The hippocampus and executive functions in depression

Abnormal dynamic functional connectivity of hippocampal subregions associated with working memory impairment in melancholic depression

BACKGROUND

Previous studies have demonstrated structural and functional changes of the hippocampus in patients with major depressive disorder (MDD). However, no studies have analyzed the dynamic functional connectivity (dFC) of hippocampal subregions in melancholic MDD. We aimed to reveal the patterns for dFC variability in hippocampus subregions - including the bilateral rostral and caudal areas and its associations with cognitive impairment in melancholic MDD.

METHODS

Forty-two treatment-naive MDD patients with melancholic features and 55 demographically matched healthy controls were included. The sliding-window analysis was used to evaluate whole-brain dFC for each hippocampal subregions seed. We assessed between-group differences in the dFC variability values of each hippocampal subregion in the whole brain and cognitive performance on the MATRICS Consensus Cognitive Battery (MCCB). Finally, association analysis was conducted to investigate their relationships.

RESULTS

Patients with melancholic MDD showed decreased dFC variability between the left rostral hippocampus and left anterior lobe of cerebellum compared with healthy controls (voxel p < 0.005, cluster p < 0.0125, GRF corrected), and poorer cognitive scores in working memory, verbal learning, visual learning, and social cognition (all p < 0.05). Association analysis showed that working memory was positively correlated with the dFC variability values of the left rostral hippocampus-left anterior lobe of the cerebellum (r = 0.338, p = 0.029) in melancholic MDD.

CONCLUSIONS

These findings confirmed the distinct dynamic functional pathway of hippocampal subregions in patients with melancholic MDD, and suggested that the dysfunction of hippocampus-cerebellum connectivity may be underlying the neural substrate of working memory impairment in melancholic MDD.

Neurochemical correlates of cognitive functions in euthymic patients with bipolar disorder: 1H-MRS study

OBJECTIVES

We assessed and correlated neurochemical levels and cognitive functions in left dorsolateral prefrontal cortex (DLPFC) and left hippocampus in euthymic patients with bipolar disorder and compared these with healthy controls METHODOLOGY: Twenty-five right-handed euthymic patients (HAM-D score < 7, and YMRS score < 7) with bipolar disorder and 20 age and gender matched controls were compared for neurometabolites (n-acetylaspartate - tNAA, choline - Cho, creatinine - Cr, myoinositol - Ins, and glutamine/glutamate - Glu/Gln) measured in left DLPFC and left hippocampus using single voxel magnetic resonance spectroscopy (MRS) and cognitive functions assessed using trail making test (TMT - A and B), wisconsin card sorting test (WCST), and wechsler memory scale (WMS-III Indian adaptation).

RESULTS

The two groups were comparable on socio-demographic variables. tNAA levels in DLPFC and hippocampus, and glutamate levels in hippocampus were found to be significantly lower and Inositol and glutamine levels in hippocampus were found to be significantly higher in patients as compared to controls. Patients performed significantly poorly as compared to controls on TMT A & B, all subscales of WMS - III, 5 subscales of WCST, including perseverative responses and errors. The tNAA and glutamate levels in left DLPFC in patients correlated with scores on TMT A & B, and several subscales of WCST and WMS-III. tNAA concentration in left hippocampus in patients correlated with scores on subscales of WMS-III.

CONCLUSION

Neurochemical dysfunction in select brain areas directly correlates with impairment in cognitive functions seen in patients with bipolar disorder in euthymic phase.

Rosmarinic acid relieves LPS-induced sickness and depressive-like behaviors in mice by activating the BDNF/Nrf2 signaling and autophagy pathway

Neuroinflammation is one of the main causes of sickness and depressive-like behavior. Rosmarinic acid (RA) has been shown to have a significant anti-neuroinflammatory effect. However, the protective effects and the underlying mechanism of RA on sickness and depressive-like behavior under conditions of neuroinflammation are still unclear.　In the present study,　we investigated the effects and　the underlying mechanism of RA on lipopolysaccharide (LPS)-treated mice with sickness behavior. The behavioral effects of LPS treatment and RA administration were assessed using behavioral tests including a sucrose preference test and an open field test. The neuroprotective effects of RA in conditions of neuroinflammatory injury were determined by HE staining, Nissl staining, and immunofluorescent staining. Moreover, its underlying mechanism was analyzed by using real-time PCR analysis, western blot, and immunofluorescent analysis. The results indicated that RA dramatically mitigated sickness behaviors and histologic brain damage in mice exposed to LPS. In addition, RA administration markedly promoted the expression of brain-derived neurotrophic factor (BDNF)/erythroid 2-related factor 2 (Nrf2), the key regulatory proteins for Nrf2 activation (p21 and p62), the downstream antioxidant enzymes (HO-1, NQO1, GCLC), the autophagy-related proteins (LC3II and Beclin1), and mitochondrial respiratory enzyme genes (ME1, IDH1, 6-PGDH), while reducing the expression of pro-inflammatory genes (CD44, iNOS, TNFα, IL-1β). Moreover, the double-label immunofluorescent analysis revealed that RA increased the fluorescence intensity of LC3 mostly co-localized with neurons and co-expressed with Nrf2. Taken together, our research found that RA could effectively alleviate sickness behaviors and nerve injury caused by neuroinflammation, and its protective effects were mediated by the Nrf2 signaling pathway, which reduced cellular oxidative stress, inflammation, mitochondrial respiratory function damage, and autophagy imbalance. Therefore, RA has the potential to prevent or treat sickness and depressive-like behaviors under conditions of neuroinflammation.

Static magnetic field induces abnormality of glucose metabolism in rats' brain and results in anxiety-like behavior

In this study, fifty-four male Wistar rats were randomly divided into four groups according to the static magnetic field (SMF) intensity, namely, control, low-intensity, moderate-intensity, and high-intensity groups. The rats' whole body was exposed to a superconducting magnet exposure source. The exposure SMF intensity for the low-intensity, moderate-intensity, and high-intensity groups was 50 m T, 100 m T, and 200 m T, respectively, and the exposure time was 1 h/day for consecutive 15 days. After different exposure times, glucose metabolism in rats' brain was evaluated by micro-positron emission tomography (micro-PET), and the expression of hexokinase 1(HK1) and 6-phosphate fructokinase-1(PFK1) was detected by western blot. The exploration and locomotion abilities of the rats were evaluated by conducting open field test (OFT). Furthermore, pathological changes of rats' brain were observed under a microscope by using hematoxylin-eosin staining. PET results showed that moderate-intensity SMFs could cause fluctuant changes in glucose metabolism in rats' brain and the abnormalities were SMF intensity dependent. The expression of the two rate-limiting enzymes HK1 and PFK1 in glucose metabolism in brain significantly decreased after SMF exposure. The OFT showed that the total distance, surrounding distance, activity time, and climbing and standing times significantly decreased after SMF exposure. The main pathological changes in the brain were pyknosis, edema of neurons, and slight widening of the perivascular space, which occurred after 15 times of exposure. This study indicated that SMF exposure could lead to abnormal glucose metabolism in the brain and might result in anxiety-like behaviors.

Association between cognitive quotient test score and hippocampal volume: a novel, rapid application-based screening tool

We aimed to develop a brief, preclinical test to screen the reduced hippocampal volume that is a marker of early dementia [Cognitive Quotient (CQ) test]. We performed an observational study of adult subjects who underwent brain MRI in seven institutions from February 2018 to May 2019. The CQ test consists of five components: (1) digits forward, (2) digits backward, (3) Stroop test, (4) simple calculation, and (5) mental rotation. The primary outcome measure was hippocampal volume. We separated the data into derivation (n = 322) and validation cohorts (n = 96). In the derivation cohort, we built two scoring systems using the results of CQ test (model 1 and 2). In the validation cohort, we validated the correlation of the scoring systems with hippocampal volume. In the derivation cohort, there was a moderate correlation between the scoring systems and hippocampal volume [e.g., correlation coefficient = 0.62 in model 1 (95% CI 0.44–0.75)]. Likewise, in the validation cohort, there was a moderate correlation between the scoring systems and hippocampal volume [e.g., correlation coefficient = 0.54 in model 2 (95% CI 0.38–0.67)]. In this analysis of 418 participants, the score of newly developed CQ test was correlated with hippocampal volume.

Risk factors for neurocognitive impairment in patients with benign intracranial lesions

This study was designed to assess risk factors for neurocognitive impairment in patients with benign intracranial lesions including tumors and vascular lesions. 74 patients (29 m, 51 f, mean age 54.4 years) with surgery for benign intracranial lesions were included in this prospective single-center study. Extensive neuropsychological testing was performed preoperatively, including tests for attention, memory and executive functions. Furthermore, headache and depression were assessed using the german version of the HDI (IBK) and the BDI-II. Multiple linear regression analyses of the percentile ranks (adjusted for age, sex and education) including the parameters age, Karnofsky Performance Status Scale (KPS), mood, pain and lesion size were performed to identify risk factors for cognitive impairment. Using the Mann-Whitney U test, the influence of hemisphere and type of lesion (tumor/vascular) was assessed. Posthoc Bonferroni correction was performed. Poorer neurocognitive functions were observed only in the category attention in patients with higher age (divided attention, WMS) and reduced KPS (WMS). Lesion volume, mood, pain, hemisphere or the type of the lesion (tumor, vascular) were not identified as risk factors for poorer neurocognitive functions in patients with benign intracranial lesions. Age and KPS are the main risk factors for poorer neurocognitive functions in the category attention in patients with benign intracranial lesions. Knowledge of these risk factors might be important to find appropriate therapy regimes to improve cognitive functions and quality of life.

MIF 173 G>C variation was associated with depressive disorder in type 2 diabetes in an Iranian population

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a continuous metabolic disease linked with increased rate of mortality and morbidity. High levels of glucose can damage organs including kidneys, eyes, and the nervous system. Individuals with T2DM have a high prevalence of major depression. One possible question we aimed to address was the extent of co-occurrence of diabetes and depression resulting from correlated genetic risk factors.

OBJECTIVES

The current study aimed to investigate the possible associations between the macrophage migration inhibitory factor (MIF) functional variant and the risk of developing depression in T2DM patients.

PATIENTS AND METHODS

The study groups consisted of 120 patients with T2DM and comorbid depression and 120 patients with T2DM, without depression, who were recruited from the same region. Genotyping of the MIF -173 G > C (rs755622) variant was performed using Polymerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP). In addition, the level of MIF expression was comparatively evaluated in both groups by quantitative real-time PCR.

RESULT

The data showed that the presence of C allele (GC + CC vs. GG) might predispose females to depression in patients with T2DM. In addition, patients with T2DM carrying at least one C allele showed significantly elevated levels of MIF RNA expression in comparison to individuals with GG genotype.

CONCLUSION

MIF variant could be considered as a factor making female patients with T2DM vulnerable to depression. So, this might be an important result for precise diagnosis and/or earlier treatment.

Hippocampal alterations and functional correlates in adolescents and young adults with congenital heart disease

There is a high prevalence of neurodevelopmental impairments in individuals living with congenital heart disease (CHD) and the neural correlates of these impairments are not yet fully understood. Recent studies have shown that hippocampal volume and shape differences may provide unique biomarkers for neurodevelopmental disorders. The hippocampus is vulnerable to early life injury, especially in populations at risk for hypoxemia or hemodynamic instability such as in neonates with CHD. We compared hippocampal gray and white matter volume and morphometry between youth born with CHD (n = 50) aged 16-24 years and healthy peers (n = 48). We also explored whether hippocampal gray and white matter volume and morphometry are associated with executive function and self-regulation deficits. To do so, participants underwent 3T brain magnetic resonance imaging and completed the self-reported Behavior Rating Inventory of Executive Function-Adult version. We found that youth with CHD had smaller hippocampal volumes (all statistics corrected for false discovery rate; q < 0.05) as compared to controls. We also observed significant smaller surface area bilaterally and inward displacement on the left hippocampus predominantly on the ventral side (q < 0.10) in the CHD group that were not present in the controls. Left CA1 and CA2/3 were negatively associated with working memory (p < .05). Here, we report, for the first-time, hippocampal morphometric alterations in youth born with CHD when compared to healthy peers, as well as, structure-function relationships between hippocampal volumes and executive function. These differences may reflect long lasting alterations in brain development specific to individual with CHD.

Depression related cerebral pathology and its relationship with cognitive functioning: A systematic review

BACKGROUND

Depression's relationship with cerebral abnormalities and cognitive decline is temporally dynamic. Despite clear clinical utility, understanding depression's effect on cerebral structures, cognitive impairment and the interaction between these symptoms has had limited consideration.

METHODS

This review summarised studies examining a clinical depression diagnosis or validated scales measuring depressive symptoms, data concerning amyloid-beta (Aβ) levels, brain structure and function focusing on hippocampal alterations, or white matter hyperintensities (WMH), and at least one validated neuropsychological test. Online database searches of: PsycINFO, EMBASE, MEDLINE, and Scopus were conducted to identify potential articles.

RESULTS

While depression was consistently associated with cross-sectionally cognitive decline across multiple domains, the neuropathological basis of this dysfunction remained unclear. Hippocampal, frontal, and limbic dysfunction as well as cortical thinning, WMH, and Aβ burden all provide inconsistent findings, likely due to depression subtypes. The consistency of these findings additionally decreases when examining this relationship longitudinally, as these results are further confounded by pre-dementia states. The therapeutic interventions examined were more efficacious in the younger compared with the older samples, who were characterised by greater WMH and Aβ burden.

LIMITATIONS

The limited number of longitudinal and interventional studies in addition to the heterogeneity of the samples restricts their generalisability.

CONCLUSIONS

Symptomatological differences between early-onset and late-onset depression (EOD and LOD) appear crucial in understanding whether late-life depression is the primary or secondary source of cerebral pathology. Though severe cognitive impairments and clearer neuropathological underpinnings are more characteristic of LOD than EOD, the inconsistency of valid biomarkers remains problematic.

Antidepressant-like effects of paeoniflorin on post-stroke depression in a rat model

BACKGROUND

Post-stroke depression (PSD) is one of the most prevalent emotional disorders after stroke and often results in poor outcomes. However, the underlying physiopathologic mechanism and effective treatment of PSD remain poorly elucidated.

OBJECTIVE

To investigate whether paeoniflorin has antidepressant-like activity in a rat model of PSD.

METHODS

Rats were randomly divided into four groups: sham-operated control (Sham), PSD, paeoniflorin (with PSD) and fluoxetine group(with PSD). PSD was developed by the right middle cerebral artery occlusion followed 21 days chronic unpredictable mild stress combined (CUMS) with raised alone. Tests of sucrose preference and open field were used to assess the depression-like behavior. Neurological function was evaluated by neurological deficit score and beam balance test. Expression of phosphorylated CREB (p-CREB) and brain-derived neurotrophic factor (BDNF) in the CA1 region of the hippocampal complex was evaluated by western blot and immunofluorescence.

RESULTS

Te depressive-like behaviors markedly improved after paeoniflorin and fluoxetine treatment. Furthermore, paeoniflorin treatment significantly increased BDNF and p-CREB expression in the CA1 region.

CONCLUSIONS

Observed results suggested that paeoniflorin could ameliorate the symptoms and improve the functional capability of PSD rats, similar to the effect of fluoxetine.

ABBREVIATIONS

PSD: post-stroke depression; CUMS: chronic unpredictable mild stress stimulation; MCAO: middle cerebral artery occlusion; OFT: open field test; SPT: sucrose preference test, NDS: neurological deficit score, BBT: beam balance test; BDNF: brain-derived neurotrophic factor protein; p-CREB: phosphorylated Cyclic-AMP responsive element binding protein.

Decreased cerebral blood flow and improved cognitive function in patients with end-stage renal disease after peritoneal dialysis: An arterial spin-labelling study

OBJECTIVES

The aim of this study was to evaluate the relationship between cognitive impairment and brain perfusion using arterial spin labelling (ASL) in end-stage renal disease (ESRD) patients undergoing PD.

METHODS

ESRD patients undergoing PD were recruited. Laboratory screening, neuropsychological tests and ASL magnetic resonance imaging (MRI) were conducted prior to and after 6 months of PD. Age- and sex-matched normal subjects without ESRD served as the control group. Comparisons of regional CBF between ESRD patients before or after undergoing PD and normal controls were performed. Correlations between biochemical, neuropsychological and CBF data were also conducted to evaluate the relationships.

RESULTS

ESRD patients showed poor performance in many of the neuropsychological tests; PD improved cognition in some domains. Pre-PD patients had higher mean CBF than post-PD patients and normal controls, but no significant difference was found between the normal controls and post-PD patients. Negative correlations were observed pre-PD (regional CBF in left hippocampus vs. perseverative responses, r = -0.662, p = 0.014), post-PD (mean CBF vs. haemoglobin level, r = -0.766, p = 0.002), and before and after PD (change in CBF in the left putamen vs. change in haematocrit percentage, r = -0.808, p = 0.001).

CONCLUSION

Before PD, ESRD patients had increased cerebral perfusion that was related to poorer executive function, especially in the left hippocampus. Post-PD patients performed better in some cognitive test domains than pre-PD patients. The degree of anaemia, i.e., haemoglobin level or haematocrit percentage, might predict cognitive impairment in PD patients.

KEY POINTS

• In this study, ESRD patients before PD had cerebral hyperperfusion that was related to poorer executive function. • Post-PD patients performed better in some cognitive test domains than pre-PD patients did. • The degree of anaemia might predict cognitive impairment in PD patients.

Divergent Roles of Vascular Burden and Neurodegeneration in the Cognitive Decline of Geriatric Depression Patients and Mild Cognitive Impairment Patients

Both geriatric depression and mild cognitive impairment (MCI) confer an increased risk for the development of dementia. The mechanisms underlying the development of cognitive impairment in geriatric depression patients remain controversial. The present study aimed to explore the association of cognitive decline with vascular risk, white matter hyperintensity (WMH) burden and hippocampal volume in both remitted geriatric depression (RGD) subjects and amnestic mild cognitive impairment (aMCI) subjects. Forty-one RGD subjects, 51 aMCI subjects, and 64 healthy elderly subjects underwent multimodal MRI scans and neuropsychological tests at both baseline and a 35-month follow-up. According to the changing patterns (declining or stable) of global cognitive function during the follow-up period, each group was further divided into a declining subgroup and a stable subgroup. The Framingham 10-year cardiovascular risk, WMH volume and hippocampal volume were measured to assess vascular pathology and neurodegeneration, respectively. The RGD declining group displayed a higher vascular risk and greater WMH volume than the RGD stable group, whereas no such difference was found in the aMCI subjects. In contrast, the aMCI declining group displayed a smaller left hippocampal volume than the aMCI stable group, whereas no such difference was found in the RGD subjects. Furthermore, greater increases in the WHM volume correlated with greater decreases in global cognitive function in the RGD declining group, and greater decreases in the left hippocampal volume correlated with greater decreases in global cognitive function in the aMCI declining group. In conclusion, the cognitive decline in RGD patients is associated with vascular burden, whereas the cognitive decline in aMCI patients is associated with neurodegeneration. These findings could contribute to a better understanding of the specific mechanisms of the development of dementia in each condition.

Proteomic Analysis of the Hippocampus in Mouse Models of Trigeminal Neuralgia and Inescapable Shock-Induced Depression

To investigate the behavioral and biomolecular similarity between neuralgia and depression, a trigeminal neuralgia (TN) mouse model was established by constriction of the infraorbital nerve (CION) to mimic clinical trigeminal neuropathic pain. A mouse learned helplessness (LH) model was developed to investigate inescapable foot-shock-induced psychiatric disorders like depression in humans. Mass spectrometry was used to assess changes in the biomolecules and signaling pathways in the hippocampus from TN or LH mice. TN mice developed not only significant mechanical allodynia but also depressive-like behaviors (mainly behavioral despair) at 2 weeks after CION, similar to LH mice. MS analysis demonstrated common and distinctive protein changes in the hippocampus between groups. Many protein function families (such as cell-to-cell signaling and interaction, and cell assembly and organization,) and signaling pathways (e.g., the Huntington's disease pathway) were involved in chronic neuralgia and depression. Together, these results demonstrated that the LH and TN models both develop depressive-like behaviors, and revealed the involvement of many psychiatric disorder-related biomolecules/pathways in the pathogenesis of TN and LH.