Alteration of hemoglobin oxygenation in the frontal region in elderly depressed patients as measured by near-infrared spectroscopy

A scoping review of functional near-infrared spectroscopy biomarkers in late-life depression: Depressive symptoms, cognitive functioning, and social functioning

Late-life depression is one of the most damaging mental illnesses, disrupting the normal lives of older people by causing chronic illness and cognitive impairment. Patients with late-life depression, accompanied by changes in appetite, insomnia, fatigue and guilt, are more likely to experience irritability, anxiety and somatic symptoms. It increases the risk of suicide and dementia and is a major challenge for the public health systems. The current clinical assessment, identification and effectiveness assessment of late-life depression are primarily based on history taking, mental status examination and scale scoring, which lack subjectivity and precision. Functional near-infrared spectroscopy is a rapidly developing optical imaging technology that objectively reflects the oxygenation of hemoglobin in different cerebral regions during different tasks and assesses the functional status of the cerebral cortex. This article presents a comprehensive review of the assessment of functional near-infrared spectroscopy technology in assessing depressive symptoms, social functioning, and cognitive functioning in patients with late-life depression. The use of functional near-infrared spectroscopy provides greater insight into the neurobiological mechanisms underlying depression and helps to assess these three aspects of functionality in depressed patients. In addition, the study discusses the limitations of previous research and explores potential advances in the field.

NIRS-aided differential diagnosis among patients with major depressive disorder, bipolar disorder, and schizophrenia

BACKGROUND

To establish a clinically applicable neuroimaging-guided diagnostic support system that uses near-infrared spectroscopy (NIRS) for differential diagnosis at the individual level among major depressive disorder (MDD), bipolar disorder (BPD), and schizophrenia (SZ).

METHODS

A total of 192 participants were recruited, including 40 patients with MDD, 38 patients with BPD, 65 patients with SZ, and 49 healthy individuals. We analyzed the spatiotemporal characteristics of hemodynamic responses in the frontotemporal cortex during a verbal fluency test (VFT) measured by NIRS to assess the accuracy of single-subject classification for differential diagnosis among the three psychiatric disorders. The optimal threshold of the frontal centroid value (54 seconds) was utilized on the basis of the findings of the Japanese study.

RESULTS

The application of the optimal threshold of the frontal centroid value (54 seconds) allowed for the accurate differentiation of patients with unipolar MDD (72.5%) from BPD (78.9%) or SZ (84.6%).

CONCLUSION

These results suggest that the NIRS-aided differential diagnosis of major psychiatric disorders can be a promising biomarker in Taiwan. Future multi-site studies are needed to validate our findings.

NPAS4 in the medial prefrontal cortex mediates chronic social defeat stress-induced anhedonia-like behavior and reductions in excitatory synapses

Chronic stress can produce reward system deficits (i.e., anhedonia) and other common symptoms associated with depressive disorders, as well as neural circuit hypofunction in the medial prefrontal cortex (mPFC). However, the molecular mechanisms by which chronic stress promotes depressive-like behavior and hypofrontality remain unclear. We show here that the neuronal activity-regulated transcription factor, NPAS4, in the mPFC is regulated by chronic social defeat stress (CSDS), and it is required in this brain region for CSDS-induced changes in sucrose preference and natural reward motivation in the mice. Interestingly, NPAS4 is not required for CSDS-induced social avoidance or anxiety-like behavior. We also find that mPFC NPAS4 is required for CSDS-induced reductions in pyramidal neuron dendritic spine density, excitatory synaptic transmission, and presynaptic function, revealing a relationship between perturbation in excitatory synaptic transmission and the expression of anhedonia-like behavior in the mice. Finally, analysis of the mice mPFC tissues revealed that NPAS4 regulates the expression of numerous genes linked to glutamatergic synapses and ribosomal function, the expression of upregulated genes in CSDS-susceptible animals, and differentially expressed genes in postmortem human brains of patients with common neuropsychiatric disorders, including depression. Together, our findings position NPAS4 as a key mediator of chronic stress-induced hypofrontal states and anhedonia-like behavior.

Investigating the association between depression and cerebral haemodynamics-A systematic review and meta-analysis

BACKGROUND

Vascular mechanisms may play a role in depression. The aim of this review is to summarise the evidence on alterations in cerebral haemodynamics in depression.

METHODS

MEDLINE (1946- present), Embase (1947-present), Web of Science (1970-present), PsycINFO (1984-present), CINAHL (1976-present) and CENTRAL were searched using a predefined search strategy. A meta-analysis was conducted in four groups: 1) global cerebral blood flow (CBF) in ml/min/100 g, 2) CBF velocity (CBFv) in cm/s (maximum flow of left middle cerebral artery, 3) combined CBF and CBFv, 4) Ratio of uptake of Tc 99 m HMPAO (region of interest compared to whole brain). Data are presented as mean difference or standardised mean difference and 95% confidence interval (95% CI). A narrative synthesis of the remaining studies was performed.

RESULTS

87 studies were included. CBF was significantly reduced in depressed patients compared to HC [15 studies, 538 patients, 416 HC, MD: -2.24 (95% CI -4.12, -0.36), p = 0.02, I² = 64%]. There were no statistically significant differences in other parameters. The narrative synthesis revealed variable changes in CBF in depressed patients, particularly affecting the anterior cingulate and prefrontal cortices.

LIMITATIONS

There were various sources of heterogeneity including the severity of depression, use of antidepressant medication, imaging modality used and reporting of outcomes. All of these factors made direct comparisons between studies difficult.

CONCLUSIONS

The reduction in CBF in depressed patients compared to HCs may indicate a role for assessment and CBF altering interventions in high-risk groups. However, results were inconsistent across studies, warranting further work to investigate specific subgroups.

Prefrontal cortex alterations in major depressive disorder, generalized anxiety disorder and their comorbidity during a verbal fluency task assessed by multi-channel near-infrared spectroscopy

Major depressive disorder (MDD) and generalized anxiety disorder (GAD) are frequently comorbid with each other, and both associated with substantial cognitive impairments; however, it is still unclear whether their impairments are neurobiologically similar or distinct. This study aims to investigate the cognitive functions of the prefrontal cortex (PFC) in patients with MDD and GAD during the verbal fluency task (VFT) using functional near-infrared spectroscopy (fNIRS). Fifty-two patients with MDD, fifty-one patients with GAD, fifty-two patients with the comorbidity of MDD and GAD (CMG), and forty-seven healthy controls (HC) participated in the study. Significant hypoactivation in the left ventrolateral and the left dorsolateral PFC was common in all patient groups when compared to HCs, suggesting a shared etiology. Furthermore,  MDD patients showed significant hypoactivation at the right frontal pole cortex (FPoC) when compared to HCs and significant hypoactivation at the middle FPoC when compared to the CMG patients. Our work is the first fNIRS study to reveal the shared and unique neurobiological profiles of MDD, GAD and their comorbidity under the same standard experimentation condition, suggesting fNIRS holds promise as an adjutant to assist clinical diagnosis.

Impaired Frontal Brain Activity in Patients With Heart Failure Assessed by Near-Infrared Spectroscopy

Background The prevalence of depression and/or anxiety disorders is reported to be higher in patients with heart failure (HF) than in the general population, and patients with HF also have coexisting cognitive problems. Recently, the development of near-infrared spectroscopy (NIRS) has enabled noninvasive measurements of regional cerebral blood volume and brain activity, in terms of cerebral oxyhemoglobin in the cerebral cortex, with a high time resolution. The aim of the current study was to determine the associations between frontal brain activity and depressive symptoms, anxiety status, and cognitive function in patients with HF. Methods and Results We measured and compared frontal brain activity determined by NIRS during a verbal fluency task in patients with HF (n=35) and control subjects (n=28). The Center for Epidemiologic Studies Depression Scale for assessment of depressive symptoms, State-Trait Anxiety Inventory for assessment of anxiety status, Mini-Mental State Examination for assessment of cognitive function, and NIRS were simultaneously conducted. NIRS showed that frontal brain activity was significantly lower in the HF group than in the control subjects (28.5 versus 88.0 mM·mm; P<0.001). Next, we examined the associations between frontal brain activity and the findings of Center for Epidemiologic Studies Depression Scale, State-Trait Anxiety Inventory, Mini-Mental State Examination, and verbal fluency task. There were significant correlations between frontal brain activity and State-Trait Anxiety Inventory (R=-0.228, P=0.046), Mini-Mental State Examination (R=0.414, P=0.017), and verbal fluency task (R=0.338, P=0.007), but not with Center for Epidemiologic Studies Depression Scale (R=-0.160, P=0.233). Conclusions Frontal brain activity assessed by NIRS is reduced and is associated with high anxiety status and low cognitive function in patients with HF.

Diagnostic and Predictive Applications of Functional Near-Infrared Spectroscopy for Major Depressive Disorder: A Systematic Review

INTRODUCTION

Major depressive disorder (MDD) is a global psychiatric disorder with no established biomarker. There is growing evidence that functional near-infrared spectroscopy (fNIRS) has the ability to aid in the diagnosis and prediction of the treatment response of MDD. The aim of this review was to systematically review, and gather the evidence from existing studies that used fNIRS signals in the diagnosis of MDD, correlations with depression symptomatology, and the monitoring of treatment response.

METHODS

PubMed, EMBASE, ScienceDirect, and Cochrane Library databases were searched for published English articles from 1980 to June 2019 that focused on the application of fNIRS for (i) differentiating depressed versus nondepressed individuals, (ii) correlating with depression symptomatology, and in turn (iii) monitoring treatment responses in depression. Studies were included if they utilized fNIRS to evaluate cerebral hemodynamic variations in patients with MDD of any age group. The quality of the evidence was assessed using the Newcastle-Ottawa quality assessment scale.

RESULTS

A total of 64 studies were included in this review, with 12 studies being longitudinal, while the rest were cross-sectional. More than two-thirds of the studies (n = 49) had acceptable quality. fNIRS consistently demonstrated attenuated cerebral hemodynamic changes in depressed compared to healthy individuals. fNIRS signals have also shown promise in correlating with individual symptoms of depression and monitoring various treatment responses.

CONCLUSIONS

This review provides comprehensive updated evidence of the diagnostic and predictive applications of fNIRS in patients with MDD. Future studies involving larger sample sizes, standardized methodology, examination of more brain regions in an integrative approach, and longitudinal follow-ups are needed.

Identification of neurophysiological biotypes in attention deficit hyperactivity disorder

AIM

Findings on neurophysiological alterations in attention deficit hyperactivity disorder (ADHD) have been proposed to underlie ADHD symptoms, with different etiological pathways for different patient biotypes. We aimed at determining whether neurophysiological deviations confirm distinct neurophysiological profiles in ADHD, thus providing direct evidence for the endophenotype concept.

METHODS

Neurophysiological biotypes were investigated in 87 adult patients with ADHD using cluster analysis. Parameters fed into the analysis comprised both hemodynamic and electrophysiological data. To validate results, the independent variables of the clusters were compared with healthy controls.

RESULTS

Cluster analysis yielded three neurophysiologically based ADHD biotypes showing: (i) above-average functioning in attention allocation; (ii) difficulties in attention allocation and inhibitory control but elevated frontal activation during a working memory task; and (iii) functional impairments in state regulation.

CONCLUSION

Classifying patients with ADHD into neurophysiological biotypes sheds light on etiological pathways, with implications for diagnostics and (individualized) treatment options.

STUDIES ON SCHIZOPHRENIA AND DEPRESSIVE DISEASES BASED ON FUNCTIONAL NEAR-INFRARED SPECTROSCOPY

Many investigations have been carried out on functional near infrared spectroscopy (fNIRS) applications in depression and schizophrenia patients that are most mysterious and costliest mental disorders in current society. fNIRS is a new optical method which assesses brain cortex hemodynamic and nervous activities non-invasively and it has been used in medicine as a study tool. Most of the researches of this approach have assessed the homodynamic response of frontal and temporal regions by means of various cognitive tasks. In this research, first, the cognitive task execution techniques have been explained concisely, and then some findings of fNIRS-based researches about depression and schizophrenia have been summarized and assessed. In fNIRS studies that have used various devices with different number of channels, the brain cortex functionality in schizophrenia and depressive patients has been investigated. The results demonstrate that a decrease in prefrontal regions activities can be observed in schizophrenia and depressive patients. Also more detailed studies illustrate ventrolateral, prefrontal and frontopolar region disorders. In severe depressive patients, a decrease in activities of prefrontal and temporal regions has been detected. Therefore, by paying attention to the deficiencies in these regions’ functions, it is possible to treat these diseases.

Evaluation of Brain Activity Using Near-infrared Spectroscopy in Inflammatory Bowel Disease Patients

Depression is implicated as a risk factor for the recurrence of inflammatory bowel disease (IBD). Near-infrared spectroscopy (NIRS) and brain-derived neurotrophic factor (BDNF) are useful tools for evaluation of brain activity and a depressive state, respectively. The aim of this study was to clarify the association between brain activity or depressive symptoms and IBD using NIRS and BDNF. This study included 36 ulcerative colitis (UC) patients, 32 Crohn’s disease (CD) patients, and 17 healthy controls (HC). Center for Epidemiologic Studies Depression Scale (CES-D) scores were determined, NIRS was performed, and serum BDNF levels were measured in all subjects. NIRS showed that the mean oxygenated hemoglobin concentration was significantly lower in the frontal lobe in the UC group than in the HC group (HC 167 ± 106 vs. UC 83.1 ± 85.3, p < 0.05). No significant difference was seen between the HC and CD groups. There were also no significant differences in CED-D scores and BDNF levels among the groups. Changes in the NIRS values of the UC group may indicate decreased brain activity and a fundamental difference between UC and CD, which are often lumped together as two types of IBD.

Disrupted Brain Activation and Deactivation Pattern during Semantic Verbal Fluency Task in Patients with Major Depression

BACKGROUND

Patients with major depressive disorder (MDD) exhibit cognitive impairment, and evidence suggests that the semantic version of the verbal fluency task is a reliable cognitive marker of the disorder. Here, using functional magnetic resonance imaging (fMRI), we investigated the dysfunction of neural processing in acute depression and examined the effects of a 6-week pharmacological intervention.

METHODS

Sixteen patients with MDD participated in 2 fMRI sessions, and 16 healthy control (HC) subjects participated in 1 fMRI session. During each fMRI session, the participants performed a semantic verbal fluency task. Brain activity during the task was compared between groups (MDD 1st fMRI vs. HC) and times (MDD 1st fMRI vs. 2nd fMRI).

RESULTS

Significant brain hypoactivation was observed in MDD patients at the prefrontal, lateral parietal, and limbic regions compared to HC, and MDD patients exhibited hyperactivation at the left precuneus compared to HC. Hypoactivity of the left dorsolateral prefrontal cortex (DLPFC) and hyperactivity of the precuneus were normalized with treatment.

CONCLUSIONS

Hypoactivation of the left DLPFC and hyperactivation of the precuneus should be considered as dysregulation of anticorrelated brain networks during a cognitive demanding task. This failure of network regulation may be an important factor in the pathophysiology of MDD.

Sleep complaints are associated with reduced left prefrontal activation during a verbal fluency task in patients with major depression: A multi-channel near-infrared spectroscopy study

BACKGROUND

Recent studies have indicated the potential clinical use of near-infrared spectroscopy (NIRS) as a tool for assisting in the diagnosis of major depressive disorder (MDD). Although sleep complaints are often manifested in MDD, no study has elucidated the possible association between the objective evaluation of sleep and NIRS signals in MDD.

METHODS

Fourteen patients with MDD and 15 healthy controls wore waist actigraphy equipment before the NIRS scan to investigate sleep parameters. We performed a 52-channel NIRS scan and measured changes in oxygenated hemoglobin ([oxy-Hb]) during a verbal fluency task.

RESULTS

In patients with MDD, a significant negative correlation was observed between the 17-item Hamilton Depressive Rating Scale score and cerebral reactivity of the right temporal region (p_s:=-0.804 to -0.762; FDR-corrected; p=0.008-0.012). The Pittsburgh Sleep Questionnaire Index, which enables assessment of continuous sleep quality and disturbances, was negatively correlated with [oxy-Hb] changes in the left prefrontal cortex (p_s=-0.630 to -0.551; FDR-corrected; p=0.043-0.048). Actigraphic sleep variables prior to the NIRS measurement showed no significant correlation with [oxy-Hb] changes.

LIMITATIONS

The limitations were small sample size with the low severity of depression and the use of actigraphy for only one night.

CONCLUSION

Self-rated sleep disturbance were associated with decreased left prefrontal reactivity during a verbal fluency task in patients with MDD. Our result indicates that the reactivity of the prefrontal region is susceptible to sleep complaints, providing further evidence to support potential clinical application of NIRS.

Differences in the Pulsatile Component of the Skin Hemodynamic Response to Verbal Fluency Tasks in the Forehead and the Fingertip

Several studies have claimed that hemodynamic signals measured by near-infrared spectroscopy (NIRS) on the forehead exhibit different patterns during a verbal fluency task (VFT) in various psychiatric disorders, whereas many studies have noted that NIRS signals can reflect task-related changes in skin blood flow. If such a task-related skin hemodynamic response is also observed in the fingertip, a simpler biomarker may be developed. Furthermore, determining the difference in the response pattern may provide physiological insights into the condition. We found that the magnitude of the pulsatile component in skin hemodynamic signals increased on the forehead (p < 0.001 for N = 50, p = 0.073 for N = 8) but decreased on the fingertip (p < 0.001, N = 8) during the VFT, whereas the rate in both areas increased (p < 0.02, N = 8). We also did not find a repetition effect in both the rate and the magnitude on the fingertip, whereas the effect was present in the magnitude (p < 0.02, N = 8) but not in the rate on the forehead. These results suggest that the skin vasomotor system in the forehead could have a different vessel mechanism to psychological tasks compared to the fingertip.

Study protocol for the randomised controlled trial: Ketamine augmentation of ECT to improve outcomes in depression (Ketamine-ECT study)

BACKGROUND

There is a robust empirical evidence base supporting the acute efficacy of electroconvulsive therapy (ECT) for severe and treatment resistant depression. However, a major limitation, probably contributing to its declining use, is that ECT is associated with impairment in cognition, notably in anterograde and retrograde memory and executive function. Preclinical and preliminary human data suggests that ketamine, used either as the sole anaesthetic agent or in addition to other anaesthetics, may reduce or prevent cognitive impairment following ECT. A putative hypothesis is that ketamine, through antagonising glutamate receptors, protects from excess excitatory neurotransmitter stimulation during ECT. The primary aim of the ketamine-ECT study is to investigate whether adjunctive ketamine can attenuate the cognitive impairment caused by ECT. Its secondary aim is to examine if ketamine increases the speed of clinical improvement with ECT.

METHODS/DESIGN

The ketamine ECT study is a multi-site randomised, placebo-controlled, double blind trial. It was originally planned to recruit 160 moderately to severely depressed patients who had been clinically prescribed ECT. This recruitment target was subsequently revised to 100 patients due to recruitment difficulties. Patients will be randomly allocated on a 1:1 basis to receive either adjunctive ketamine or saline in addition to standard anaesthesia for ECT. The primary neuropsychological outcome measure is anterograde verbal memory (Hopkins Verbal Learning Test-Revised delayed recall task) after 4 ECT treatments. Secondary cognitive outcomes include verbal fluency, autobiographical memory, visuospatial memory and digit span. Efficacy is assessed using observer and self-report efficacy measures of depressive symptomatology. The effects of ECT and ketamine on cortical activity during cognitive tasks will be studied in a sub-sample using functional near-infrared spectroscopy (fNIRS).

DISCUSSION

The ketamine-ECT study aims to establish whether or not adjunctive ketamine used together with standard anaesthesia for ECT will significantly reduce the adverse cognitive effects observed after ECT. Potential efficacy benefits of increased speed of symptom improvement and a reduction in the number of ECT treatments required will also be assessed, as will safety and tolerability of adjunctive ketamine. This study will provide important evidence as to whether adjunctive ketamine is routinely indicated for ECT given for depression in routine NHS clinical practice.

TRIAL REGISTRATION

Current Controlled Trials: ISRCTN14689382 (assigned 30/07/2012); EudraCT Number: 2011-005476-41.

Brain correlates of verbal fluency in subthreshold psychosis assessed by functional near-infrared spectroscopy

The prevalence of subthreshold psychotic symptoms in the general population has gained increasing interest as a possible precursor of psychotic disorders. The goal of the present study was to evaluate whether neurobiological features of subthreshold psychotic symptoms can be detected using verbal fluency tasks and functional near-infrared spectroscopy (fNIRS). A large data set was obtained from the Zurich Program for Sustainable Development of Mental Health Services (ZInEP). Based on the SCL-90-R subscales 'Paranoid Ideation' and 'Psychoticism' a total sample of 188 subjects was assigned to four groups with different levels of subthreshold psychotic symptoms. All subjects completed a phonemic and semantic verbal fluency task while fNIRS was recorded over the prefrontal and temporal cortices. Results revealed larger hemodynamic (oxy-hemoglobin) responses to the phonemic and semantic conditions compared to the control condition over prefrontal and temporal cortices. Subjects with high subthreshold psychotic symptoms exhibited significantly reduced hemodynamic responses in both conditions compared to the control group. Further, connectivity between prefrontal and temporal cortices revealed significantly weaker patterns in subjects with high subthreshold psychotic symptoms compared to the control group, possibly indicating less incisive network connections associated with subthreshold psychotic symptoms. The present findings provide evidence that subthreshold forms of psychotic symptoms are associated with reduced hemodynamic responses and connectivity in prefrontal and temporal cortices during verbal fluency that can be identified using fNIRS.

Individual classification of ADHD children by right prefrontal hemodynamic responses during a go/no-go task as assessed by fNIRS

While a growing body of neurocognitive research has explored the neural substrates associated with attention deficit hyperactive disorder (ADHD), an objective biomarker for diagnosis has not been established. The advent of functional near-infrared spectroscopy (fNIRS), which is a noninvasive and unrestrictive method of functional neuroimaging, raised the possibility of introducing functional neuroimaging diagnosis in young ADHD children. Previously, our fNIRS-based measurements successfully visualized the hypoactivation pattern in the right prefrontal cortex during a go/no-go task in ADHD children compared with typically developing control children at a group level. The current study aimed to explore a method of individual differentiation between ADHD and typically developing control children using multichannel fNIRS, emphasizing how spatial distribution and amplitude of hemodynamic response are associated with inhibition-related right prefrontal dysfunction. Thirty ADHD and thirty typically developing control children underwent a go/no-go task, and their cortical hemodynamics were assessed using fNIRS. We explored specific regions of interest (ROIs) and cut-off amplitudes for cortical activation to distinguish ADHD children from control children. The ROI located on the border of inferior and middle frontal gyri yielded the most accurate discrimination. Furthermore, we adapted well-formed formulae for the constituent channels of the optimized ROI, leading to improved classification accuracy with an area under the curve value of 85% and with 90% sensitivity. Thus, the right prefrontal hypoactivation assessed by fNIRS would serve as a potentially effective biomarker for classifying ADHD children at the individual level.

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Objective neuro-functional biomarker to diagnose ADHD has not been established.

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We measured right prefrontal fNIRS signals with a go/no-go task execution executed.

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We assessed the accuracy of classification between ADHD and healthy control.

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We found the way of classification with 90% sensitivity of diagnostic prediction.

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Our results would provide screening tool clinically applicable for ADHD children.

Prefrontal activation predicts social functioning improvement after initial treatment in late-onset depression

The activation of oxygenated hemoglobin (oxy-Hb) has been shown to be lacking in the prefrontal cortex (PFC) of patients with late-onset depression (LOD), in verbal fluency task (VFT)-related near-infrared spectroscopy (NIRS). In our previous studies, we have emphasized the connection between the lack of activation in the frontopolar cortex and social functioning disorder in patients with LOD. In this study, we investigated whether the responsiveness to medical treatment of untreated patients with LOD, particularly social functioning improvements, could be predicted by NIRS findings at the initial examination. The subjects were 29 patients with LOD who were diagnosed with major depression at 65 years or older at the initial examination (mean age ± standard deviation, 72.4 ± 5.71 years). We measured the changes in hemoglobin concentration in the prefrontal and temporal cortex regions during a VFT by using 52-channel NIRS. In addition, depression status and social functioning were evaluated with the Hamilton Depression Rating Scale and the Social Adaptation Self-evaluation Scale, respectively, at the initial examination and 8 weeks after the treatment. A negative correlation was found between the NIRS activation in the right ventrolateral PFC region before treatment and the improvement in social functioning. These results suggested that the social functioning improvements were greater in LOD with initially lower NIRS activation in the right ventrolateral PFC region. NIRS is a simple technique that can be used before treatment to evaluate the social functioning levels of patients with LOD, and predict social functioning improvement after treatment.

Near-infrared spectroscopy for examination of prefrontal activation during cognitive tasks in patients with major depressive disorder: a meta-analysis of observational studies

AIMS

Near-infrared spectroscopy has the potential for aiding the diagnosis of major depressive disorder. The purpose of this study was to systematically review the evidence from observational studies regarding the use of near-infrared spectroscopy in patients with major depressive disorder and to identify the characteristic pattern of prefrontal lobe activity in major depressive disorder.

METHODS

medline, PubMed, Cochrane Library and Web of Science databases were searched in December 2013. All case-control studies were included. The quality of evidence was examined using the Newcastle-Ottawa Quality Assessment Scale. The primary outcome measures were the mean oxygenated and deoxygenated hemoglobin alterations of the cerebral cortex during cognitive activation periods. The standard mean difference for the overall pooled effects across the included studies was estimated using random or fixed effect models. The primary outcome measures were included in the meta-analysis.

RESULTS

Fourteen studies met the inclusion criteria. Six studies (n = 692 participants) were included in the analysis of the mean oxygenated hemoglobin alterations; the pooled mean standardized difference was -0.74 (95% confidence interval, -0.97 to -0.52), indicating that patients with major depressive disorder were associated with attenuated increase in oxygenated hemoglobin during cognitive activation in the prefrontal regions compared to healthy controls. Five studies (n = 668 participants) were included in the analysis of mean deoxygenated-hemoglobin changes; the pooled standardized mean difference was 0.18 (95% confidence interval, -0.20 to 0.56).

CONCLUSIONS

Using near-infrared spectroscopy measurements, we observed that compared to healthy subjects, patients with major depressive disorder had significantly lower prefrontal activation during cognitive tasks.

Effects of 2 weeks of low-intensity cycle training with different pedaling rates on the work rate at lactate threshold

PURPOSE

This study examined (1) the effects of a single bout of exercise at different pedaling rates on physiological responses, pedal force, and muscle oxygenation, and (2) the effects of 2 weeks of training with different pedaling rates on work rate at lactate threshold (WorkLT).

METHODS

Sixteen healthy men participated in the study. An incremental exercise test involving pedaling a cycling ergometer at 50 rpm was conducted to assess maximal oxygen consumption and WorkLT. The participants performed constant workload, submaximal exercise tests at WorkLT intensity with three different pedaling rates (35, 50, and 75 rpm). Oxygen consumption ([Formula: see text]O2), blood pressure, heart rate (HR), blood lactate, and pedal force were measured and oxy-hemoglobin/myoglobin concentration (OxyHb/Mb) at vastus lateralis was monitored by near-infrared spectroscopy during exercise. The participants were then randomly assigned to cycling exercise training at WorkLT in either the low or high frequency pedaling rate (LFTr, 35 rpm or HFTr, 75 rpm) group. Each 60-min training session was performed five times/week.

RESULTS

Despite maintaining the same work rate, [Formula: see text]O2 and HR were significantly lower at 35 than 75 rpm. Conversely, integrated pedal force was significantly higher at 35 than 75 rpm. Peripheral OxyHb/Mb was significantly lower at 35 than 75 rpm. After 2 weeks of training, WorkLT normalized to body mass significantly increased in the LFTr, but not the HFTr group.

CONCLUSIONS

Pedaling rate and the corresponding pedal force and peripheral oxygenation during cycling exercise influence the effect of training at LT on WorkLT.

Acute neuropharmacological effects of atomoxetine on inhibitory control in ADHD children: a fNIRS study

The object of the current study is to explore the neural substrate for effects of atomoxetine (ATX) on inhibitory control in school-aged children with attention deficit hyperactivity disorder (ADHD) using functional near-infrared spectroscopy (fNIRS). We monitored the oxy-hemoglobin signal changes of sixteen ADHD children (6–14 years old) performing a go/no-go task before and 1.5 h after ATX or placebo administration, in a randomized, double-blind, placebo-controlled, crossover design. Sixteen age- and gender-matched normal controls without ATX administration were also monitored. In the control subjects, the go/no-go task recruited the right inferior and middle prefrontal gyri (IFG/MFG), and this activation was absent in pre-medicated ADHD children. The reduction of right IFG/MFG activation was acutely normalized after ATX administration but not placebo administration in ADHD children. These results are reminiscent of the neuropharmacological effects of methylphenidate to up-regulate reduced right IFG/MFG function in ADHD children during inhibitory tasks. As with methylphenidate, activation in the IFG/MFG could serve as an objective neuro-functional biomarker to indicate the effects of ATX on inhibitory control in ADHD children. This promising technique will enhance early clinical diagnosis and treatment of ADHD in children, especially in those with a hyperactivity/impulsivity phenotype.

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We assessed the effects of atomoxetine administration to ADHD children using fNIRS.

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Normal healthy control subjects recruited the right IFG/MFG during go/no-go tasks.

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Pre-medicated ADHD children exhibited reduced right IFG/MFG activation.

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The activation was acutely normalized by atomoxetine, but not by placebo.

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The right IFG/MFG activation may serve as an objective neuro-functional biomarker.

Comparison of alterations in cerebral hemoglobin oxygenation in late life depression and Alzheimer's disease as assessed by near-infrared spectroscopy

Background

Patients with Alzheimer’s disease (AD) often present with apathy symptoms resembling the decreased motivation observed in depressed patients. Therefore, differentiating the initial phase of AD from late life depression may be difficult in some cases. Near-infrared spectroscopy (NIRS) is a functional neuroimaging modality that uses near-infrared light to measure changes in hemoglobin concentration on the cortical surface during activation tasks. The objective of this study was to investigate differences in brain activation associated with late life depression and with AD by means of NIRS.

Methods

NIRS was performed in 30 patients with depression, 28 patients with AD, and 33 healthy controls, all aged 60 years or older. During two tasks, a verbal fluency task and a visuospatial task, changes in oxygenated hemoglobin concentration in the frontal and parietal cortices were investigated.

Results

In the visuospatial task, cortical activation was lower in the depressed group than in the AD group, and significant differences were observed in the parietal cortex.

Conclusions

NIRS can detect differences in brain activation between patients with late life depression and those with AD. NIRS is a promising tool for the differential diagnosis of late life depression and AD.

Motor response investigation in individuals with cerebral palsy using near infrared spectroscopy: pilot study

Cerebral palsy (CP) describes a group of motor impairment syndromes secondary to genetic that may be due to acquired disorders of the developing brain. In this study, near infrared spectroscopy (NIRS) is used to investigate the prefrontal cortical activation and lateralization in response to the planning and execution of motor skills in controls and individuals with CP. The prefrontal cortex, which plays a dominant role in the planning and execution of motor skill stimulus, is noninvasively imaged using a continuous wave-based NIRS system. During the study, 7 controls (4 right-handed and 3 left-handed) and 2 individuals with CP (1 right-handed and 1 left-handed) over 18 years of age performed 30 s of a ball throwing task followed by 30 s rest in a 5-block paradigm. The optical signal acquired from the NIRS system was processed to elucidate the activation and lateralization in the prefrontal region of controls and individuals with CP. The preliminary result indicated a difference in activation between the task and rest conditions in all the participant types. Bilateral dominance was observed in the prefrontal cortex of controls in response to planning and execution of motor skill tasks, while an ipsilateral dominance was observed in individuals with CP. In conjunction, similar contralateral dominance was observed during rest periods, both in controls and individuals with CP.

Language-specific cortical activation patterns for verbal fluency tasks in Japanese as assessed by multichannel functional near-infrared spectroscopy

In Japan, verbal fluency tasks are commonly utilized as a standard paradigm for neuropsychological testing of cognitive and linguistic abilities. The Japanese "letter fluency task" is a mora/letter fluency task based on the phonological and orthographical characteristics of the Japanese language. Whether there are similar activation patterns across languages or a Japanese-specific mora/letter fluency pattern is not certain. We investigated the neural correlates of overt mora/letter and category fluency tasks in healthy Japanese. The category fluency task activated the bilateral fronto-temporal language-related regions with left-superior lateralization, while the mora/letter fluency task led to wider activation including the inferior parietal regions (left and right supramarginal gyrus). Specific bilateral supramarginal activation during the mora/letter fluency task in Japanese was distinct from that of similar letter fluency tasks in syllable-alphabet-based languages: this might be due to the requirement of additional phonological processing and working memory, or due to increased cognitive load in general.

Right prefrontal activation as a neuro-functional biomarker for monitoring acute effects of methylphenidate in ADHD children: An fNIRS study

An objective biomarker is a compelling need for the early diagnosis of attention deficit hyperactivity disorder (ADHD), as well as for the monitoring of pharmacological treatment effectiveness. The advent of fNIRS, which is relatively robust to the body movements of ADHD children, raised the possibility of introducing functional neuroimaging diagnosis in younger ADHD children. Using fNIRS, we monitored the oxy-hemoglobin signal changes of 16 ADHD children (6 to 13 years old) performing a go/no-go task before and 1.5 h after MPH or placebo administration, in a randomized, double-blind, placebo-controlled, crossover design. 16 age- and gender-matched normal controls without MPH administration were also monitored. Relative to control subjects, unmedicated ADHD children exhibited reduced activation in the right inferior frontal gyrus (IFG) and middle frontal gyrus (MFG) during go/no-go tasks. The reduced right IFG/MFG activation was acutely normalized after MPH administration, but not after placebo administration. The MPH-induced right IFG/MFG activation was significantly larger than the placebo-induced activation. Post-scan exclusion rate was 0% among 16 right-handed ADHD children with IQ > 70. We revealed that the right IFG/MFG activation could serve as a neuro-functional biomarker for monitoring the acute effects of methylphenidate in ADHD children. fNIRS-based examinations were applicable to ADHD children as young as 6 years old, and thus would contribute to early clinical diagnosis and treatment of ADHD children.

Evaluation of cerebral activity in the prefrontal cortex in mood [affective] disorders during animal-assisted therapy (AAT) by near-infrared spectroscopy (NIRS): a pilot study

OBJECTIVE

Previous studies have shown the possibility that animal-assisted therapy (AAT) is useful for promoting the recovery of a patient's psychological, social, and physiological aspect. As a pilot study, we measured the effect that AAT had on cerebral activity using near-infrared spectroscopy (NIRS), and examined whether or not NIRS be used to evaluate the effect of AAT biologically and objectively.

METHODS

Two patients with mood [affective] disorders and a healthy subject participated in this study. We performed two AAT and the verbal fluency task (VFT).

RESULTS

The NIRS signal during AAT showed great [oxy-Hb] increases in most of the prefrontal cortex (PFC) in the two patients. When the NIRS pattern during AAT was compared with that during VFT, greater or lesser differences were observed between them in all subjects.

CONCLUSION

The present study suggested that AAT possibly causes biological and physiological changes in the PFC, and that AAT is useful for inducing the activity of the PFC in patients with depression who have generally been said to exhibit low cerebral activity in the PFC. In addition, the possibility was also suggested that the effect of AAT can be evaluated using NIRS physiologically and objectively.

A brief review on the history of human functional near-infrared spectroscopy (fNIRS) development and fields of application

This review is aimed at celebrating the upcoming 20th anniversary of the birth of human functional near-infrared spectroscopy (fNIRS). After the discovery in 1992 that the functional activation of the human cerebral cortex (due to oxygenation and hemodynamic changes) can be explored by NIRS, human functional brain mapping research has gained a new dimension. fNIRS or optical topography, or near-infrared imaging or diffuse optical imaging is used mainly to detect simultaneous changes in optical properties of the human cortex from multiple measurement sites and displays the results in the form of a map or image over a specific area. In order to place current fNIRS research in its proper context, this paper presents a brief historical overview of the events that have shaped the present status of fNIRS. In particular, technological progresses of fNIRS are highlighted (i.e., from single-site to multi-site functional cortical measurements (images)), introduction of the commercial multi-channel systems, recent commercial wireless instrumentation and more advanced prototypes.

Predictability of investment behavior from brain information measured by functional near-infrared spectroscopy: a bayesian neural network model

In line with previous studies using fMRI and as is apparent from experimental results, cerebral blood flow (oxygenated hemoglobin (oxyHb) concentration) in the medial prefrontal cortex (MPFC) and orbital cortex (OFC) as is observed with fNIRS (functional near-infrared spectroscopy) is presumed to be closely related to reward prediction and risk prediction as part of decision-making under risk. Results of analysis using a predictive model with a three-layer perceptron revealed that changes in the oxyHb concentration in cerebral blood as indicated by fNIRS observation include information to effectively predict investment behavior. This paper indicates that adding oxyHb concentration at the aforementioned sites in the brain as a predictive factor allows prediction of subjects' investment behavior with a considerable degree of precision. This fact indicates that information provided by fNIRS allows valid analysis of investment behavior and it also suggests a wide-ranging practical applicability for this information like investment assistance using fNIRS.

HomER: a review of time-series analysis methods for near-infrared spectroscopy of the brain

Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging tool for studying evoked hemodynamic changes within the brain. By this technique, changes in the optical absorption of light are recorded over time and are used to estimate the functionally evoked changes in cerebral oxyhemoglobin and deoxyhemoglobin concentrations that result from local cerebral vascular and oxygen metabolic effects during brain activity. Over the past three decades this technology has continued to grow, and today NIRS studies have found many niche applications in the fields of psychology, physiology, and cerebral pathology. The growing popularity of this technique is in part associated with a lower cost and increased portability of NIRS equipment when compared with other imaging modalities, such as functional magnetic resonance imaging and positron emission tomography. With this increasing number of applications, new techniques for the processing, analysis, and interpretation of NIRS data are continually being developed. We review some of the time-series and functional analysis techniques that are currently used in NIRS studies, we describe the practical implementation of various signal processing techniques for removing physiological, instrumental, and motion-artifact noise from optical data, and we discuss the unique aspects of NIRS analysis in comparison with other brain imaging modalities. These methods are described within the context of the MATLAB-based graphical user interface program, HomER, which we have developed and distributed to facilitate the processing of optical functional brain data.

Effect of probe arrangement on reproducibility of images by near-infrared topography evaluated by a virtual head phantom

The effect of the probe arrangement on the reproducibility of topographic images of the concentration changes in oxygenated hemoglobin and deoxygenated hemoglobin is evaluated by a virtual head phantom. A virtual head phantom consists of five types of tissue the 3D structure of which is based on a magnetic resonance imaging scan of an adult head. Localized and broadened brain activation is assumed in a virtual head phantom. The topographic images are obtained from the reflectance detected by the standard probe arrangement and the double-density probe arrangement. The uneven thickness of the superficial layer, which cannot be evaluated by the previous slab model, affects the distribution of measured activation in the topographic image, and this reduces the position reproducibility of near-infrared (NIR) topography with the standard probe arrangement. The overlapping measurements by the double-density probe arrangement can improve the reproducibility of the image obtained by NIR topography.

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.

Frontal lobe function in bipolar disorder: A multichannel near-infrared spectroscopy study

Frontal lobe dysfunction has been implicated as one of the pathophysiological bases of bipolar disorder. Detailed time courses of brain activation in the bipolar disorder group were investigated using multichannel near-infrared spectroscopy (NIRS), a recently developed functional neuroimaging technology with a high time resolution, and were compared with those in the major depression and healthy control groups. Seventeen patients with bipolar disorder, 11 equally depressed patients with major depression, and 17 healthy controls participated in the study. Changes in oxy hemoglobin concentration ([oxy-Hb]) during cognitive and motor tasks were monitored using frontal and temporal probes of two sets of 24-channel NIRS machines. [oxy-Hb] increases in the bipolar disorder group were smaller than those in the healthy control group during the early period of a verbal fluency task, larger than those in the major depression and healthy control groups during the late period of this task, and were smaller than those in the major depression group during a finger-tapping task. Depressive symptoms and antidepressant dosages did not correlate with [oxy-Hb] changes in the two patient groups. Bipolar disorder and major depression were characterized by preserved but delayed and reduced frontal lobe activations, respectively, in the present high-time-resolution study by multichannel NIRS.

Dynamic physiological modeling for functional diffuse optical tomography

Diffuse optical tomography (DOT) is a noninvasive imaging technology that is sensitive to local concentration changes in oxy- and deoxyhemoglobin. When applied to functional neuroimaging, DOT measures hemodynamics in the scalp and brain that reflect competing metabolic demands and cardiovascular dynamics. The diffuse nature of near-infrared photon migration in tissue and the multitude of physiological systems that affect hemodynamics motivate the use of anatomical and physiological models to improve estimates of the functional hemodynamic response. In this paper, we present a linear state-space model for DOT analysis that models the physiological fluctuations present in the data with either static or dynamic estimation. We demonstrate the approach by using auxiliary measurements of blood pressure variability and heart rate variability as inputs to model the background physiology in DOT data. We evaluate the improvements accorded by modeling this physiology on ten human subjects with simulated functional hemodynamic responses added to the baseline physiology. Adding physiological modeling with a static estimator significantly improved estimates of the simulated functional response, and further significant improvements were achieved with a dynamic Kalman filter estimator (paired t tests, n=10, P<0.05). These results suggest that physiological modeling can improve DOT analysis. The further improvement with the Kalman filter encourages continued research into dynamic linear modeling of the physiology present in DOT. Cardiovascular dynamics also affect the blood-oxygen-dependent (BOLD) signal in functional magnetic resonance imaging (fMRI). This state-space approach to DOT analysis could be extended to BOLD fMRI analysis, multimodal studies and real-time analysis.

Hypofrontality and microvascular dysregulation in remitted late-onset depression assessed by functional near-infrared spectroscopy

Accumulated evidence suggests the involvement of vascular factors in late-onset depression. Late-onset depression has characteristics of poor outcome, cognitive decline, and high prevalence rather than early-onset depression. The aim of the present study was to determine whether or not the functional hypofrontality--that is, hypoperfusion and hypometabolism in the frontal lobes-seen in late-onset depression is a trait-dependent abnormality of microvascular regulation. This study was conducted on 10 patients with remitted late-onset major depressive disorder (MDD) and 10 healthy volunteers matched for vascular factors and subcortical, or white matter, hyperintensities (WMH). Using near-infrared spectroscopy combined with magnetic resonance imaging, we investigated the microvascular reactivity in the prefrontal cortex during a cognitive task and during carbon dioxide (CO(2)) inhalation. Activation of the prefrontal cortex during the cognitive task was significantly less in patients as compared with controls, although task performance was not significantly different between the two groups. In the patients, a tendency of negative correlation between the reduced prefrontal activation during a cognitive task and the severity of hyperintensity in periventricular region was observed. Vasomotor reactivity to CO(2) inhalation was significantly lower in the patients than in the controls. Although there was no significant association between the activation during the cognitive and that during the CO(2) inhalation task, the present results suggest that prefrontal microvascular dysregulation as shown by NIRS is involved in the pathophysiological basis of functional hypofrontality in late-onset depression. This finding will provide a new framework for the development of diagnostic methods, treatments, and preventive strategies against late-onset depression.

Optical Topography with Near-Infrared Spectroscopy During a Verbal-Fluency Task

Abstract: In this study we investigated the changes in brain oxygenation in 22 subjects during a verbal fluency task (VFT) using multichannel near-infrared spectroscopy (NIRS). To assess topographical effects in more detail we measured over bilateral prefrontal and over the left frontolateral cortex in 11 subjects. We found significantly higher increases in O2HB, as a sign of cerebral activation, during the VFT compared to a verbal repetition control task over the left prefrontal and the inferior left lateral brain areas. These results underscore the value of NIRS to assess functional brain activation during cognitive tasks. Furthermore, it shows the advantage of multichannel compared to previously used single channel NIRS measurements.

Bilateral prefrontal cortex oxygenation responses to a verbal fluency task: a multichannel time-resolved near-infrared topography study

The letter-fluency task-induced response over the prefrontal cortex is investigated bilaterally on eight subjects using a recently developed compact, eight-channel, time-resolved, near-IR system. The cross-subject mean values of prefrontal cortex oxygen saturation (SO2) were 68.8+/-3.2% (right) and 71.0+/-3.6% (left), and of total hemoglobin concentration (tHb) were 69.6+/-9.6 microM (right) and 69.5+/-9.9 microM (left). The typical cortical activation response to the cognitive task [characterized by an increase in oxyhemoglobin (O2Hb) with a concurrent decrease in deoxyhemoglobin (HHb)] at each measurement point is observed in only four subjects. In this subset, the amplitude of the O2Hb increase and HHb decrease is uniform over each prefrontal cortex area and comparable between the two hemispheres. These findings agree with previous studies using continuous wave functional near-IR spectroscopy and functional magnetic resonance imaging, therefore demonstrating the potential of a time-resolved spectroscopy approach. In addition, a significant increase in SO2 levels was observed in the right (1.1+/-0.5%) compared to left side of the prefrontal cortex (0.9+/-0.5%) (P=0.005). A different pattern of cortical activation (characterized by the lack of HHb decrease or even increased HHb) was observed in the remaining subjects.

Sex and age dependencies of cerebral blood volume changes during cognitive activation: a multichannel near-infrared spectroscopy study

In this study, we measured the change in cerebral hemoglobin concentrations during a cognitive task using multichannel near-infrared spectroscopy (NIRS), and investigated the relationship between regional cerebral blood volume and sex, age, and task performance. Thirty-nine healthy volunteers (24 males and 15 females; mean age, 33.0 years) participated after giving their informed consent and performed a word fluency task. The relative oxy-hemoglobin concentration ([oxy-Hb]) was measured using frontal and temporal probes with two sets of 24-channel NIRS machines. The effects of sex, age, and task performance on [oxy-Hb] changes were analyzed using analysis of covariance: with sex, age, and task performance as independent variables, and [oxy-Hb] changes as dependent variables, and years of education as covariates. The effects on [oxy-Hb] increase were significant in many channels in the frontal and temporal probes for sex, that is the most prominent effect, and in a few frontal channels for age: [oxy-Hb] increases were larger in males than in females, and in the young than in the middle-aged. The effects on [oxy-Hb] increase were not significant for task performance, but [oxy-Hb] increases in subjects with low performance tended to be larger than those in subjects with high performance. The results demonstrated that multichannel NIRS could detect cerebral activation during cognitive tasks and clarify sex- and age-dependent differences in such cerebral activation. Sex- and age-dependent differences in cerebral activation, as demonstrated in the present study, should be considered when interpreting cerebral blood volume, cerebral blood flow, and cerebral glucose metabolism data.

Multichannel near-infrared spectroscopy in depression and schizophrenia: cognitive brain activation study

BACKGROUND

Recent developments in near-infrared spectroscopy (NIRS) have enabled the noninvasive clarification of brain functions in psychiatric disorders with measurement of hemoglobin concentrations as cerebral blood volume.

METHODS

Ten patients with depression, 13 patients with schizophrenia, and 16 age- and gender-matched healthy control subjects participated in the study after giving consent. The relative concentrations of oxyhemoglobin [oxyHb] were measured with frontal and temporal probes every.1 sec during word fluency and unilateral finger tapping tasks, with two 24-channel NIRS machines.

RESULTS

The [oxyHb] increase patterns during the word fluency task varied among the three groups, although their task performances were similar: the depression group was characterized by a smaller [oxyHb] increase during the first half of the task period and the schizophrenic group by a small trough of [oxyHb] at the start of the task period and [oxyHb] re-increase in the posttask period. [OxyHb] increases during the finger-tapping task were rather larger in the patient groups than in the control group.

CONCLUSIONS

The characteristic time courses of [oxyHb] changes in the frontal lobe were elucidated for depression and schizophrenia. Near-infrared spectroscopy, with its noninvasiveness and high time resolution, can be a useful tool for research and clinical purposes in psychiatry.

Near-infrared spectroscopy analysis of frontal lobe dysfunction in schizophrenia

BACKGROUND

Previous studies have shown that near-infrared spectroscopy (NIRS) has high temporal resolution, requires little restraint, and is suitable for examining the effect of psychological tasks on brain circulation. In the present study, frontal function in schizophrenic patients was analyzed by NIRS during random number generation (RNG), ruler-catching (RC), and sequential finger-to-thumb (SFT) tasks.

METHODS

Two sets of NIRS probes were attached to the foreheads of 13 schizophrenic patients and 10 control subjects approximately at Fp1-F7 and Fp2-F8. Near-infrared spectroscopy was conducted at a sampling rate of 1 Hz, with the pathlength being determined by time-resolved spectroscopy with differential pathlength factor measurements. The absolute changes in oxygenated (oxy-Hb) and deoxygenated (deoxy-Hb) hemoglobin concentrations in response to each task were measured, and total hemoglobin (total-Hb) concentration was calculated as the sum of the two.

RESULTS

During RNG task, total- and oxy-Hb concentrations increased, and deoxy-Hb decreased, but the responses were significantly smaller in schizophrenic patients. During RC task, oxy-Hb in schizophrenic patients tended to decrease, in contrast to the mostly increasing response in control subjects. No group difference was observed during SFT task.

CONCLUSIONS

Task-dependent profile of functional abnormalities was observed in schizophrenic frontal brain metabolism. These results support the usefulness of NIRS data in investigating frontal lobe dysfunction and evaluating psychopathologic condition in schizophrenic patients.

Hypoactivation of the prefrontal cortex during verbal fluency test in PTSD: a near-infrared spectroscopy study

Several studies have suggested that there is frontal dysfunction in subjects with posttraumatic stress disorder (PTSD). We investigated the relationship between alterations of the hemodynamic response of the prefrontal cortex during a cognitive task (verbal fluency task; VFT) and memory function measured using the Wechsler Memory Scale-Revised (WMS-R). The subjects were victims of the Tokyo Subway Sarin attack with (n = 8) or without (n = 26) PTSD. Hemodynamic response in the prefrontal cortex was measured using a 24-channel near-infrared spectroscopy (NIRS) system. Subjects with PTSD had a significantly smaller response of oxygenated hemoglobin and total hemoglobin during the VFT compared with those without PTSD, although there was no significant difference in performance on the VFT. Subjects with PTSD had significantly lower scores on attention and concentration in the WMS-R, which was positively correlated with the increase of total hemoglobin during the VFT. The 'frontal dysfunction' observed in subjects with PTSD may be a secondary phenomenon to reduced attentional capacity.

Non-invasive neuroimaging using near-infrared light

This article reviews diffuse optical brain imaging, a technique that employs near-infrared light to non-invasively probe the brain for changes in parameters relating to brain function. We describe the general methodology, including types of measurements and instrumentation (including the tradeoffs inherent in the various instrument components), and the basic theory required to interpret the recorded data. A brief review of diffuse optical applications is included, with an emphasis on research that has been done with psychiatric populations. Finally, we discuss some practical issues and limitations that are relevant when conducting diffuse optical experiments. We find that, while diffuse optics can provide substantial advantages to the psychiatric researcher relative to the alternative brain imaging methods, the method remains substantially underutilized in this field.