Simultaneous Near-infrared Spectroscopy Research Articles

3T 31P/1H calf muscle coil for 1H and 31P MRI/MRS integrated with NIRS data acquisition.

Our aim was to design and build a 3T 31P/1H calf coil that is capable of providing both good 31P and 1H transmit and receive performance, as well as being capable of accommodating a near-infrared spectroscopy (NIRS) device for simultaneous NIRS data and MRI/MRS acquisition. In this work, we propose a new 3T 31P/1H birdcage combination design consisting of two co-centrically positioned birdcages on the same surface to maximize transmit efficiency and sensitivity for both nuclei. The 31P birdcage is a high-pass birdcage, whereas the 1H birdcage is a low-pass one to minimize coupling. The diameter of the 31P/1H birdcage combination was designed to be large enough to accommodate a NIRS device for simultaneous NIRS data and MRI/MRS acquisition. The one-layer coil structure of the birdcage combination significantly streamlines the mechanical design and coil assembly process. Full-wave simulation results show that the 31P and 1H are very well decoupled with each other, and the 1H and 31P SNR surpasses that of their standalone counterparts in the central area. Experiment results show that the inclusion of a NIRS device does not significantly affect the performance of the coil, thus enabling simultaneous NIRS and MRI readouts during exercise. Our findings demonstrate the feasibility and effectiveness of this dual-tuned coil design for combined NIRS and MRS measurements, offering potential benefits for studying metabolic and functional changes in the skeletal muscle in vivo.

Task-related brain activity in upper limb dystonia revealed by simultaneous fNIRS and EEG

ObjectiveThe aim of this study was to explore differences in brain activity and connectivity using simultaneous electroencephalography and near-infrared spectroscopy in patients with focal dystonia during handwriting and finger-tapping tasks. MethodsPatients with idiopathic right upper limb focal dystonia and controls were assessed by simultaneous near-infrared spectroscopy and electroencephalography during the writing and finger-tapping tasks in terms of the mu-alpha, mu-beta, beta and low gamma power and effective connectivity, as well as relative changes in oxyhemoglobin (oxy-Hb) and deoxyhemoglobin using a channel-wise approach with a mixed-effect model. ResultsPatients exhibited higher oxy-Hb levels in the right and left motor cortex and supplementary motor area during writing, but lower oxy-Hb levels in the left sensorimotor and bilateral somatosensory area during finger-tapping compared to controls. During writing, patients showed increased low gamma power in the bilateral sensorimotor cortex and less mu-beta and beta attenuation compared to controls. Additionally, patients had reduced connectivity between the supplementary motor area and the left sensorimotor cortex during writing. No differences were observed in terms of effective connectivity in either task. Finally, patients failed to attenuate the mu-alpha, mu-beta, and beta rhythms during the finger-tapping task. ConclusionsCortical blood flow and EEG spectral power differ between controls and dystonia patients, depending on the task. Writing increased blood flow and altered connectivity in dystonia patients, and it also decreased slow-band attenuation. Finger-tapping decreased blood flow and slow-band attenuation. SignificanceSimultaneous fNIRS and EEG may show relevant information regarding brain dynamics in movement disorders patients in unconstrained environments.

Cerebrovascular reactivity to carbon dioxide tension in newborns: data from combined time-resolved near-infrared spectroscopy and diffuse correlation spectroscopy.

Critically ill newborns are at risk of brain damage from cerebrovascular disturbances. A cerebral hemodynamic monitoring system would have the potential role to guide targeted intervention. To obtain, in a population of newborn infants, simultaneous near-infrared spectroscopy (NIRS)-based estimates of cerebral tissue oxygen saturation () and blood flow during variations of carbon dioxide tension () levels within physiologic values up to moderate permissive hypercapnia, and to examine if the derived estimate of metabolic rate of oxygen would stay constant, during the same variations. We enrolled clinically stable mechanically ventilated newborns at postnatal age without brain abnormalities at ultrasound. and blood flow index were measured using a non-invasive device (BabyLux), which combine time-resolved NIRS and diffuse-correlation spectroscopy. The effect of changes in transcutaneous on , cerebral blood flow (CBF), and cerebral metabolic rate of oxygen index () were estimated. Ten babies were enrolled and three were excluded. Median GA at enrollment was 39 weeks and median weight 2720 g. increased 0.58% (95% CI 0.55; 0.61, ), CBF 2% (1.9; 2.3, ), and 0.3% (0.05; 0.46, ) per mmHg increase in . BabyLux device detected -induced changes in cerebral and CBF, as expected. The small statistically significant positive relationship between and variation is not considered clinically relevant and we are inclined to consider it as an artifact.

A Wireless 2-Channel Layered EMG/NIRS Sensor System for Local Muscular Activity Evaluation.

A wireless 2-channel layered sensor system that enables electromyography (EMG) and near-infrared spectroscopy (NIRS) measurements at two local positions was developed. The layered sensor consists of a thin silver electrode and a photosensor consisting of a photoemitting diode (LED) or photodiode (PD). The EMG and NIRS signals were simultaneously measured using a pair of electrodes and photosensors for the LED and PD, respectively. Two local muscular activities are presented in detail using layered sensors. In the experiments, EMG and NIRS signals were measured for isometric constant and ramp contractions at each forearm using layered sensors. The results showed that local muscle activity analysis is possible using simultaneous EMG and NIRS signals at each local position.

Two-layered blood-lipid phantom and method to determine absorption and oxygenation employing changes in moments of DTOFs.

Near-infrared spectroscopy (NIRS) is an established technique for measuring tissue oxygen saturation (StO2), which is of high clinical value. For tissues that have layered structures, it is challenging but clinically relevant to obtain StO2 of the different layers, e.g. brain and scalp. For this aim, we present a new method of data analysis for time-domain NIRS (TD-NIRS) and a new two-layered blood-lipid phantom. The new analysis method enables accurate determination of even large changes of the absorption coefficient (Δµa) in multiple layers. By adding Δµa to the baseline µa, this method provides absolute µa and hence StO2 in multiple layers. The method utilizes (i) changes in statistical moments of the distributions of times of flight of photons (DTOFs), (ii) an analytical solution of the diffusion equation for an N-layered medium, (iii) and the Levenberg-Marquardt algorithm (LMA) to determine Δµa in multiple layers from the changes in moments. The method is suitable for NIRS tissue oximetry (relying on µa) as well as functional NIRS (fNIRS) applications (relying on Δµa). Experiments were conducted on a new phantom, which enabled us to simulate dynamic StO2 changes in two layers for the first time. Two separate compartments, which mimic superficial and deep layers, hold blood-lipid mixtures that can be deoxygenated (using yeast) and oxygenated (by bubbling oxygen) independently. Simultaneous NIRS measurements can be performed on the two-layered medium (variable superficial layer thickness, L), the deep (homogeneous), and/or the superficial (homogeneous). In two experiments involving ink, we increased the nominal µa in one of two compartments from 0.05 to 0.25 cm-1, L set to 14.5 mm. In three experiments involving blood (L set to 12, 15, or 17 mm), we used a protocol consisting of six deoxygenation cycles. A state-of-the-art multi-wavelength TD-NIRS system measured simultaneously on the two-layered medium, as well as on the deep compartment for a reference. The new method accurately determined µa (and hence StO2) in both compartments. The method is a significant progress in overcoming the contamination from the superficial layer, which is beneficial for NIRS and fNIRS applications, and may improve the determination of StO2 in the brain from measurements on the head. The advanced phantom may assist in the ongoing effort towards more realistic standardized performance tests in NIRS tissue oximetry. Data and MATLAB codes used in this study were made publicly available.

Effects of Posture and Walking on Tibial Vascular Hemodynamics Before and After 14 Days of Head-Down Bed Rest.

Human skeletal hemodynamics remain understudied. Neither assessments in weight-bearing bones during walking nor following periods of immobility exist, despite knowledge of altered nutrient-artery characteristics after short-duration unloading in rodents. We studied 12 older adults (8 females, aged 59 ± 3 years) who participated in ambulatory near-infrared spectroscopy (NIRS) assessments of tibial hemodynamics before (PRE) and after (POST) 14 days of head-down bed rest (HDBR), with most performing daily resistance and aerobic exercise countermeasures during HDBR. Continual simultaneous NIRS recordings were acquired over the proximal anteromedial tibial prominence of the right lower leg and ipsilateral lateral head of the gastrocnemius muscle during supine rest, walking, and standing. During 10 minutes of walking, desaturation kinetics in the tibia were slower (time to 95% nadir values 125.4 ± 56.8 s versus 55.0 ± 30.1 s, p = 0.0014). Tibial tissue saturation index (TSI) immediately fell (-9.9 ± 4.55) and did not completely recover by the end of 10 minutes of walking (-7.4 ± 6.7%, p = 0.027). Upon standing, total hemoglobin (tHb) kinetics were faster in the tibia (p < 0.0001), whereas HDBR resulted in faster oxygenated hemoglogin (O2Hb) kinetics in both tissues (p = 0.039). After the walk-to-stand transition, changes in O2Hb (p = 0.0022) and tHb (p = 0.0047) were attenuated in the tibia alone after bed rest. Comparisons of NIRS-derived variables during ambulation and changes in posture revealed potentially deleterious adaptations of feed vessels after HDBR. We identify important and novel tibial hemodynamics in humans during ambulation before and after bed rest, necessitating further investigation. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

A Wireless Multi-Layered EMG/MMG/NIRS Sensor for Muscular Activity Evaluation.

A wireless multi-layered sensor that allows electromyography (EMG), mechanomyography (MMG) and near-infrared spectroscopy (NIRS) measurements to be carried out simultaneously is presented. The multi-layered sensor comprises a thin silver electrode, transparent piezo-film and photosensor. EMG and MMG measurements are performed using the electrode and piezo-film, respectively. NIRS measurements are performed using the photosensor. Muscular activity is then analyzed in detail using the three types of data obtained. In experiments, the EMG, MMG and NIRS signals were measured for isometric ramp contraction at the forearm and cycling exercise of the lateral vastus muscle with stepped increments of the load using the layered sensor. The results showed that it was possible to perform simultaneous EMG, MMG and NIRS measurements at a local position using the proposed sensor. It is suggested that the proposed sensor has the potential to evaluate muscular activity during exercise, although the detection of the anaerobic threshold has not been clearly addressed.

Relationship Between Brain Tissue Oxygen and Near-Infrared Spectroscopy in Patients with Nontraumatic Subarachnoid Hemorrhage.

Continuous monitoring of cerebral oxygenation is one of the diagnostic tools used in patients with brain injury. Direct and invasive measurement of cerebral oxygenation with a partial brain oxygen pressure (PbtO2) probe is promising but invasive. Noninvasive assessment of regional transcranial oxygen saturation using near-infrared spectroscopy (NIRS) may be feasible. The aim of this study was to evaluate the interchangeability between PbtO2 and NIRS over time in patients with nontraumatic subarachnoid hemorrhage. This retrospective study was performed in a neurocritical care unit. Study participants underwent hourly PbtO2 and NIRS measurements over 72h. Temporal agreement between markers was described by their pointwise correlation. A secondary analysis assessed the structure of covariation between marker trajectories using a bivariate linear mixed model. Fifty-one patients with subarachnoid hemorrhage were included. A total of 3362 simultaneous NIRS and PbtO2 measurements were obtained. The correlation at each measurement time ranged from - 0.25 to 0.25. The global correlation over time was - 0.026 (p = 0.130). The bivariate linear mixed model confirmed the lack of significant correlation between the PbtO2 and NIRS measurements at follow-up. NIRS was unable to detect PbtO2 values below 20mm Hg (area under the receiver operating characteristic curve 0.539 [95% confidence interval 0.536-0.542]; p = 0.928), and percentage changes in NIRS were unable to detect a decrease in PbtO2 ≥ 10% (area under the receiver operating characteristic curve 0.615 [95% confidence interval 0.614-0.616]; p < 0.001). PbtO2 and NIRS measurements were not correlated. There is no evidence that NIRS could be a substitute for PbtO2 monitoring in patients with nontraumatic subarachnoid hemorrhage.

Simultaneous measurement under resting-state of autonomic nervous activity and brain activity by near-infrared spectroscopy alone

Near-infrared spectroscopy (NIRS) is widely used for brain-function imaging, but the raw signal also encompasses various other physiological factors such as heartbeat. In this study, we aimed to extract heartbeat-related signals from the NIRS signal and evaluate autonomic nervous activity and brain activity simultaneously. For that purpose, simultaneous NIRS and electrocardiogram (ECG) datasets were acquired for 10 healthy volunteers, and the heart-rate intervals obtained from each dataset were compared. We also investigated factors which could affect the extrication of heartbeat-related signals from NIRS data, such as the number of NIRS channels, type of NIRS signal, and resampling interval of NIRS data. We found that the heartbeat-related signals could be effectively extracted using total hemoglobin data by averaging all channels (52 channels) after band-pass filtering and upsampling to the same 4 msec (250 Hz) as the ECG sampling interval, which showed a high correlation with ECG R-R intervals. We also found that indicators of autonomic nervous activity could be calculated with NIRS data and had a high correlation with those calculated from ECG data. Despite its simplicity, our method demonstrates the possibility of analyzing brain activity while also considering autonomic nervous activity using NIRS data only.

Correlation of Near-Infrared Spectroscopy Oximetry and Corresponding Venous Oxygen Saturations in Children with Congenital Heart Disease.

Invasive and non-invasive monitoring allow for early detection of hemodynamic compromise, facilitating timely intervention and avoidance of further decline. While venous oximetry is useful for assessing the adequacy of systemic oxygen delivery (DO2), it is most often intermittent, invasive, and costly. Near-infrared spectroscopy (NIRS) oximetry allows for the non-invasive estimation of the adequacy of DO2. We assessed the correlation between cerebral NIRS oximetry and superior vena cava (SVC) and jugular venous (JV) oxygen saturations and between renal NIRS oximetry and inferior vena cava (IVC) oxygen saturations. Systematic review of the literature was conducted to identify studies with data regarding near-infrared spectroscopy and venous saturation. The PubMed, EMBASE, Medline, and Cochrane databases were queried using the following terms in isolation and various combinations: "congenital heart disease," "near infrared spectroscopy," "venous saturation," and "pediatric." Pediatric studies in which simultaneous NIRS oximetry and corresponding venous oxygen saturations were simultaneously collected after cardiac surgery or catheterization were identified. Data were pooled from these studies to analyze the correlation between NIRS oximetry and the corresponding venous oxygen saturations. A total of 16 studies with 613 patients were included in the final analyses. Data were present to compare cerebral and renal NIRS oximetry with corresponding venous oxygen saturation. Cerebral NIRS and SVC and JV oxygen saturations and renal NIRS and IVC oxygen saturations demonstrated strong degrees of correlation (r-value 0.70 for each). However, cerebral NIRS and IVC oxygen saturation had a week degree of correlation (r-value of 0.38). Pooled analyses demonstrate that cerebral NIRS oximetry correlates strongly with SVC or JV oxygen saturation while renal NIRS oximetry correlates strongly with IVC oxygen saturations. A weak correlation was noted between cerebral NIRS oximetry and IVC oxygen saturations.

Evaluation of the relationship between NIRS (near-infrared spectroscopy) and optic nerve sheath diameter measurement in children with increased intracranial pressure: a pilot study

BackgroundThe increased intracranial pressure (ICP) syndrome may emerge depending on many different neurological factors and the early diagnosis and treatment are important for the prevention of neurologic damage and related mortality. In recent years, the follow-up of increased ICP with non-invasive methods has been rising. In this study, our objective was to determine the significance and any possible correlation between Optic Nerve Sheath Diameter (ONSD) and Near Infrared Spectroscopy (NIRS) in children with increased ICP.MethodsPatients who were hospitalized in our pediatric ICU at Çukurova University Medical Faculty between June 2018 and June 2019 due to the suspicion of increased ICP were included in this study. The demographic characteristics of patients, diagnosis at admission, results of the cranial CT and MRI examinations, and results of the simultaneous ONSD and NIRS measurements were recorded.ResultsA total of 36 patients were included in our study. With respect to the diagnosis, non-traumatic causes were at the forefront in 30 patients (83.3%), and the most common causes were meningoencephalitis (n = 9; 25%) and non-traumatic bleeding (n = 7; 19.4%). Six of the patients were under the age of one year (16.7%), and the mean values of ONSD and NIRS were 4.8 ± 0.7 mm and 71.1 ± 12.4% respectively in this group. Fourteen patients were in the one to ten year age group and the mean values of ONSD and NIRS were 6.1 ± 0.6 mm and 72.7 ± 9.3% respectively. Sixteen patients were over ten years of age (44.4%), and the mean values of ONSD and NIRS were 5.6 ± 0.7 mm and 74.2 ± 16% respectively. There was no correlation between the ONSD and NIRS values (r:0.307; p = 0.068).ConclusionOur study showed that ONSD measurements were helpful in children with increased ICP and reflected the increase in ICP. However, our study also demonstrated that ONSD was not in correlation with the NIRS monitoring. We believe that there is a need for further studies focused on the use of ONSD and NIRS in the monitoring of increased ICP.

An Elusive Prize: Transcutaneous Near InfraRed Spectroscopy (NIRS) Monitoring of the Liver.

Introduction: We postulate a relationship between a transcutaneous hepatic NIRS measurement and a directly obtained hepatic vein saturation. If true, hepatic NIRS monitoring (in conjunction with the current dual-site cerebral-renal NIRS paradigm) might increase the sensitivity for detecting shock since regional oxygen delivery changes in the splanchnic circulation before the kidney or brain. We explored a reliable technique for hepatic NIRS monitoring as a prelude to rigorously testing this hypothesis. This proof-of-concept study aimed to validate hepatic NIRS monitoring by comparing hepatic NIRS measurements to direct hepatic vein samples obtained during cardiac catheterization.Method: IRB-approved prospective pilot study of hepatic NIRS monitoring involving 10 patients without liver disease who were already undergoing elective cardiac catheterization. We placed a NIRS monitor on the skin overlying liver during catheterization. Direct measurement of hepatic vein oxygen saturation during the case compared with simultaneous hepatic NIRS measurement.Results: There was no correlation between the Hepatic NIRS values and the directly measured hepatic vein saturation (R = −0.035; P = 0.9238). However, the Hepatic NIRS values correlated with the cardiac output (R = 0.808; P = 0.0047), the systolic arterial blood pressure (R = 0.739; P = 0.0146), and the diastolic arterial blood pressure (R = 0.7548; P = 0.0116).Conclusions: Using the technique described, hepatic NIRS does not correlate well with the hepatic vein saturation. Further optimization of the technique might provide a better measurement. Hepatic NIRS does correlate with cardiac output and thus may still provide a valuable additional piece of hemodynamic information when combined with other non-invasive monitoring.

A Hybrid BCI Using Singular Value Decomposition Values of the Fast Walsh–Hadamard Transform Coefficients

One of the main goals of a brain computer interface (BCI) is to enable a communication channel between the brain and electronic devices by converting neural activity into control commands either for devices or applications. Because of the excellent temporal resolution, low set-up cost, and non-invasive nature, BCI systems generally use electroencephalography (EEG) for an input signal. However, EEG suffers from poor spatial resolution, and it is contaminated by various external and internal artifacts such as environmental magnetic noises and body movements. These limitations directly affect the performance of the EEG-based BCI system, and it might not work at the desired level. On the other hand, near-infrared spectroscopy (NIRS) has an advantage of relative robustness against body movements and electrical artifacts. Additionally, it is also a promising neural signal recording method which provides good spatial resolution. In this study, we particularly focused on compensating the limitations of EEG-based BCI system by adding simultaneous NIRS modality features. In order to show the effectiveness of our method, we used an open-access dataset, which was recorded from 29 subjects with simultaneous EEG-NIRS system during the imagination of opening and closing either a left-or right-hand. The features were extracted by calculating the singular value decomposition values of the Fast Walsh-Hadamard Transform coefficients. Afterward, the k-nearest neighbor algorithm was performed to classify the features. The performance of the proposed method was evaluated in terms of classification accuracy and kappa value metrics. The achieved results showed that combining a hybrid BCI system with EEG-NIRS modalities can enhance the performance of a BCI by 6.75% compared to the single-modality solution of EEG.

Cerebral and peripheral tissue oxygenation in stable neonates: Absent influence of cardiac function.

AimCardiac function is a major factor for tissue perfusion and therefore may affect the tissue oxygen saturation. Aim was to analyse possible associations between cardiac function parameters and cerebral and peripheral tissue oxygenation in neonates on the first day after birth.MethodsFor the present study, we analysed secondary outcome parameters of a previously performed prospective single centre observational study. The prospective study was conducted at the Medical University of Graz, Austria between September 2011 and June 2013. We included preterm and term neonates who were admitted to the neonatal intensive care unit and in whom simultaneous near‐infrared spectroscopy measurements and echocardiography were obtained on the first day after birth. Cardiac function parameters were correlated to cerebral and peripheral tissue oxygen saturation and cerebral and peripheral fractional tissue oxygen extraction at the time of echocardiography.ResultsA total of 60 neonates of whom 47 were preterm and 13 were term (median gestational age: 34; IQR 33‐35 weeks, mean birth weight: 2276 ± 774 grams) were included. There were no statistically significant correlations between cardiac function parameters and regional tissue oxygenation parameters.ConclusionIn the present study, we found no correlation between regional tissue oxygenation and parameters of cardiac function in cardio‐circulatory stable neonates on the first day after birth.

Changes in cerebral oxygenation and cerebral blood flow during hemodialysis – A simultaneous near-infrared spectroscopy and positron emission tomography study

Near-infrared spectroscopy (NIRS) is used to monitor cerebral tissue oxygenation (rSO2) depending on cerebral blood flow (CBF), cerebral blood volume and blood oxygen content. We explored whether NIRS might be a more easy applicable proxy to [15O]H2O positron emission tomography (PET) for detecting CBF changes during hemodialysis. Furthermore, we compared potential determinants of rSO2 and CBF. In 12 patients aged ≥ 65 years, NIRS and PET were performed simultaneously: before (T1), early after start (T2), and at the end of hemodialysis (T3). Between T1 and T3, the relative change in frontal rSO2 (ΔrSO2) was −8 ± 9% (P = 0.001) and −5 ± 11% (P = 0.08), whereas the relative change in frontal gray matter CBF (ΔCBF) was −11 ± 18% (P = 0.009) and −12 ± 16% (P = 0.007) for the left and right hemisphere, respectively. ΔrSO2 and ΔCBF were weakly correlated for the left (ρ 0.31, P = 0.4), and moderately correlated for the right (ρ 0.69, P = 0.03) hemisphere. The Bland-Altman plot suggested underestimation of ΔCBF by NIRS. Divergent associations of pH, pCO2 and arterial oxygen content with rSO2 were found compared to corresponding associations with CBF. In conclusion, NIRS could be a proxy to PET to detect intradialytic CBF changes, although NIRS and PET capture different physiological parameters of the brain.

Limited value of temporo-parietal hemodynamic signals in an optical-electric auditory brain-computer interface

Objective. Auditory brain-computer interfaces (BCIs) have gained attention recently due to their potential applicability to severely disabled individuals without functional vision. However, auditory BCIs currently achieve lower accuracies than their visual counterparts, and most have exploited only one type of brain measurement. Recent evidence suggests that the combination of electrical and optical measurements can enhance classification accuracies in motor imagery-based BCIs. The potential of this bimodal combination for auditory BCIs remains unexplored. Approach. We investigated the complementarity of near-infrared spectroscopy (NIRS) and electroencephalography (EEG) in discriminating between attentive and non-attentive behaviours to auditory stimuli. Simultaneous NIRS and EEG signals were recorded from 11 typically developed participants while performing an auditory oddball streaming task. Main Results. Considering neural responses to oddballs during the entire span of a trial, average classification accuracies of 77.43+/−9.6% and 80.7+/−9.5% were achieved using combined EEG and NIRS signal and the EEG-only signal respectively. The combined EEG-NIRS classification accuracy was significantly lower than the EEG-only accuracy in five participants. However, when considering EEG responses to the first oddball within each trial, we found that the inclusion of NIRS activities from the complete task period significantly improved classification accuracies for 2 participants. Significance. Our findings suggest that the consolidation of EEG (midline) and NIRS (temporo-parietal) signals offers limited value beyond an EEG-exclusive approach when decoding prolonged auditory attention-demanding tasks. Future efforts should focus on identifying the optimal time window for the analysis of EEG and NIRS signals to delineate conditions under which the BCI may afford a practical advantage over the EEG-exclusive approach.

Gender differences in brain networks during verbal Sternberg tasks: A simultaneous near-infrared spectroscopy and electro-encephalography study.

Gender differences in psychological processes have been of great interest in a variety of fields including verbal fluency, emotion processing and working memory. Previous studies suggested that women outperform men in verbal working memory (VWM). However, the inherent mechanisms are still unclear. To obtain a deeper insight into the gender differences in brain networks in VWM, this study used near-infrared spectroscopy (NIRS) and electro-encephalography (EEG) simultaneously to investigate gender-related brain networks during verbal Sternberg tasks. NIRS results confirmed that women surpass men in VWM from the perspective of both brain activation and connectivity. Results of EEG (effective connectivity and event-related spectral power) showed that men tend to use a more visuospatial strategy to encode memory. In addition, novel analysis methods of brain networks can provide useful information about the gender specifics of brain functions. Gender-related pseudo-color maps constructed from all channels of average HbO2 activity during low- and high-load tasks (from 0 to 6 seconds after beginning).

FV 10. Motor imagery supported by neurofeedback: Age-related changes in EEG and fNIRS lateralization patterns

Motor imagery (MI) supported by neurofeedback has been suggested as a promising add-on therapy to facilitate motor recovery after stroke. Though the main target group for such an intervention are elderly patients, research so far is largely focused on young, healthy adults. We therefore examined in two experiments the influence of age on the neural correlates of motor imagery (MI) in a real-time electroencephalogram (EEG) neurofeedback framework. In a first experiment MI-induced activity was studied in MI and neurofeedback naive young ( N = 39; 18–30 years) and elderly ( N = 36; >55 years) healthy adults. MI was supported by EEG feedback, and feedback was based on features extracted from the mu and beta frequency bands. Electromyogram (EMG) data were recorded concurrently to control for executed movements. During MI the group of older participants was characterized by a significantly reduced lateralization of EEG event-related desynchronization (ERD), mainly due to stronger ipsilateral ERD, and, in consequence, reduced classification accuracies. EEG-based neurofeedback resulted in a task-related activity increase irrespective of age. Aim of the second experiment was to replicate and validate these results. To this end, EEG was combined with simultaneous functional near-infrared spectroscopy (fNIRS). MI-induced activity was studied in a new sample of MI and neurofeedback naive young ( N = 19; 18–30 years) and elderly ( N = 18; >55 years) healthy adults. As before, MI was supported by EEG feedback based on features extracted from mu and beta frequency bands and EMG data were recorded concurrently to control for executed movements. The observation of a reduced lateralization due to stronger ipsilateral ERD could be replicated. Furthermore, fNIRS deoxygenated haemoglobin concentration changes confirmed this less lateralized pattern in the elderly. For both age groups the EEG-based neurofeedback resulted in a task-related increase in ERD and fNIRS activity. The reduction of lateralized brain activity during MI in the elderly is in good agreement with previous research showing similar age-related changes during MI and other cognitive tasks. This finding is in line with the general view that compensatory processes are recruited to counteract neurodegenerative changes during healthy ageing. However, these age-related changes did not compromise the responsiveness to neurofeedback. We therefore conclude that the potential benefit of a neurofeedback supported modulation of brain activity is preserved in the elderly.

Mapping Cortical Responses to Somatosensory Stimuli in Human Infants with Simultaneous Near-Infrared Spectroscopy and Event-Related Potential Recording.

Near-infrared spectroscopy (NIRS) and electroencephalography (EEG) have recently provided fundamental new information about how the newborn brain processes innocuous and noxious somatosensory information. However, results derived independently from these two techniques are not entirely consistent, raising questions about the relationship between hemodynamic and electrophysiological responses in the study of touch and pain processing in the newborn. To address this, we have recorded NIRS and EEG responses simultaneously for the first time in the human infant following noxious (time-locked clinically required heel lances) and innocuous tactile cutaneous stimulation in 30 newborn infants. The results show that both techniques can be used to record quantifiable and distinct innocuous and noxious evoked activity at a group level in the newborn cortex. Noxious stimulation elicits a peak hemodynamic response that is 10-fold larger than that elicited by an innocuous stimulus (HbO2: 2.0 vs 0.3 µm) and a distinct nociceptive-specific N3P3 waveform in electrophysiological recordings. However, a novel single-trial analysis revealed that hemodynamic and electrophysiological responses do not always co-occur at an individual level, although when they do (64% of noxious test occasions), they are significantly correlated in magnitude. These data show that, while hemodynamic and electrophysiological touch and pain brain activity in newborn infants are comparable in group analyses, important individual differences remain. These data indicate that integrated and multimodal brain monitoring is required to understand central touch and pain processing in the newborn.

Brain Maturity and Variation of Oxygen Extraction in Premature Infants.

Objectives The ability of the premature brain to extract and use oxygen has not been studied adequately. This study aimed to determine factors that influence fractional tissue oxygen extraction (FTOE) of the brain in premature infants using near-infrared spectroscopy (NIRS) and pulse oximetry. Study Design We prospectively studied FTOE in very low birth weight (BW) infants (< 1,500 g and ≤ 34 weeks' gestation). Factors affecting FTOE and its variability were examined using bivariate and linear regression models. FTOE variability was measured on two scales: short scales (3-20 seconds) and long scales (20-150 seconds). Results We examined 147 simultaneous NIRS and pulse oximetry recordings that were collected from 72 premature infants (gestational age [GA] = 28 weeks and BW = 1,036 g). In regression models, average FTOE correlated negatively with hemoglobin (Hb) and increased significantly in patients with severe intraventricular hemorrhage/periventricular leukomalacia. Both FTOE short- and long-scale variabilities correlated negatively with GA and positively with postnatal age (PNA). Moreover, FTOE long-scale variability was significantly reduced in infants supported with invasive ventilation. Conclusions In premature infants, cerebral oxygen extraction increased with reduced Hb and severe brain injury. Variability in oxygen extraction showed differential changes with GA and PNAs and was affected by invasive ventilation.