Real-time continuous neuromonitoring combines transcranial cerebral Doppler with near-infrared spectroscopy cerebral oxygen saturation during total aortic arch replacement procedure: a pilot study

The purpose of this investigation was to use combined transcranial cerebral Doppler (TCD) and near-infrared spectroscopy cerebral oxygen saturation (NIRS) during total aortic arch replacement (TAAR) to monitor middle cerebral artery blood flow velocity and regional cerebral oximetry (rSO(2)) changes to provide a clinical basis for protective measures that may decrease injury of the central nervous system. Consecutive 12 adult patients underwent deep hypothermic circulatory arrest (DHCA) and antegrade selective cerebral perfusion (ASCP) during TAAR. A TCD probe was placed at the temporal windows after induction of anesthesia and the NIRS probe placed on the forehead of patients to collect perioperative, intraoperative, and postoperative hemodynamic parameters, and cerebral blood flow (CBF) and rSO(2) during cardiopulmonary bypass (CPB). In this retrospective case series, all patients survived, and there were no postoperative neurologic complications. There was no significant correlation between the mean arterial pressure and rSO(2). The middle cerebral artery mean velocity (VmMCA) and rSO(2) were significantly correlated, and main pump flow significantly correlated with rSO(2). After ASCP, VmMCA, rSO(2), and venous oxygen saturation were significantly lower than before ASCP, but VmMCA and rSO(2) returned to pre-CPB levels postoperatively. After off pump, the flow of ASCP showed a significant positive correlation with VmMCA and rSO(2). During DHCA when ASCP flow was lower than 5 ml/kg/min, TCD could not detect the MCA blood flow signal. When the flow of ASCP was above keeping around 10 ml/kg/min, MCA CBF velocity was maintained and rSO(2) > 45%. The combination of TCD and NIRS can be effective in monitoring brain function during DHCA with ASCP and may provide a guide for decreasing brain injury during the TAAR procedure.     

Reduced prefrontal activation during Tower of London in first-episode schizophrenia: A multi-channel near-infrared spectroscopy study

Cognitive impairments are considered as a core feature of schizophrenia and have been reported in associated with dysfunction of the prefrontal cortex (PFC). The Tower of London (TOL) task is a widely used neuropsychological test to assess the planning ability and the PFC function. In the present study, we examined functional changes in the PFC of 40 first-episode schizophrenia patients and 40 age- and gender-matched healthy controls by means of multi-channel Near-infrared spectroscopy (NIRS) during performance of the TOL task. NIRS is a noninvasive optical method that can measure relative changes in oxygenated ([oxy-Hb]) and deoxygenated ([deoxy-Hb]) hemoglobin in cortical tissue. Compared to the healthy controls, schizophrenia patients exhibited a significant decreased activation in the left PFC and poorer TOL performance. The results confirm the functional deficits of the PFC and impaired planning ability in first-episode schizophrenia patients and suggest that NIRS may be a useful clinical tool for evaluating PFC activation in psychiatric disorders.     

Intersubject variability of near-infrared spectroscopy signals during sensorimotor cortex activation

We investigate the intersubject signal variability of near-infrared spectroscopy (NIRS), which is commonly used for noninvasive measurement of the product of the optical path length and the concentration change in oxygenated hemoglobin (DeltaC'oxy) and deoxygenated hemoglobin (DeltaC'deoxy) and their sum (DeltaC'total) related to human cortical activation. We do this by measuring sensorimotor cortex activation in 31 healthy adults using 24-measurement-position near-infrared (NIR) topography. A finger-tapping task is used to activate the sensorimotor cortex, and significant changes in the hemisphere contralateral to the tapping hand are assessed as being due to the activation. Of the possible patterns of signal changes, 90% include a positive DeltaC'oxy, 76% included a negative DeltaC'deoxy, and 73% included a positive DeltaC'total. The DeltaC'deoxy and DeltaC'total are less consistent because of a large intersubject variability in DeltaC'deoxy; in some cases there is a positive DeltaC'deoxy. In the cases with no positive DeltaC'oxy in the contralateral hemisphere, there are cases of other possible changes for either or both hemispheres and no cases of no change in any hemoglobin species in either hemisphere. These results suggest that NIR topography is useful for observing brain activity in most cases, although intersubject signal variability still needs to be resolved.     

Time courses of brain activation and their implications for function: a multichannel near-infrared spectroscopy study during finger tapping

The time courses of brain activation were monitored during a finger tapping task using multichannel near-infrared spectroscopy with a time resolution of 0.1s in 30 healthy volunteers. Task-induced brain activations were demonstrated as significant increases in oxygenated hemoglobin concentration ([oxy-Hb]) in a broad area around the motor cortex and significant decreases in deoxygenated hemoglobin concentration ([deoxy-Hb]) in a more restricted area, with a large degree of activation in the contralateral hemisphere. The time courses of the [oxy-Hb] changes varied depending on channel location: sustained activation across the task period in the motor cortex, transient activation during the initial segments of the task period in the somatosensory cortex, and accumulating activation along the task period in the frontal lobe. These characteristics are assumed to reflect the functional roles of the brain structures during the task period, that is, the execution, sensory monitoring, and maintenance of finger tapping.     

经颅电刺激对大鼠脑梗死后运动功能恢复的影响

目的 :观察经颅皮层电刺激治疗对大鼠脑梗死后运动功能恢复的作用。方法 :选择12 0只SD成年雄性大鼠制作大脑中动脉闭塞 (MCAO)模型 ,将大鼠随机分为治疗组和对照组各 6 0只 ,治疗组在术后 3天给予经颅电刺激治疗 ,对照组术后不进行治疗 ,于术后第 1、2、3、4、5、6周末 ,分别以横木行走试验 (BWT)及运动诱发电位为指标评价大鼠运动功能恢复情况。结果 :经颅磁刺激治疗的大鼠 ,运动功能较对照组明显改善 (P <0 .0 1)。第 6周末治疗组患侧MEP波幅与潜伏期基本恢复正常 ,而对照组患侧MEP波幅仅恢复到 73.5 % ,潜伏期仍有所延长 ,两组相比有显著差异 (P <0 .0 5 )。结论 :经颅电刺激可以促进急性脑梗死大鼠瘫痪肢体运动功能的恢复 ,其机理可能与电刺激直接兴奋大脑皮层的运动中枢有关     

强迫症患者言语流畅性任务脑激活时间特征的近红外光谱成像研究

目的:探讨强迫症患者言语流畅性任务(VFT)下前额叶及颞叶激活的时间特征。方法:选取70例符合DSM-IV强迫症诊断标准的患者和70例正常对照,应用52通道的近红外光谱成像技术(NIRS)测评完成VFT时前额叶及颞叶血流的变化。比较两组完成任务时氧合血红蛋白(oxy-Hb)、脱氧血红蛋白(deoxy-Hb)及总血红蛋白(total-Hb)浓度达峰时间的差异。结果:与正常对照组相比,强迫症患者52个通道oxy-Hb、deoxy-Hb和total-Hb浓度的平均达峰时间明显延迟[(61±12)s vs.(52±11)s,(64±10)s vs.(58±10)s,(59±13)s vs.(51±13)s,均P<0.01]。强迫症组oxy-Hb和total-Hb在眶额叶、额极、前额下回、颞中回及颞上回等脑区达峰时间明显延迟(均P<0.05,FDR校正)。结论:强迫症患者执行言语流畅性任务时前额叶及颞叶皮质激活可能有延迟。     

Within-subject reproducibility of near-infrared spectroscopy signals in sensorimotor activation after 6 months

Near-infrared spectroscopy (NIRS) can measure the product of the optical path length and the concentration change in oxygenated hemoglobin (DeltaC'oxy), deoxygenated hemoglobin (DeltaC'deoxy), and their sum (DeltaC'total) in the human cerebral cortex, and it has been used for noninvasive investigation of human brain functions. We evaluate the within-subject reproducibility of the NIRS signals by repeated measurement of the sensorimotor cortex in healthy adults taken over a period of about 6 months using near-infrared (NIR) topography. The maximum signal amplitudes and the location of activation centers are compared between two sessions for each subject. The signal amplitudes vary between sessions and no consistent tendency in the changes is found among subjects. However, the distance between the activation centers identified in two sessions is relatively small, within 20 mm on average across subjects, which is comparable to the smallest distance between measurement positions in the NIR topography (21 mm). Moreover, within-subject comparisons of signal time courses show high correlation coefficients (>0.8) between the two sessions. This result, demonstrating a high within-subject reproducibility of the temporal information in NIRS signals, particularly contributes to the development of a new application of NIRS.     

Deactivation and activation of left frontal lobe during and after low-frequency repetitive transcranial magnetic stimulation over right prefrontal cortex: A near-infrared spectroscopy study

The effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) over the right frontal lobe on the function of the left frontal lobe were examined by near-infrared spectroscopy (NIRS) in eleven healthy subjects. rTMS applied 5 cm anterior to the motor cortex at 1 Hz and approximately 50% of the motor threshold intensity (MT) for 60 s resulted in a significantly larger decrease in the concentration of oxygenated hemoglobin ([oxy-Hb]) during the stimulation period followed by a significantly larger increase in [oxy-Hb] and a smaller decrease in the concentration of deoxygenated hemoglobin ([deoxy-Hb]) during the poststimulation baseline period than sham stimulation. These findings are interpreted as demonstrating the deactivation and activation of the left frontal cortex during and after rTMS of the right frontal cortex, respectively. If replicated in depressed patients, NIRS can be employed for monitoring rTMS effects as brain [Hb] changes in vivo, and may be helpful for determining therapeutic parameters of rTMS for individual patients.     

Evaluation of cerebral ischemia using near-infrared spectroscopy with oxygen inhalation

ABSTRACT. Conventional methods presently used to evaluate cerebral hemodynamics are invasive, require physical restraint, and employ equipment that is not easily transportable. Therefore, it is difficult to take repeated measurements at the patient's bedside. An alternative method to evaluate cerebral hemodynamics was developed using near-infrared spectroscopy (NIRS) with oxygen inhalation. The bilateral fronto-temporal areas of 30 normal volunteers and 33 patients with cerebral ischemia were evaluated with the NIRS system. The subjects inhaled oxygen through a mask for 2?min at a flow rate of 8 L/min. Principal component analysis (PCA) was applied to the data, and a topogram was drawn using the calculated weights. NIRS findings were compared with those of single-photon-emission computed tomography (SPECT). In normal volunteers, no laterality of the PCA weights was observed in 25 of 30 cases (83%). In patients with cerebral ischemia, PCA weights in ischemic regions were lower than in normal regions. In 28 of 33 patients (85%) with cerebral ischemia, NIRS findings agreed with those of SPECT. The results suggest that transmission of the changes in systemic SpO2 were attenuated in ischemic regions. The method discussed here should be clinically useful because it can be used to measure cerebral ischemia easily, repeatedly, and noninvasively.     

A multi-channel near-infrared spectroscopy study of prefrontal cortex activation during working memory task in major depressive disorder

Many neuropsychological studies demonstrate impairment of working memory in patients with major depressive disorder (MDD). However, there are not enough functional neuroimaging studies of MDD patients seeking for the underlying brain activity relevant to working memory function. The objective of this study is to evaluate prefrontal hemodynamic response related to working memory function in patients with MDD. Twenty-four subjects with MDD and 26 age- and gender-matched healthy subjects were recruited for the present study. We measured hemoglobin concentration changes in the prefrontal and superior temporal cortical surface areas during the execution of working memory task (WM; 2-back, letter version) using 52-channel near-infrared spectroscopy (NIRS), which enables real-time monitoring of task-related changes in cerebral blood volumes in the cortical surface areas. MDD patients showed a smaller increase in lateral prefrontal and superior temporal cortex activation during the 2-back task and associated poorer task performance than healthy controls. The results coincided with previous findings in terms of working memory deficits and prefrontal cortex dysfunction in MDD patients, but contradicted with some previous fMRI studies that suggested increased cortical activity during the working memory task in patients with depression. The contradiction may, in part, be explained by a relatively low level of cognitive demand imposed on the subjects in the present study.     

Right frontal activation during the continuous performance test assessed with near-infrared spectroscopy in healthy subjects

Near-infrared spectroscopy (NIRS) is a non-invasive optical technique which has been successfully used to register substantial cerebral ischemia. There are indications that NIRS is sensible enough to detect also small metabolic changes during the performance of cognitive tasks. In the present study, two-channel NIRS of left and right anterior frontal brain areas was applied to investigate brain oxygenation of 10 healthy subjects carrying out the continuous performance test (CPT). Significant differences between the left and right hemisphere were found. These consisted of different changes in deoxyhaemoglobin (HHB), but not in oxyhaemoglobin (O₂HB) in right frontal brain areas compared to baseline during the test. Despite of some methodological restrictions, the findings suggest that the sensitivity of the NIRS-method is sufficient to detect brain oxygenation changes during cognitive activation. Furthermore, the results support the view that execution of the CPT is associated with prevalently right frontal activation.     

Multiple-time replicability of near-infrared spectroscopy recording during prefrontal activation task in healthy men

Near-infrared spectroscopy (NIRS) has the potential for clinical application in neuropsychiatry because it enables non-invasive and convenient measurement of hemodynamic response to cognitive activation. Using 24-channel NIRS in 12 healthy men, we examined the replicability of oxy- and deoxy-hemoglobin concentration ([oxyHb], [deoxyHb]) changes in the prefrontal cortex during the category fluency task over four repeated sessions (each 1-week apart). Multiple methods were employed to evaluate the replicability of magnitude, location, and time course of the NIRS signals ([oxyHb], [deoxyHb]). Task performances did not differ significantly across sessions, nor were they significantly correlated with NIRS signals. Repeated measures ANOVA and variance component analysis indicated high replicability of magnitude for both NIRS measures, whereas the effect sizes of between-session differences in [oxyHb] were not negligible. The number and spatial location of significantly activated channels were sufficiently replicable for both measures, except that the across-session overlap of significantly activated channels was weak in [deoxyHb]. The time course of the activation was acceptably replicable in both measures. Taken together, these findings suggest there is considerable replicability of multiple-time measurements of prefrontal hemodynamics during cognitive activation in men. Further studies using different conditions or assessing sensitivity to longitudinal changes following interventions are necessary.     

Post-disaster depression and vigilance: a functional near-infrared spectroscopy study

The present study was designed to explore the relationships between post-disaster self-reports of depression, vigilance task performance, and frontal cerebral oxygenation. Forty participants (20 women) performed vigilance tasks following a magnitude 7.1 earthquake in Christchurch, New Zealand. In addition to performance, we measured self-reports of depression, anxiety, and stress anchored to the initial earthquake event, and frontal cerebral activity with functional near-infrared spectroscopy. Among the participants, one case may have been an outlier with extremely elevated levels of self-reported depressivity. Excluding the extreme case, there was a correlation between change in response time (response slowing) and depressivity. Including the case there was a correlation between depressivity and right hemisphere oxygenation. These results provide some support for a relationship between moderate depressivity and sustained attention difficulties.     

Cerebrovascular dynamics in patients with migraine: near-infrared spectroscopy study

Migraine is hypothesized to be a neurovascular coupling disorder where the cerebral vascular reactivity is malfunctioning and measuring hemodynamic changes during migraine without causing more disturbance has always been a challenge. Functional near infrared spectroscopy system (fNIRS) is being proposed as an inexpensive, rapid, safe and accurate alternative to fMRI, transcranial doppler sonography (TCD). We have developed NIROXCOPE 201, a novel device for fNIRS which offers 16 source-detector pairs distributed on a probe that is placed on the forehead. Measuring hemodynamic changes during migraine without causing more disturbance has always been a challenge. Using NIROXCOPE 201, we have attempted to investigate the cerebrovascular reactivity of migraine patients to a breath hold task which produces a metabolic perturbation. Six normals and six migraine patients performed four consecutive breath holding task. We calculated the peak and latencies of the initial dip and recovery phases for [Hb], [HbO(2)], [tHb], and [OXY] signals. [Hb], [tHb], and [OXY] ID and R amplitudes of normals are approximately a magnitude higher than migraine patients (P<0.01), while latencies showed no significant differences. Data suggests an altered neurovascular coupling in frontal cortex of migraine patients interictally. The application of NIROXCOPE 201 to patients suffering from other primary headache disorders will reveal diagnostic as well as therapeutic implications of the presented study.     

Enhancing effect of cerebral blood volume by mild exercise in healthy young men: a near-infrared spectroscopy study

A mechanism by which exercise improves brain function may be attributed to increase in cerebral blood volume (CBV) with physical activity. However, the exact exercise intensity that influences CBV is still uncertain. To clarify this issue, 10 healthy young male participants were asked to perform a graded cycling exercise to the point of exhaustion while their prefrontal cortex CBVs are being monitored using near-infrared spectroscopy. Overall responsive cerebral oxygenation showed a non-linear pattern with three distinct phases. The CBV-threshold (CBVT), an event where rapid oxygenation takes place, occurred at approximately 42% of the V O2max. The CBVT preceded the lactate threshold (LT), which was at approximately 55% of the V O2max. The V O2max was not predictive of the CBVT in among the subjects. Our results indicate that oxygenation of the prefrontal cortex increases during graded cycling even at exercise intensities below the LT, suggesting the potential role of mild exercise in enhancing CBV.     

Load-dependent brain activation assessed by time-domain functional near-infrared spectroscopy during a working memory task with graded levels of difficulty

We evaluated frontal brain activation during a mixed attentional/working memory task with graded levels of difficulty in a group of 19 healthy subjects, by means of time-domain functional near-infrared spectroscopy (fNIRS). Brain activation was assessed, and load-related oxy- and deoxy-hemoglobin changes were studied. Generalized linear model (GLM) was applied to the data to explore the metabolic processes occurring during the mental effort and, possibly, their involvement in short-term memorization. GLM was applied to the data twice: for modeling the task as a whole and for specifically investigating brain activation at each cognitive load. This twofold employment of GLM allowed (1) the extraction and isolation of different information from the same signals, obtained through the modeling of different cognitive categories (sustained attention and working memory), and (2) the evaluation of model fitness, by inspection and comparison of residuals (i.e., unmodeled part of the signal) obtained in the two different cases. Results attest to the presence of a persistent attentional-related metabolic activity, superimposed to a task-related mnemonic contribution. Some hemispherical differences have also been highlighted frontally: deoxy-hemoglobin changes manifested a strong right lateralization, whereas modifications in oxy- and total hemoglobin showed a medial localization. The present work successfully explored the capability of fNIRS to detect the two neurophysiological categories under investigation and distinguish their activation patterns.     

Bioengineering assessment of acupuncture, part 5: cerebral near-infrared spectroscopy

The assessment of cortical activation in the brain due to acupuncture is crucial. Thus far functional assessment of cortical responses to certain external stimuli (for examples, manual needle, optical, electrical) are very few due to the lack of suitable techniques to monitor changes of brain activities. Near-infrared spectroscopy has been found to be suitable for functional studies during acupuncture. By this neuromonitoring method, hemodynamic changes coupled to cortical activity can be monitored. Near-infrared spectroscopy is used to measure regional changes in oxyhemoglobin, deoxyhemoglobin, and cytochrome aa3 noninvasively and continuously. The studies in this fifth part of a review article, which have been carried out mainly by the research group of Biomedical Engineering in Anesthesia and Intensive Care Medicine at the Medical University of Graz, demonstrate that near-infrared spectroscopy is a suitable technique for the assessment of cortical changes in response to varying forms of acupuncture. The method is likely to play an important role in providing new insights into the effects of acupuncture on brain function.     

Auditory symptom provocation in dental phobia: a near-infrared spectroscopy study

The act of drilling a tooth belongs to the most feared situations of patients suffering from dental phobia. We presented 25 female patients and 24 nonphobic women with the sound of a dental drill, pleasant and neutral sounds. Brain activation was recorded via near infrared spectroscopy in fronto-parietal and premotor areas. The groups differed in supplementary motor area (SMA) recruitment. Relative to controls, the phobics displayed increased oxy hemoglobin while presented with the phobia-relevant sound, but showed comparable activation in the other conditions. As the SMA is engaged in the preparation of motor actions, the increased response in patients might mirror the priming of flight behavior during exposure. We found no indication of an emotional modulation of parietal and dorsomedial prefrontal cortex activation.