A near-infrared spectroscopy study of prefrontal cortex activation during a verbal fluency task and carbon dioxide inhalation in individuals with bipolar disorder

Deep neural network to differentiate brain activity between patients with euthymic bipolar disorders and healthy controls during verbal fluency performance: A multichannel near-infrared spectroscopy study

In this study, we aimed to differentiate between euthymic bipolar disorder (BD) patients and healthy controls (HC) based on frontal activity measured by fNIRS that were converted to spectrograms with Convolutional Neural Networks (CNN). And also, we investigated brain regions that cause this distinction. In total, 29 BD patients and 28 HCs were recruited. Their brain cortical activities were measured using fNIRS while performing letter versions of VFT. Each one of the 24 fNIRS channels was converted to a 2D spectrogram on which a CNN architecture was designed and utilized for classification. We found that our CNN algorithm using fNIRS activity during a VFT is able to differentiate subjects with BD from healthy controls with 90% accuracy, 80% sensitivity, and 100% specificity. Moreover, validation performance reached an AUC of 94%. From our individual channel analyses, we observed channels corresponding to the left inferior frontal gyrus (left-IFC), medial frontal cortex (MFC), right dorsolateral prefrontal cortex (DLPFC), Broca area, and right premotor have considerable activity variation to distinguish patients from HC. fNIRS activity during VFT can be used as a potential marker to classify euthymic BD patients from HCs. Activity particularly in the MFC, left-IFC, Broca's area, and DLPFC have a considerable variation to distinguish patients from healthy controls.

A scoping review of near infrared spectroscopy studies employing a verbal fluency task in bipolar disorder

BACKGROUND

Deficits in cognitive functioning, including attention, memory, and executive functions, along with impairments in language production, are present in patients with bipolar disorder (BD) patients during mood phases, but also during euthymia.Verbal fluency tasks (VFTs), being able to evaluate integrity of a wide range of cognitive domains and represent, can be used to screen for these disturbances. Neuroimaging studies, including Near-InfraRed Spectroscopy (NIRS), have repeatedly showed widespread alterations in the prefrontal and temporal cortex during the performance of VFTs in BD patients. This review aims to summarize the results of NIRS studies that evaluated hemodynamic responses associated with the VFTs in prefrontal and temporal regions in BD patients.

METHODS

We performed a scoping review of studies evaluating VFT-induced activation in prefrontal and temporal regions in BD patients, and the relationship between NIRS data and various clinical variables.

RESULTS

15 studies met the inclusion criteria. In BD patients, compared to healthy controls, NIRS studies showed hypoactivation of the dorsolateral prefrontal cortex, ventrolateral prefrontal cortex and anterior temporal regions. Moreover, clinical variables, such as depressive and social adaptation scores, were negatively correlated with hemodynamic responses in prefrontal and temporal regions, while a positive correlation were reported for measures of manic symptoms and impulsivity.

LIMITATIONS

The heterogeneity of the studies in terms of methodology, study design and clinical characteristics of the samples limited the comparability of the findings.

CONCLUSIONS

Given its non-invasiveness, good time-resolution and no need of posturalconstraint, NIRS technique could represent a useful tool for the evaluation of prefrontal and temporal haemodynamic correlates of cognitive performances in BD patients.

Functional near-infrared spectroscopy during the verbal fluency task of English-Speaking adults with mood disorders: A preliminary study

Functional near-infrared spectroscopy (fNIRS) provides a direct and objective assessment of cerebral cortex function. It may be used to determine neurophysiological differences between psychiatric disorders with overlapping symptoms, such as major depressive disorder (MDD) and bipolar disorder (BD). Therefore, this preliminary study aimed to compare fNIRS signals during the verbal fluency task (VFT) of English-speaking healthy controls (HC), patients with MDD and patients with BD. Fifteen HCs, 15 patients with MDD and 15 patients with BD were recruited. Groups were matched for age, gender, ethnicity and education. Relative oxy-haemoglobin and deoxy-haemoglobin changes in the frontotemporal cortex was monitored with a 52-channel fNIRS system. Integral values of the frontal and temporal regions were derived as a measure cortical haemodynamic response magnitude. Both patient groups had lower frontal and temporal region integral values than HCs, and patients with MDD had lower frontal region integral value than patients with BD. Moreover, patients could be differentiated from HCs using the frontal and temporal integral values, and patient groups could be differentiated using the frontal region integral values. VFT performance, clinical history and symptom severity were not associated with integral values. These results suggest that prefrontal cortex haemodynamic dysfunction occurs in mood disorders, and it is more extensive in MDD than BD. The fNIRS-VFT paradigm may be a potential tool for differentiating MDD from BD in clinical settings, and these findings need to be verified in a larger sample of English-speaking patients with mood disorders.

Brain activation during verbal fluency task in type II bipolar disorder patients: a near-infrared spectroscopy study

BACKGROUND

Previous studies have shown that BD patients exhibited impairment when performing a verbal fluency task (VFT) and abnormal prefrontal cortex activation during this task. However, no study has specifically examined whether patients with type II BD demonstrate difficulty in performing VFT and impairments in relevant neural correlates or whether these are related to psychotic symptoms, the present study aimed to examine these issues.

METHODS

Forty-nine patients with type II BD (21 patients with psychotic symptoms [BDIIp] and 28 patients without psychotic symptoms [BDIIn]) and 45 matched healthy controls (HCs) participated the study and completed the VFTs, while their brain activity was recorded with near-infrared spectroscopy (NIRS).

RESULTS

Both BDIIp and BDIIn patients showed poorer performance on VFTs than HCs. In addition, BDII patients showed lower brain activation than HCs in bilateral dorsolateral prefrontal cortex and right frontal pole, these results were mainly driven by BDIIn patients. Moreover, subjective psychotic symptoms were positively significantly correlated with left dorsolateral prefrontal cortex activation in BDII patients.

CONCLUSIONS

Type II BD patients showed significant impairment when performing VFTs and reduced activation in the prefrontal cortex, and subjective psychotic symptoms were associated with brain activation in left dorsolateral prefrontal cortex in BDII patients.

The characteristic of cognitive impairments in patients with bipolar II depression and its association with N-acetyl aspartate of the prefrontal white matter

Background

Cognitive deficit is acknowledged as a core feature of clinical manifestations of bipolar disorder (BD). However, the underlying mechanism of cognitive impairment in bipolar II depression has remained uncertain. We aim to determine the association of cognitive impairments with biochemical metabolism using proton magnetic resonance spectroscopy (¹H-MRS) and a battery of neuropsychological testing.

Methods

The current study was designed to assess four cognitive domains in a sample of 110 patients with bipolar II depression and 110 healthy controls, using a battery of 6 cognitive tests, including the Digit Symbol Substitution Test (DSST), Wisconsin Cart Sorting Test (WCST), Trail Making Test Part B (TMT-B), Digit Span Test (DST), TMT-part A (TMT-A) and Verbal Fluency Test (VFT). Metabolite levels were obtained in the following brain regions of interest: bilateral prefrontal white matter (PWM), bilateral anterior cingulate cortex (ACC), bilateral lenticular nucleus (LN), and bilateral thalamus. N-acetyl aspartate (NAA)/creatine (Cr) and choline-containing compounds (Cho)/Cr ratios are analyzed.

Results

Patients with bipolar II depression performed significantly worse on DSST (score), TMT (completion time), DSB (score), and VFT (valid word number) when compared with healthy controls. In the bilateral PWM, NAA/Cr ratios in the PWM were significantly reduced (bilaterally) than those in healthy controls. Correlation analysis was conducted with data from patients with bipolar II depression, we found that the NAA/Cr ratio of the left PWM was positively correlated with the score of DS and DSB, and the NAA/Cr ratio of the right PWM was negatively correlated with the completion time of TMT-B.

Conclusions

Our findings suggested that psychomotor speed, executive function, working memory, and verbal fluency are impaired in patients with BD II depression. Hypoactivity NAA/Cr in bilateral PWM may be associated with BD II depression's pathophysiology and results in cognitive dysfunction.

Distinct patterns of blood oxygenation in the prefrontal cortex in clinical phenotypes of schizophrenia and bipolar disorder

BACKGROUND

Schizophrenia (SZ) and bipolar disorder (BD) are characterized by different clinical symptoms, and have previously been considered as categorically separate. However, several lines of evidence controversially suggest that these two disorders may run on a continuum. While it is therefore important to evaluate the subtle differences between SZ and BD, few studies have investigated the difference of brain functioning between the two by focusing on the common symptoms of cognitive functioning and impulsivity, rather than positive/negative and mood symptoms. Recent developments in near-infrared spectroscopy (NIRS) technology have enabled noninvasive assessment of brain function in people with psychiatric disorders.

METHODS

Near-infrared spectroscopy (NIRS) using 24-channels was conducted during the verbal fluency task (VFT) and Stroop color-word task (SCWT) in 38 patients diagnosed with SZ, 34 patients with BD, and 26 age- and sex-matched healthy controls.

RESULTS

Oxyhemoglobin changes in the prefrontal cortex (PFC) were significantly lower particularly in the SZ compared to control group during the VFT. On the other hand, these were significantly lower particularly in the BD and SZ group to control group during the SCWT. Regression analysis showed that hemodynamic changes were significantly correlated with verbal memory and impulsivity in both disorders.

CONCLUSION

These findings suggest that different hemodynamic responses in the prefrontal cortex might reflect cognitive functioning and impulsivity, providing a greater insight into SZ and BD pathophysiology.

Prefrontal activation during a working memory task differs between patients with unipolar and bipolar depression: A preliminary exploratory study

BACKGROUND

To identify bipolar disorder during the initial stages of a depressive episode has always been a great clinical challenge. Patterns of functional brain activity may underlie the differences in the neural mechanisms of bipolar depression (BD) and unipolar depression (UD). This study aimed to investigate the differences in neural activity between BD and UD patients during executive task.

METHODS

We performed a 52-channel near-infrared spectroscopy (NIRS) scan in 39 patients with BD, 35 patients with UD, and 36 healthy controls (HCs). The relative concentration changes in oxygenated hemoglobin ([oxy-Hb]) and deoxygenated hemoglobin ([deoxy-Hb]) during a 1-back working memory task were measured for each channel. Clinical characteristics including current mood were evaluated within one week prior to NIRS examination.

RESULTS

Compared to HCs, BD (CH34: Z = -2.354, P = 0.019) and UD patients (CH18: Z = -2.358, P = 0.018; CH30: Z = -2.174, P = 0.030; CH34: Z = -1.990, P = 0.047) showed reduced activation of [oxy-Hb] in the inferior prefrontal region. Compared to patients with UD, patients with BD showed less decreased [oxy-Hb] changes in the left frontopolar cortex (FPC) (CH18: Z = -2.366, P = 0.018), left pars opercularis and pars triangularis (POPE/PTRI) regions (Broca's area) (CH30: Z = -2.333, P = 0.020). No correlation existed between clinical characteristics and NIRS measurements.

LIMITATIONS

The effect of medication could not be excluded, and behavioral data was not systematically collected.

CONCLUSION

The results from this preliminary exploratory study suggest distinct prefrontal activation patterns underlie BD and UD, especially in the left frontopolar region and Broca's area. The NIRS-based prefrontal activation measurement may serve as a potential marker to aid in differentiating bipolar from unipolar depression.

Reduced Prefrontal Activation During the Tower of London and Verbal Fluency Task in Patients With Bipolar Depression: A Multi-Channel NIRS Study

Background: The Tower of London (TOL) task is one of the most commonly used tests for evaluating executive functions, and can indicate planning and problem-solving abilities. The aim of this study was to evaluate hemodynamic changes between the task period and rest period in patients with bipolar depression during the TOL task and the verbal fluency task (VFT) using near-infrared spectroscopy (NIRS). Methods: Forty-three patients with bipolar depression and 32 healthy controls (HCs) matched for sex, age, handedness, and years of education were enrolled in this study. All participants were aged between 16 and 50. All patients in our study were taking medications such as antidepressants, antipsychotics and mood stabilizers at the time of measurement. Changes in oxygenated hemoglobin (oxy-Hb) levels in frontal areas during the TOL task and VFT were evaluated using a 41-channel NIRS system. Results: During the TOL task, the patients with bipolar depression exhibited significantly smaller changes in the bilateral dorsal-lateral prefrontal cortex (DLPFC) than the HCs. During the VFT task, the patients with bipolar depression exhibited significantly smaller changes in the right ventrolateral prefrontal cortex (VLPFC), the right DLPFC and both the right and left prefrontal cortex (PFC) than the HCs. Limitations: Our sample size was small, and the effects of medication cannot be excluded. Conclusions: These results indicate that planning and problem solving dysfunction is related to the impairment of the prefrontal cortex in patients with bipolar depression, and NIRS can be used to assess planning and problem solving abilities, which are essential to daily life in patients with bipolar disorder.

Functional near infra-red spectroscopy (fNIRS) in schizophrenia: A review

The research on the alterations in functional connectivity in schizophrenia has been facilitated by development of an array of functional neuroimaging techniques. Functional Near Infra Red Spectroscopy (fNIRS) is a novel diffuse optical neuromonitring method with its own advantages and limitations. The advantages of fNIRS have made it to be frequently used as a research tool by medical community in different settings. In fNIRS the property of haemoglobin to absorb near infrared light is used to measure brain activity. It provides the indirect measurement of the neuronal activity in the areas of interest. The advantage of fNIRS being less restrictive has made it to be used more commonly in the research of psychiatric disorders in general, schizophrenia in particular. The fNIRS studies on patients with schizophrenia have shown haemodynamic hypo activation primarily in the prefrontal cortex during various cognitive tasks. In this review, initially we have briefly explained the basic principles of fNIRS followed by detailed review of fNIRS findings in patients with schizophrenia.

Prefrontal oxygenation during verbal fluency and cognitive function in adolescents with bipolar disorder type II

Evaluation of depressive states in children can be challenging. Most of the studies that have investigated cognitive function and cerebral blood volume changes using functional MRI (fMRI) in bipolar disorder (BD) have been confined to BDI or heterogeneous cohorts with attention-deficit/hyperactivity disorder (ADHD). This study investigated cognitive functions in adolescents with BDII and without ADHD using near-infrared spectroscopy (NIRS) and a Das-Naglieri Cognitive Assessment System (DN-CAS). Ten patients with BDII and without ADHD symptoms and 10 age- and gender-matched healthy controls were enrolled in the present study. NIRS was used to detect hemoglobin concentration changes during a verbal fluency test (VFT). In addition, the DN-CAS was used to evaluate cognitive function in four domains: planning, attention, simultaneous, and successive processing. Significant differences between the BDII and control groups in [oxy-Hb] changes during the early phase of VFT were observed in the lower prefrontal cortex but not in cognitive functioning. Furthermore, there was a significant correlation between planning and attention scores in BD subjects.

Verbal fluency in bipolar disorders: A systematic review and meta-analysis

BACKGROUND

One of the main features of bipolar disorder (BD), besides mood dysregulation, is an alteration of the structure of language. Bipolar patients present changes in semantic contents, impaired verbal associations, abnormal prosody and abnormal speed of language highlighted with various experimental tasks. Verbal fluency tasks are widely used to assess the abilities of bipolar patients to retrieve and produce verbal material from the lexico-semantic memory. Studies using these tasks have however yielded discrepant results. The aim of this study was thus to determine the extent of the verbal fluency impairment in BD patients and to evaluate if the deficits are affected by the type of task or by mood states.

METHODS

A systematic literature search was conducted in MEDLINE, EBSCOHost and Google Scholar and relevant data were submitted to a meta-analysis.

RESULTS

Thirty-nine studies were retained providing data for 52 independent groups of BD patients. The overall meta-analysis revealed a moderate verbal fluency impairment in BD compared to healthy controls (effect size d=0.61). Comparisons between mood states showed significant differences only between euthymic and manic patients and only on category fluency performances.

LIMITATIONS

This review is limited by the heterogeneity between studies for the characteristics of BD populations. Also, few of the retained studies examined depressive or mixed episodes.

CONCLUSIONS

This work confirms that BD patients present with moderate verbal fluency impairments, and underlines the specific effect of mood state on category fluency. This emphasizes the need to distinguish semantic from phonological processes in verbal fluency assessments in BD.

Reduced prefrontal activation during performance of the Iowa Gambling Task in patients with bipolar disorder

The Iowa Gambling Task (IGT) is a complex decision-making task in which monetary wins and losses guide the development of strategies. The objective of this study was to evaluate hemodynamic responses of patients with bipolar disorder (BD) during performance of the IGT using near-infrared spectroscopy (NIRS). Participants comprised 13 patients and 15 healthy control subjects who were matched for age, sex, handedness, and intelligence quotient. Relative changes in oxygenated and deoxygenated hemoglobin (oxy-Hb and deoxy-Hb) levels in the frontal region were measured using a 46-channel NIRS system. All subjects were evaluated using NIRS during a verbal fluency task (VFT) and the IGT. During performance of the IGT, BD patients showed significantly decreased oxy-Hb levels in the bilateral orbitofrontal cortex (OFC) and left prefrontal cortex (PFC) compared with normal control subjects. However, during the VFT, patients with BD showed no significant changes in oxy-Hb levels compared with control subjects. Changes in oxy-Hb levels in the bilateral OFC and the PFC during the IGT were negatively correlated with total scores on the Hamilton Rating Scale for Depression (HAM-D). Although the IGT was useful for differentiating patients with BP from control subjects, no significant differences in autonomic activity were observed.

Association between longitudinal changes in prefrontal hemodynamic responses and social adaptation in patients with bipolar disorder and major depressive disorder

BACKGROUND

Patients with affective disorders exhibit changes in regional brain function and show abnormal social adaptation. However, to our knowledge, no near-infrared spectroscopy (NIRS) study has examined the relationship between these two phenomena longitudinally. This study examined the region-specific functional abnormality associated with bipolar disorder (BD) and major depressive disorder (MDD), and the association between particular longitudinal changes in regional activation and social adaptation.

METHODS

We evaluated frontotemporal functioning during a verbal fluency test (VFT) for patients with BD (N=18), those with MDD (N=10), and healthy controls (HCs; N=14) using NIRS. NIRS measurements and the Social Adaptation Self-evaluation Scale (SASS) were administered twice with an interval of approximately 6 months.

RESULTS

The BD and MDD groups showed lesser activation than the HCs in the bilateral ventro-lateral prefrontal cortex and the anterior part of the temporal cortex (VLPFC/aTC). Longitudinal changes in SASS scores were positively associated with the extent of change in left VLPFC/aTC activation in the BD group and with right VLPFC/aTC activation in the MDD group.

LIMITATIONS

Our small sample size limited statistical power, and the effect of medication and multiple comparisons cannot be excluded, although these effects were considered in the interpretation of the present results.

CONCLUSION

Longitudinal increases of VLPFC/aTC activation were associated with improvement in social adaptation in patients with BD and those with MDD. NIRS measurement could be a useful tool for objective evaluation of changes in social adaptation in BD and MDD.

Blunted brain activation in patients with schizophrenia in response to emotional cognitive inhibition: a functional near-infrared spectroscopy study

INTRODUCTION

Patients with schizophrenia (SZ) have deficits of facial emotion processing and cognitive inhibition, but the brain pathophysiology underlying these deficits and their interaction are not clearly understood. We tested brain activity during an emotional face go/no-go task that requires rapid executive control affected by emotional stimuli in patients with SZ using functional near-infrared spectroscopy (fNIRS).

METHODS

Twenty-five patients with SZ and 28 healthy control subjects were studied. We evaluated behavioral performance and used fNIRS to measure oxygenated hemoglobin concentration changes in fronto-temporal areas during the emotional go/no-go task with emotional and non-emotional blocks.

RESULTS

Patients with SZ made more errors and had longer reaction times in both test blocks compared with healthy subjects. Significantly greater activation in the inferior, superior, middle, and orbital frontal regions were observed in healthy subjects during the emotional go/no-go block compared to the non-emotional go/no-go block, but this difference was not observed in patients with SZ. Relative to healthy subjects, patients with SZ showed less activation in the superior and orbital frontal and middle temporal regions during the emotional go/no-go block.

DISCUSSION

Our results suggest that fronto-temporal dysfunction in patients with SZ is due to an interaction between abnormal processing of emotional facial expressions with negative valence and cognitive inhibition, especially during the rapid selection of rule-based associations that override automatic emotional response tendencies. They indicate that fronto-temporal dysfunction is involved in the pathophysiology of emotional-cognitive deficits in patients with SZ.

Dorsolateral prefrontal hemodynamic responses during a verbal fluency task in hypomanic bipolar disorder

OBJECTIVES

Neuroimaging studies have suggested prefrontal dysfunction in response to cognitive activation in bipolar disorder (BD). However, its characteristics in manic states have not been well understood. Thus, we compared prefrontal hemodynamic responses during a cognitive task between hypomanic and depressive states in BD. We then longitudinally compared hypomanic and subsequent euthymic states.

METHODS

The prefrontal function of 27 patients with BD (11 hypomanic and 16 depressed) and 12 age- and gender-matched healthy controls (HCs) was evaluated using near-infrared spectroscopy (NIRS) during a verbal fluency task (VFT). Hypomanic symptoms were assessed using the Young Mania Rating Scale. Among the 11 hypomanic patients, eight participated in the second NIRS measurement after their hypomanic symptoms resolved.

RESULTS

VFT performance did not differ among hypomanic, depressed, and HC groups. Both BD groups exhibited significantly lower activation during the VFT than HCs in the broader bilateral prefrontal cortex. Hemodynamic changes in the left dorsolateral prefrontal cortex (DLPFC) in the hypomanic patients with BD were significantly larger than those in the depressed patients. In addition, hypomanic symptom severity was positively correlated with activation in the left DLPFC and frontopolar cortex in patients with BD. Follow-up measurement of the hypomanic patients revealed that prefrontal activation was decreased after hypomanic symptoms resolved.

CONCLUSIONS

Combining cross-sectional and longitudinal assessments, the present results suggest that prefrontal hemodynamic responses associated with cognitive activation differ between hypomanic and depressive states in BD. NIRS measurement could be a useful tool for objectively evaluating state-dependent characteristics of prefrontal hemodynamics in BD.

Left temporal activation associated with depression severity during a verbal fluency task in patients with bipolar disorder: a multichannel near-infrared spectroscopy study

BACKGROUND

Neuroimaging studies using multichannel near-infrared spectroscopy (NIRS) have provided compelling evidence about the dysfunction of the frontotemporal cortices in patients with bipolar disorder (BD). However, it remains unclear whether the dysfunction is associated with mood state or symptom severity. Using NIRS, we aimed to clarify differences in oxygenated hemoglobin (oxy-Hb) activation between depressive and euthymic states as well as regional brain dysfunction in relation to symptom severity in BD.

METHODS

Fifty-five patients with BD, including 30 with bipolar depression (BPD) and 25 with euthymic bipolar disorder (BPE), and 28 healthy controls (HCs) participated in the study. Regional hemodynamic changes during a verbal fluency task (VFT) were monitored using a 52-channel NIRS apparatus.

RESULTS

The mean oxy-Hb changes induced by VFT were significantly smaller in the BD patients than in the HCs in 18 channels in the frontotemporal regions (false-discovery rate p<0.05, p=0.000-0.011). The BPD group exhibited significantly smaller changes in mean oxy-Hb compared with the BPE group in three channels of the left temporal region (p=0.005-0.014). In the BD patients, significant negative correlations were observed between mean oxy-Hb changes in the left temporal regions and the severity of depression.

LIMITATIONS

Our sample size was small, making the results susceptible to type II errors.

CONCLUSIONS

BD patients have persistent hypofunction of the frontotemporal cortical regions. Moreover, the hemodynamic response in the left temporal regions is associated with symptom severity.

The use of the Clock Drawing Test in bipolar disorder with or without dementia of Alzheimer’s type

There is limited data regarding the cognitive profile from screening tests of older adults with bipolar disorder (BD) with dementia. Objective To investigate the Clock Drawing Test (CDT) among older adults with BD with and without Alzheimer’s disease (AD). Method 209 older adults (79 with BD without dementia and 70 controls; 60 with AD, being 27 with BD) were included to evaluate the performance of three CDT scoring scales, beyond the Mini-Mental State Examination (MMSE) and verbal fluency (VFT). Results Patients with BD without dementia presented with lower scores in MMSE, VF and one CDT scoring scale than controls. Patients with BD and AD presented with lower scores in VF and CDT scoring scales than patients with only AD. All CDT scales presented similar sensitivity and specificity for BD and non-BD groups. Conclusion Elderly subjects with BD showed greater impairment in CDT in both groups of normal cognition and AD.

Cognitive impairment in euthymic older adults with bipolar disorder: a controlled study using cognitive screening tests

BACKGROUND/OBJECTIVE

Cognitive impairment is a common feature of bipolar disorder (BD), with increased risk of developing dementia in late life. The aim of this study was to investigate the performance on cognitive screening tests in a sample of older adults with BD, as compared to non-BD subjects.

METHODS

186 older adults (86 with BD and 100 without BD) were included. Patients were stratified according to cognitive performance (normal cognition, mild impairment, and dementia). The comparison group comprised healthy controls; subjects with cognitive impairment but no dementia (CIND); or patients with probable or possible Alzheimer disease (AD). Sixty-five subjects were cognitively unimpaired (35 BD), 65 had CIND (25 BD), and 56 AD (26 BD). In each of these levels of cognitive function, we compared the performance of BD and non-BD subjects on the Mini-Mental State Examination (MMSE), verbal fluency test (VFT), and the Clock Drawing Test (CDT).

RESULTS

Non-demented patients with BD had a slightly worse global cognitive performance as compared with healthy controls and patients with CIND, as shown by lower scores on the MMSE. Similarly, BD patients performed worse on the VFT, both in the normal cognition range and in the dementia range. Finally, demented BD patients had a significantly worse performance on the CDT as compared with patients with dementia due to AD.

CONCLUSION

Older adults with BD perform significantly worse on some cognitive screening tests as compared with those without BD across different levels of cognition.

Single event-related changes in cerebral oxygenated hemoglobin using word game in schizophrenia

Neuroimaging studies have been conducted using word generation tasks and have shown greater hypofrontality in patients with schizophrenia compared with healthy subjects. In this study, we compared the characteristics of oxygenated hemoglobin changes involved in both phonological and categorical verbal fluency between 35 outpatients with schizophrenia and 35 healthy subjects during a Japanese "shiritori" task using single-event-related near-infrared spectroscopy. During this task, the schizophrenic patients showed significantly smaller activation in the prefrontal cortex area than the controls. In addition, a significant positive correlation was obtained between oxygenated hemoglobin changes (prefrontal cortex area, inferior parietal area) and the severity of positive psychiatric symptoms. It is possible that hypofrontality of patients may be a diagnostic assistance tool for schizophrenia, and that the relationship between activation and positive syndrome scores may be of help in predicting functional outcome in patients.

Relationship between prefrontal function during a cognitive task and social functioning in male Japanese workers: a multi-channel near-infrared spectroscopy study

To investigate whether prefrontal function during a cognitive task reflects the social functioning of male Japanese workers, prefrontal function during a working memory task in 181 male workers was measured by multi-channel near-infrared spectroscopy (NIRS). Social functioning was assessed using the Social Adaptation Self-Evaluation Scale (SASS). The results indicated that cortical oxygenation level increases in dorsolateral prefrontal region showed significant positive correlations with the interest and motivation factor scores on the SASS. These results suggest that dorsolateral prefrontal function is associated with the interest and motivation factor in social functioning in male workers and that NIRS could be an addition to the medical tools for monitoring these characteristics on mental health examination.

Functional near-infrared spectroscopy for the assessment of speech related tasks

Over the past years functional near-infrared spectroscopy (fNIRS) has substantially contributed to the understanding of language and its neural correlates. In contrast to other imaging techniques, fNIRS is well suited to study language function in healthy and psychiatric populations due to its cheap and easy application in a quiet and natural measurement setting. Its relative insensitivity for motion artifacts allows the use of overt speech tasks and the investigation of verbal conversation. The present review focuses on the numerous contributions of fNIRS to the field of language, its development, and related psychiatric disorders but also on its limitations and chances for the future.

Pathophysiological interference with neurovascular coupling - when imaging based on hemoglobin might go blind

Assessing neuronal activity by non-invasive functional brain imaging techniques which are based on the hemodynamic response depends totally on the physiological cascade of metabolism and blood flow. At present, functional brain imaging with near infrared spectroscopy (NIRS) or BOLD-fMRI is widely used in cognitive neuroscience in healthy subjects where neurovascular coupling and cerebrovascular reactivity can be assumed to be intact. Local activation studies as well as studies investigating functional connectivity between brain regions of the resting brain provide a rapidly increasing body of knowledge on brain function in humans and animals. Furthermore, functional NIRS and MRI techniques are increasingly being used in patients with severe brain diseases and this use might gain more and more importance for establishing their use in the clinical routine. However, more and more experimental evidence shows that changes in baseline physiological parameters, pharmacological interventions, or disease-related vascular changes may significantly alter the normal response of blood flow and blood oxygenation and thus may lead to misinterpretation of neuronal activity. In this article we present examples of recent experimental findings on pathophysiological changes of neurovascular coupling parameters in animals and discuss their potential implications for functional imaging based on hemodynamic signals such as fNIRS or BOLD-fMRI. To enable correct interpretation of neuronal activity by vascular signals, future research needs to deepen our understanding of the basic mechanisms of neurovascular coupling and the specific characteristics of disturbed neurovascular coupling in the diseased brain.