb in the left dorsolateral PFC. There were no significant differences in either ERPs or autonomic nervous system activities between the two emotional states. These findings suggest the possibility of recognizing patients' emotions from CBF changes.

Task-related brain activation during finger tapping and circle drawing monitored by fNIRS

The present study assessed brain activation measured by functional near-infrared spectroscopy (fNIRS) in which subjects perform two types of hand motor tasks: a finger tapping task and circle drawing task. For both experiments we employed 24-channel NIRS system covering the left hemisphere (Fig. 1(a)) The typical time course in oxygenated hemoglobin concentration (oxyHb) and deoxygenated hemoglobin concentration (deoxyHb) are shown in Fig. ​Fig.2.2. In finger-tapping tasks, four right-handed subjects performed right hand finger tapping at a rate of approx. 3 Hz paced by a metronome. Subjects performed 12 or 15 trials in which a trial consists of 10-s rest, 20-s finger tapping movement, 30-s rest and about 180-s of inter-task intervals. Changes in oxyHb and deoxyHb were measured at a sampling period of 130-ms. Also changes in the angular velocity of finger tapping, as a measure of the movement smoothness, were measured. Significant decrease in oxyHb and the angular velocity over time were observed, while those transitions further exhibited significant correlation at the channels covering SMA, the pre-motor area (PMA) and PFC (Fig. 1(b)). In circle drawing tasks, six right-handed subjects (males from 22 to 24 years old) performed circle drawing with right hand. Subjects were instructed to trace around a template circle at the frequency of 0.667 Hz. All subjects performed four trials where each consists of 10-s rest, 30-s circle drawing, 30-s rest and about 180-s intervals. We calculated a spatial error as a measure of task performance which is derived from the trajectory deviated from the template circle. We found that oxyHb as well as error rate were decreased over time, with those transitions further be significantly correlated at the channels covering PFC and M1 (Figure 1(c)). Figure 1 (a) Channel setups in fNIRS measurements. (b) Regional activations during finger tapping tasks. Colored area represents where changes in oxyHb were significantly correlated with the task-performance (i.e. tapping smoothness) in all subjects (red), all ... Figure 2 Typical time course of the hemoglobin concentration changes at channel 18 over the prefrontal cortex. (a) The result of finger tapping task at the first trial period (top) and the 15th trial period (bottom). (b) The result of circle drawing task at the ... In summary, this paper reports our empirical results using the two types of hand motor tasks. The experimental results indicated the task-related activity observed in NIRS signals. A previous fNIRS study using hand motor tasks showed similar results including decreased pattern of hemodynamics in SMA [1], whereas further investigation will be desired that may allows to estimate precise cortical functions reflecting motor behaviors.

Real‐time measurement of oxyhemoglobin concentration changes in the frontal micturition area: An fNIRS study

To explore brain activity in the frontal micturition area during natural bladder behavior. Five control subjects (one man and four women; mean age 61 years [38-70]) and four subjects with detrusor overactivity (all men; mean age 55 years [33-65]) were enrolled in the study. We performed real-time measurements of oxyhemoglobin concentration (oxy-Hb) changes in the frontal micturition area using functional near-infrared spectroscopy (fNIRS) in response to quasi-natural, continuous bladder filling, and voiding in a sitting position. In the control group the following results were obtained: (1) a slight increase of oxy-Hb before first sensation occurred, (2) there was a continuous increase of oxy-Hb during bladder filling to the point just after voiding began, (3) there was a continuous decrease of oxy-Hb after voiding, (4) in subjects who were unable to urinate, oxy-Hb also decreased after attempting to void, and (5) the area activated was the bilateral lateral prefrontal area, particularly Brodmann's areas 8, 10, and 46. In the detrusor overactivity group, (6) an increase of oxy-Hb before first sensation was rare and frontal cortical activation was weak, (7) at the moment detrusor overactivity appeared, fNIRS brain activity in the frontal cortex did not change significantly; and otherwise the results were almost the same as those in the control group. This study shows that the frontal micturition area is activated during natural bladder filling and voiding using fNIRS.

Brain Activity Evaluation Using Oxy-Hb by Difference in the Strength of Sound Stimulus

We carried out a psychological study involving physiological measurements. We used the VAS to research the feeling. The physiological factor measured was the oxy-Hb. It was found that an auditory stimulus of 70[dB] is more uncomfortable than auditory stimulus of 50[dB]. Furthermore, the decrease in oxy-Hb was greater for the auditory stimulus of 70[dB] as compared to the auditory stimulus of 50[dB]. This tendency was found in the center of the forehead (ch22-ch25). There was a difference between the brain activity for the auditory stimulus of 70[dB] and that for the auditory stimulus of 50[dB]. It was also found that the sound level affects the comfort level of humans. It is necessary to obtain additional details on the effects from physiological index to psychological index in a future study.

Insufficient sleep impairs driving performance and cognitive function

Cumulative sleep deprivation may increase the risk of psychiatric disorders, other disorders, and accidents. We examined the effect of insufficient sleep on cognitive function, driving performance, and cerebral blood flow in 19 healthy adults (mean age 29.2 years). All participants were in bed for 8h (sufficient sleep), and for <4h (insufficient sleep). The oxyhaemoglobin (oxyHb) level by a word fluency task was measured with a near-infrared spectroscopy recorder on the morning following sufficient and insufficient sleep periods. Wisconsin card sorting test, continuous performance test, N-back test, and driving performance were evaluated on the same days. The peak oxyHb level was significantly lower, in the left and right frontal lobes after insufficient sleep than after sufficient sleep (left: 0.25+/-0.13 vs. 0.74+/-0.33 mmol, P<0.001; right: 0.25+/-0.09 vs. 0.69+/-0.44 mmol, P<0.01). The percentage of correct responses on CPT after insufficient sleep was significantly lower than that after sufficient sleep (96.1+/-4.5 vs. 86.6+/-9.8%, P<0.05). The brake reaction time in a harsh-braking test was significantly longer after insufficient sleep than after sufficient sleep (546.2+/-23.0 vs. 478.0+/-51.2 ms, P<0.05). Whereas there were no significant correlations between decrease in oxyHb and the changes of cognitive function or driving performance between insufficient sleep and sufficient sleep. One night of insufficient sleep affects daytime cognitive function and driving performance and this was accompanied by the changes of cortical oxygenation response.

Quantitative study on cerebral blood volume determined by a near‐infrared spectroscopy during postural change in children

To investigate changes in cerebral blood volume during standing in healthy children with or without abnormal cardiovascular responses. We studied 53 children (age, 10-15 years). Cerebral oxygenated haemoglobin (oxy-Hb) and deoxygenated Hb (deoxy-Hb) were non-invasively and continuously measured using near-infrared spectroscopy (NIRS) (NIRO 300, Hamamatsu Photomedics, Shizuoka, Japan) during active standing. Beat-to-beat arterial pressure was monitored by Portapres. Of 49 children with complete data acquisition, 33 had a normal cardiovascular response to the test (Group I) and 16 showed an abnormal response (Group II); nine with instantaneous orthostatic hypotension, three with postural tachycardia syndrome, three with neutrally mediated syncope and one with delayed orthostatic hypotension. At the onset of standing, Group II showed a significantly larger fall of oxy-Hb than Group I did (-2.9 +/- 2.8 micromol/L vs. -6.4 +/- 7.2 micromol/L, respectively, p < 0.05). During min 1 to 7 of standing, with one exception, changes in oxy-Hb were normally distributed over the level of -4 micromol/L in Group I. Group II also showed a significantly marked decrease in oxy-Hb compared to Group I. Decreases in oxy-Hb were not correlated with blood pressure changes. This study shows that precise change in cerebral blood volume caused by orthostatic stress can be determined by NIRS in children in a quantitative manner of NIRS. Children with abnormal circulatory responses to standing showed a significant reduction of oxy-Hb compared with normal counterparts, suggesting impairment of cerebral autoregulation in these children.

Cerebral oxygenation declines despite maintained orthostatic tolerance after brief exposure to gravitational stress

We examined the effect of a single 120 s of exposure to +3 G z (head-to-foot inertial forces) centrifugation as orthostatic stress on cerebral oxygenation (oxy-Hb) and cerebral blood volume (CBV) changes in response to stand test, in order to relate the occurrence of altered cerebral oxygenation control to any increase in sympathetic activity. Frontal near-infrared spectroscopy and mean arterial blood pressure at brain level (MAP brain) were recorded in 14 subjects in supine and then in standing (10 min) position, before and after +3 G z centrifugation. The decrease in oxy-Hb (−7 ± 5 a.u. versus −27 ± 4 a.u., P < 0.001) and in CBV (−6 ± 10 a.u. versus −15 ± 8 a.u., P < 0.05) upon standing was more important after +3 G z centrifugation, with unchanged MAP brain (−8 ± 8 mmHg versus −3 ± 11 mmHg). Upon standing, the high-frequency component of heart rate was lower (1090 ± 460 ms 2 versus 827 ± 412 ms 2, P < 0.05) after +3 G z centrifugation. These findings suggest a downward shift in the static cerebral autoregulatory curve. We conclude that cerebral vasoconstriction might have occurred without centrally mediated increase in the entire peripheral sympathetic activity of the body.

Effects of blackcurrant anthocyanin intake on peripheral muscle circulation during typing work in humans

This double-blind, placebo-controlled, crossover study investigated the effect of blackcurrant anthocyanin (BCA) intake on peripheral circulation during rest and during typing work by using near-infrared spectroscopy (NIRS), and it also assessed improvement in shoulder stiffness caused by poor local circulation. In a resting circulation study, nine healthy male subjects took capsules of BCA at a dosage of 17 mg kg(-1) or placebo (isoenergetic sugar). NIRS was used to measure left forearm blood flow (FBF) following venous occlusion and muscle oxygen consumption following arterial occlusion prior to and hourly for 4 h after ingestion of BCA. Plasma anthocyanin concentration was measured prior to ingestion and 1, 2, and 4 h later. FBF increased significantly 2 h after BCA ingestion [BCA 1.22 (0.13)-fold increase relative to pre-values vs placebo 0.83 (0.06) of pre-values; P < 0.05] and then tended to increase for a further 3 h after ingestion [BCA 1.26 (0.15)-fold increase relative to pre-values vs placebo 0.82 (0.07) of pre-values; P = 0.078]. There was, however, no significant difference in muscle oxygen consumption between BCA and placebo intake at any time point. In a typing work study, 11 healthy subjects took capsules of BCA (7.7 mg kg(-1)) or placebo (isoenergetic sugar) daily for 2 weeks. The subjects then performed intermittent typing workload for 30 min in order to induce acute shoulder stiffness. During the workload, total hemoglobin and oxygenated hemoglobin (oxy-Hb) were determined using NIRS and myoelectric signals measured in the right trapezius muscle using electromyography (EMG). The viscoelasticity of the trapezius muscle was also evaluated using a muscle stiffness meter before and after the typing workload. BCA intake prevented the decrease in oxy-Hb significantly (P < 0.05), and also tended to alleviate the increase in root mean square (RMS) of the EMG during the typing workload, and also muscle stiffness after the workload. There was no improvement in typing performance with BCA intake. The results of this study suggest that intake of BCA may improve shoulder stiffness caused by typing work by increasing peripheral blood flow and reducing muscle fatigue.