Increased cerebral blood flow associated with better response inhibition in bipolar disorder

Prefrontal photobiomodulation produces beneficial mitochondrial and oxygenation effects in older adults with bipolar disorder

There is growing evidence of mitochondrial dysfunction and prefrontal cortex (PFC) hypometabolism in bipolar disorder (BD). Older adults with BD exhibit greater decline in PFC-related neurocognitive functions than is expected for age-matched controls, and clinical interventions intended for mood stabilization are not targeted to prevent or ameliorate mitochondrial deficits and neurocognitive decline in this population. Transcranial infrared laser stimulation (TILS) is a non-invasive form of photobiomodulation, in which photons delivered to the PFC photo-oxidize the mitochondrial respiratory enzyme, cytochrome-c-oxidase (CCO), a major intracellular photon acceptor in photobiomodulation. TILS at 1064-nm can significantly upregulate oxidized CCO concentrations to promote differential levels of oxygenated vs. deoxygenated hemoglobin (HbD), an index of cerebral oxygenation. The objective of this controlled study was to use non-invasive broadband near-infrared spectroscopy to assess if TILS to bilateral PFC (Brodmann area 10) produces beneficial effects on mitochondrial oxidative energy metabolism (oxidized CCO) and cerebral oxygenation (HbD) in older (≥50 years old) euthymic adults with BD (N = 15). As compared to sham, TILS to the PFC in adults with BD increased oxidized CCO both during and after TILS, and increased HbD concentrations after TILS. By significantly increasing oxidized CCO and HbD concentrations above sham levels, TILS has the potential ability to stabilize mitochondrial oxidative energy production and prevent oxidative damage in the PFC of adults with BD. In conclusion, TILS was both safe and effective in enhancing metabolic function and subsequent hemodynamic responses in the PFC, which might help alleviate the accelerated neurocognitive decline and dysfunctional mitochondria present in BD.

Neurovascular alterations in bipolar disorder: A review of perfusion weighted magnetic resonance imaging studies

BACKGROUND

Bipolar Disorder (BD) is a severe chronic psychiatric disorder whose aetiology is still largely unknown. However, increasing literature reported the involvement of neurovascular factors in the pathophysiology of BD, suggesting that a measure of Cerebral Blood Flow (CBF) could be an important biomarker of the illness. Therefore, since, to date, Magnetic Resonance Perfusion Weighted Imaging (PWI) techniques, such as Dynamic Susceptibility Contrast (DSC) and Arterial Spin Labelling (ASL), are the most common approaches that allow non-invasive in-vivo perfusion measurements,this review aims to summarize the results from all PWI studies that evaluated the CBF in BD.

METHODS

A bibliographic search in PubMed up until May 2021 was performed. 16 PWI studies that used DSC or ASL sequences met our inclusion criteria.

RESULTS

Overall, the results supported the presence of hyper-perfusion in the cingulate cortex and fronto-temporal regions, as well as the presence of hypo-perfusion in the cerebellum in BD, compared with both healthy controls and patients with unipolar depression. CBF changes after cognitive and aerobic training, as well as in relation with other physiological, clinical, and neurocognitive variables were also reported.

LIMITATIONS

The heterogeneity across the studies, in terms of experimental designs, sample selection, and methodological approach employed, limited the studies' comparison.

CONCLUSIONS

These findings showed CBF alterations in the cingulate cortex, fronto-temporal regions, and cerebellum in BD, suggesting that CBF may be an important pathophysiological marker of BD that merits further investigation to clarify the extent of neurovascular alterations.

Shared and specific characteristics of regional cerebral blood flow and functional connectivity in unmedicated bipolar and major depressive disorders

BACKGROUND

Identifying brain similarities and differences between bipolar disorder (BD) and major depressive disorder (MDD) can help us better understand their pathophysiological mechanisms and develop more effective treatments. However, the features of whole-brain regional cerebral blood flow (CBF) and intrinsic functional connectivity (FC) underlying BD and MDD have not been directly compared.

METHODS

Eighty-eight unmedicated BD II depression patients, 95 unmedicated MDD patients, and 96 healthy controls (HCs) underwent three-dimensional arterial spin labeling (3D ASL) and resting-state functional MRI (rs-fMRI). The functional properties of whole brain CBF and seed-based resting-state FC further performed based on those regions with changed CBF were analyzed between the three groups.

RESULTS

The patients with BD and MDD showed commonly increased CBF in the left posterior lobe of the cerebellum and the left middle temporal gyrus (MTG) compared with HCs. The CBF of the left MTG was positively associated with 24-items Hamilton Depression Rating Scale scores in MDD patients. Decreased FC between the left posterior lobe of the cerebellum and the left inferior frontal gyrus (IFG) was observed only in patients with BD compared with HCs.

CONCLUSION

Patients with BD and those with MDD shared common features of CBF in the posterior lobe of the cerebellum and the MTG. The altered posterior lobe of the cerebellum-IFG FC can be considered as a potential biomarker for the differentiation of patients with BD from those with MDD.

Transcranial Infrared Laser Stimulation Improves Cognition in Older Bipolar Patients: Proof of Concept Study

This is the first study to examine if transcranial infrared laser stimulation (TILS) improves cognition in older euthymic bipolar patients, who exhibit greater cognitive decline than is expected for age-matched controls. TILS is a non-invasive novel form of photobiomodulation that augments prefrontal oxygenation and improves cognition in young adults by upregulating the mitochondrial respiratory enzyme cytochrome-c-oxidase. We used a crossover sham-controlled design to examine if TILS to bilateral prefrontal cortex produces beneficial effects on cognition in 5 euthymic bipolar patients (ages 60-85). We measured cognitive flexibility, verbal fluency, working memory, sustained attention and impulsivity with tasks that have been shown to differentiate between healthy older adults and older bipolar adults. We found TILS-induced improvements in cognitive performance on the tasks that measure cognitive flexibility and impulsivity, after 5 weekly sessions of TILS. We concluded that TILS appeared both safe and effective in helping alleviate the accelerated cognitive decline present in older bipolar patients.

Sex differences in the blood-brain barrier: Implications for mental health

Prevalence of mental disorders, including major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ) are increasing at alarming rates in our societies. Growing evidence points toward major sex differences in these conditions, and high rates of treatment resistance support the need to consider novel biological mechanisms outside of neuronal function to gain mechanistic insights that could lead to innovative therapies. Blood-brain barrier alterations have been reported in MDD, BD and SZ. Here, we provide an overview of sex-specific immune, endocrine, vascular and transcriptional-mediated changes that could affect neurovascular integrity and possibly contribute to the pathogenesis of mental disorders. We also identify pitfalls in current literature and highlight promising vascular biomarkers. Better understanding of how these adaptations can contribute to mental health status is essential not only in the context of MDD, BD and SZ but also cardiovascular diseases and stroke which are associated with higher prevalence of these conditions.

Call to action regarding the vascular-bipolar link: A report from the Vascular Task Force of the International Society for Bipolar Disorders

OBJECTIVES

The association of bipolar disorder with early and excessive cardiovascular disease was identified over a century ago. Nonetheless, the vascular-bipolar link remains underrecognized, particularly with regard to how this link can contribute to our understanding of pathogenesis and treatment.

METHODS

An international group of experts completed a selective review of the literature, distilling core themes, identifying limitations and gaps in the literature, and highlighting future directions to bridge these gaps.

RESULTS

The association between bipolar disorder and vascular disease is large in magnitude, consistent across studies, and independent of confounding variables where assessed. The vascular-bipolar link is multifactorial and is difficult to study given the latency between the onset of bipolar disorder, often in adolescence or early adulthood, and subsequent vascular disease, which usually occurs decades later. As a result, studies have often focused on risk factors for vascular disease or intermediate phenotypes, such as structural and functional vascular imaging measures. There is interest in identifying the most relevant mediators of this relationship, including lifestyle (eg, smoking, diet, exercise), medications, and systemic biological mediators (eg, inflammation). Nonetheless, there is a paucity of treatment studies that deliberately engage these mediators, and thus far no treatment studies have focused on engaging vascular imaging targets.

CONCLUSIONS

Further research focused on the vascular-bipolar link holds promise for gleaning insights regarding the underlying causes of bipolar disorder, identifying novel treatment approaches, and mitigating disparities in cardiovascular outcomes for people with bipolar disorder.

Altered biochemical metabolism and its lateralization in the cortico-striato-cerebellar circuit of unmedicated bipolar II depression

OBJECTIVES

Evidence of the relationship between neurometabolic changes in the cortico-striato-cerebellar (CSC) circuit and bipolar disorder (BD) is still limited. To elucidate the pathogenesis of BD, we investigated the underlying neurometabolic changes and their effect on CSC lateralization circuits in unmedicated patients with bipolar II depression.

METHODS

Forty unmedicated participants with bipolar II depression and forty healthy controls underwent proton magnetic resonance spectroscopy (¹H-MRS). We obtained bilateral metabolic ratios of N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr in the prefrontal white matter (PWM), anterior cingulate cortex (ACC), basal ganglia (BG) and the cerebellum. Metabolic ratios were characterized using a laterality index (LI) for left-right asymmetry.

RESULTS

Overall, aberrant lateralization in the CSC circuit was characteristic in patients with bipolar II depression. Patients with bipolar II depression showed significantly lower NAA/Cr ratios in the left PWM, right ACC, left BG and left cerebellum when compared with the healthy controls. For bipolar II depression, we found lower NAA/Cr LI in the PWM, BG, and cerebellum, higher NAA/Cr LI in the ACC, and higher Cho/Cr LI in the BG and cerebellum when compared to the standard value (1.0). For healthy controls, we found lower NAA/Cr LI only in the BG and higher Cho/Cr LI in the cerebellum when compared to 1.0.

LIMITATIONS

As a cross-sectional study with a small sample size, progressive changes and complex metabolic interactions with treatment were not observed.

CONCLUSIONS

Our findings suggest that abnormal biochemical metabolism with aberrant lateralization in the CSC circuit may be an underlying pathophysiology of bipolar II depression.

Cerebral blood flow in bipolar disorder: A systematic review

BACKGROUND

Neuroimaging of cerebral blood flow (CBF) can inform our understanding of the pathophysiology of bipolar disorder (BD) as there is increasing support for the concept that BD is in part a vascular disease. Despite numerous studies examining CBF in BD, there has not yet been a review of the literature on the topic of CBF in BD.

METHODS

A systematic review of the literature on CBF in BD was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Studies included measured CBF by single-photon emission computerized tomography (SPECT), positron emission tomography (PET), arterial spin labelling (ASL) or perfusion weighted imaging (PWI) in a group of BD patients.

RESULTS

Thirty-three studies with a total of 508 subjects with BD and 538 controls were included (n = 15 SPECT; n = 8 PET; n = 7 ASL; n = 1 PWI; n = 2 other). The majority of studies in BD depression and mania reported widespread resting hypoperfusion in cingulate gyrus, frontal, and anterior temporal regions in comparison to healthy controls (HC). Findings in euthymic BD subjects and in symptomatically heterogeneous groups were less consistent. Studies that examined CBF responses to cognitive or emotional stimuli in BD subjects have reported hypoperfusion or different regions involved in comparison to HC.

LIMITATIONS

Important methodological heterogeneity between studies, and small number of subjects per study.

CONCLUSIONS

The most consistent findings to date are hypoperfusion in BD mood episodes, and hypoactive CBF responses to emotional or cognitive challenges. Future studies examining CBF are warranted, including prospective studies, studies examining CBF as a treatment target, and multimodal imaging studies.

Spatially adaptive unsupervised multispectral nonlocal filtering for improved cerebral blood flow mapping using arterial spin labeling magnetic resonance imaging

BACKGROUND

Cerebral blood flow (CBF) is an emerging biomarker for normal aging and neurodegenerative diseases. Arterial spin labeling (ASL) perfusion MRI permits noninvasive quantification of CBF. However, high-quality mapping of CBF from ASL imaging is challenging, largely due to noise.

NEW METHOD

We demonstrate the ability of the recently introduced nonlocal estimation of multispectral magnitudes (NESMA) filter to greatly improve determination of CBF estimates from ASL imaging data. We evaluated the results of NESMA-ASL for CBF mapping from data obtained on human brain (n = 10) across a wide age range (21-74 years) using a standard clinical protocol. Results were compared to those obtained from unfiltered images or filtered images using conventional and advanced filters. Quantitative analyses for different spatial image resolutions and signal-to-noise ratios, SNRs, were also conducted.

RESULTS

Our results demonstrate the potential of NESMA-ASL to permit high-quality high-resolution CBF mapping. NESMA-ASL substantially reduces random variation in derived CBF estimates while preserving edges and small structures, with minimal bias and dispersion in derived CBF estimates.

COMPARISON WITH EXISTING METHODS

NESMA-ASL outperforms all evaluated filters in terms of noise reduction and detail preservation. Further, unlike other filters, NESMA-ASL is straightforward to implement requiring only one user-defined parameter, which is relatively insensitive to SNR or local image structure.

CONCLUSIONS

In-vivo estimation of CBF in the human brain from ASL imaging data was markedly improved through use of the NESMA-ASL filter. The use of NESMA-ASL may contribute significantly to the goal of high-quality high-resolution CBF mapping within a clinically feasible acquisition time.

Decreased cerebral blood flow in the primary motor cortex in major depressive disorder with psychomotor retardation

Psychomotor retardation (PMR) is one of the core symptoms of major depressive disorder (MDD) and has a specific pathophysiology, but studies of PMR remains sparse. The purpose of this study was to explore the cerebral blood flow (CBF) of PMR in MDD. One-hundred-seven antidepressant-free MDD patients and 48 normal controls (NCs) were recruited for this study. All subjects underwent arterial spin labeling-magnetic resonance imaging (ASL-MRI) for the CBF calculation. MDD patients were divided into the PMR group (N=35) and NPMR (non-PMR) group (N=72) according to the Salpetriere Retardation Rating Scale (SRRS) score. After a baseline MRI scan, patients began to receive antidepressant treatment. Thirty-nine patients (15 PMR, 24 NPMR) who were remitted after 8weeks participated in the follow-up MRI scan. For statistical analysis, subjects with unqualified MRI image and unmatched demographic data were ruled out. Consequently, 30 NCs and 60 patients (30 PMR, 30 NPMR) at baseline as well as 22 patients (11 PMR, 11 NPMR) at follow-up underwent statistical analysis. The PMR group showed significantly decreased CBF in the right primary motor cortex (PMC) at baseline, and the CBF value of the right PMC was significantly correlated with the SRRS score, whereas the CBF of the right PMC was increased in the PMR group at follow-up compared with the baseline in longitudinal comparison. Our findings suggest that the CBF of the right PMC is a potential biomarker of PMR in MDD.

Aberrant Neural Activity in Patients With Bipolar Depressive Disorder Distinguishing to the Unipolar Depressive Disorder: A Resting-State Functional Magnetic Resonance Imaging Study

This study aims to explore the intrinsic patterns of spontaneous activity of bipolar depression (BD) patients by analyzing the fractional amplitude of low frequency fluctuation (fALFF) that help differentiate BD from unipolar depressive disorder(UD). Twenty eight patients with BD, 47 patients with UD and 29 healthy controls were enrolled to receive the resting-state functional magnetic resonance imaging (rs-fMRI) scans. The group differences of fALFF values were calculated among three groups. In addition, the correlations between the clinical variables and mfALFF values were estimated. The brain regions with activation discrepancies among three groups are located in precuneus, the left middle temporal gyrus (MTG) and left inferior parietal lobe (IPL) and lingual gyrus. Compared with HC group, BD group shows decreased fALFF in precuneus, the left IPL and increased fALFF in lingual gyrus remarkably; UD group shows significantly decreased fALFF in precuneus, the left MTG and the left IPL. On the contrast of patients with UD, patients with BD have significantly increased fALFF value in the left precuneus, the left MGT and lingual gyrus. Furthermore, a negative correlation is found between the mfALFF values in precuneus and the scores of cognitive impairment factor in the UD group. The similar pattern of intrinsic activity in PCC suggests depressive state-dependent change. The aberrant patterns of intrinsic activity in precuneus, the IPL and lingual gyrus might be provide quantitative nodes that help to conduct further study for better distinguishing between BD and UD.

Steeper Slope of Age-Related Changes in White Matter Microstructure and Processing Speed in Bipolar Disorder

OBJECTIVES

Bipolar disorder (BD) is associated with compromised white matter (WM) integrity and deficits in processing speed (PS). Few studies, however, have investigated age relationships with WM structure and cognition to understand possible changes in brain health over the lifespan. This investigation explored whether BD and healthy counterpart (HC) participants exhibited differential age-related associations with WM and cognition, which may be suggestive of accelerated brain and cognitive aging.

DESIGN

Cross-sectional study.

SETTING

University of California San Diego and the Veterans Administration San Diego Healthcare System.

PARTICIPANTS

33 euthymic BD and 38 HC participants.

MEASUREMENTS

Diffusion tensor imaging was acquired as a measure of WM integrity, and tract-specific fractional anisotropy (FA) was extracted utilizing the Johns Hopkins University probability atlas. PS was assessed with the Number and Letter Sequencing conditions of the Delis-Kaplan Executive Function System Trail Making Test.

RESULTS

BD participants demonstrated slower PS compared with the HC group, but no group differences were found in FA across tracts. Multiple linear regressions revealed a significant group-by-age interaction for the right uncinate fasciculus, the left hippocampal portion of the cingulum, and for PS, such that older age was associated with lower FA values and slower PS in the BD group only. The relationship between age and PS did not significantly change after accounting for uncinate FA, suggesting that the observed age associations occur independently.

CONCLUSIONS

Results provide support for future study of the accelerated aging hypothesis by identifying markers of brain health that demonstrate a differential age association in BD.

A comparison of neurometabolites between remitted bipolar disorder and depressed bipolar disorder: A proton magnetic resonance spectroscopy study

BACKGROUND

Recent many studies found the abnormal neurometabolites in the acute bipolar disorder (BD). However, limited studies were to detect neurometabolites in remitted BD, comparison between acute and remitted BD is conductive to understand the outcome of neurometabolites. This study sought to investigate the differences in neurometabolites between remitted and depressed BD patients using proton magnetic resonance spectroscopy (¹H-MRS).

METHODS

Three subject groups were enrolled: 22 remitted BD patients, 22 depressed BD patients and 24 healthy controls. All subjects underwent ¹H-MRS to measure N-acetylaspartate (NAA), Choline (Cho), myo-Inositol (mI) and Creatine (Cr) of several bilateral areas potentially involved in BD: prefrontal whiter matter (PWM), thalamus and putamen. The neurometabolite ratios were compared among three groups. The correlations between abnormal neurometabolite ratios and clinical data were computed.

RESULTS

The lower bilateral PWM NAA/Cr ratios were found in depressed BD patients than remitted BD patients and healthy controls, no differences were found between the remitted BD patients and controls. For depressed BD patients, left PWM NAA/Cr ratios showed negative correlation with age of onset, right PWM NAA/Cr ratios showed positive correlation with duration of illness.

CONCLUSIONS

Our findings suggest the abnormal neurometabolites in the prefrontal lobe whiter may occur in the depressed BD. The remitted BD may resemble healthy subjects in terms of neurometabolites. In addition, abnormal neurometabolites in prefrontal lobe whiter may correlate with the age of onset and illness length.

Bipolar Patients with Vascular Risk Display a Steeper Age-Related Negative Slope in Inhibitory Performance but Not Processing Speed: A Preliminary Study

OBJECTIVE

Bipolar disorder (BD) is associated with cognitive deficits, yet little is known about associations between cognition, vascular risk (VR), and age in this population. This study investigated whether BD patients with VR demonstrate stronger apparent age-related decline in inhibitory performance and processing speed (PS).

METHODS

A full medical history was obtained for 34 euthymic BD and 41 healthy comparison (HC) individuals. The Delis-Kaplan Executive Functions Color Word Interference Subtests were administered to all participants to assess for inhibitory performance (condition 3) and PS (conditions 1 and 2). VR positive (VRPos) and VR negative (VRNeg) groups were created based on the presence of one or more VR factors.

RESULTS

VRPos-BD participants demonstrated significantly worse inhibitory performance with older age, whereas age and inhibition were not significantly related in the VRPos-HC group or in those who were VRNeg. The same was not true for PS.

CONCLUSION

BD patients with VR may also be at risk for greater decline in inhibitory performance, but not PS, with age. Longitudinal studies are needed to further investigate the contributions of VR to cognitive decline among older BD patients.

Distinct resting-state perfusion patterns underlie psychomotor retardation in unipolar vs. bipolar depression

OBJECTIVE

Psychomotor abnormalities characterize both unipolar (UP) depression and bipolar (BP) depression. We aimed to assess their neurobiological correlates in terms of motor activity (AL) and resting-state cerebral blood flow (rCBF) and investigate their association in BP, UP, and healthy controls (HC).

METHOD

We enrolled 42 depressed patients (22 BP, 20 UP) and 19 HC matched for age, gender, education, income. AL and rCBF were objectively assessed with the use of wrist actigraphy and arterial spin labeling. Group differences and the association of AL and rCBF were computed.

RESULTS

Activity level was significantly reduced in patients, but no difference was found between BP and UP. Increased perfusion was found in BP compared with UP and HC, in multiple brain areas. We found positive correlations of rCBF and AL in BP and UP, in different parts of the insula and frontal regions. Only BP showed a cluster in the left precentral gyrus. In HC, only inverse correlations of AL and rCBF were found.

CONCLUSION

The differences in rCBF and in the localization of the clusters of positive AL/rCBF correlations between BP and UP suggest that different neural impairments may underlie motor symptoms in the two disorders, but finally converge in phenotypically similar manifestations.

Extraversion modulates functional connectivity hubs of resting-state brain networks

Personality dimension extraversion describes individual differences in social behaviour and socio-emotional functioning. The intrinsic functional connectivity patterns of the brain are reportedly associated with extraversion. However, whether or not extraversion is associated with functional hubs warrants clarification. Functional hubs are involved in the rapid integration of neural processing, and their dysfunction contributes to the development of neuropsychiatric disorders. In this study, we employed the functional connectivity density (FCD) method for the first time to distinguish the energy-efficient hubs associated with extraversion. The resting-state functional magnetic resonance imaging data of 71 healthy subjects were used in the analysis. Short-range FCD was positively correlated with extraversion in the left cuneus, revealing a link between the local functional activity of this region and extraversion in risk-taking. Long-range FCD was negatively correlated with extraversion in the right superior frontal gyrus and the inferior frontal gyrus. Seed-based resting-state functional connectivity (RSFC) analyses revealed that a decreased long-range FCD in individuals with high extraversion scores showed a low long-range functional connectivity pattern between the medial and dorsolateral prefrontal cortex, middle temporal gyrus, and anterior cingulate cortex. This result suggests that decreased RSFC patterns are responsible for self-esteem, self-evaluation, and inhibitory behaviour system that account for the modulation and shaping of extraversion. Overall, our results emphasize specific brain hubs, and reveal long-range functional connections in relation to extraversion, thereby providing a neurobiological basis of extraversion.