Attention impairment in bipolar disorder: A systematic review

Repetitive Transcranial Magnetic Stimulation (rTMS) Treatment Reduces Variability in Brain Function in Schizophrenia: Data From a Double-Blind, Randomized, Sham-Controlled Trial

BACKGROUND/HYPOTHESIS

There is increasing awareness of interindividual variability in brain function, with potentially major implications for repetitive transcranial magnetic stimulation (rTMS) efficacy. We perform a secondary analysis using data from a double-blind randomized controlled 4-week trial of 20 Hz active versus sham rTMS to dorsolateral prefrontal cortex (DLPFC) during a working memory task in participants with schizophrenia. We hypothesized that rTMS would change local functional activity and variability in the active group compared with sham.

STUDY DESIGN

83 participants were randomized in the original trial, and offered neuroimaging pre- and post-treatment. Of those who successfully completed both scans (n = 57), rigorous quality control left n = 42 (active/sham: n = 19/23), who were included in this analysis. Working memory-evoked activity during an N-Back (3-Back vs 1-Back) task was contrasted. Changes in local brain activity were examined from an 8 mm ROI around the rTMS coordinates. Individual variability was examined as the mean correlational distance (MCD) in brain activity pattern from each participant to others within the same group.

RESULTS

We observed an increase in task-evoked left DLPFC activity in the active group compared with sham (F1,36 = 5.83, False Discovery Rate (FDR))-corrected P = .04). Although whole-brain activation patterns were similar in both groups, active rTMS reduced the MCD in activation pattern compared with sham (F1,36 = 32.57, P < .0001). Reduction in MCD was associated with improvements in attention performance (F1,16 = 14.82, P = .0014, uncorrected).

CONCLUSIONS

Active rTMS to DLPFC reduces individual variability of brain function in people with schizophrenia. Given that individual variability is typically higher in schizophrenia patients compared with controls, such reduction may "normalize" brain function during higher-order cognitive processing.

Processing speed and sustained attention in bipolar disorder and major depressive disorder: A systematic review and meta-analysis

OBJECTIVES

Cognitive impairment is a core feature of bipolar disorder (BD) and major depressive disorder (MDD). Deficits in processing speed (PS) and sustained attention (SA) may be particularly impaired and may underpin a broader profile of deficits, however current knowledge of the nature of these impairments is limited by heterogeneous results in the literature. Few reviews to date have attempted to disentangle sources of heterogeneity to assess the presence and magnitude of impairments in PS and SA in BD and MDD.

METHODS

One hundred and three studies were reviewed to examine performance in tests of PS and SA in BD (n = 3452) and MDD (n = 5461) compared to healthy controls (n = 8016). Neuropsychological methodology used in the literature was summarised. Data were meta-analysed to assess impairments in PS and SA for each neuropsychological test separately. Subgroup analysis was performed across mood states to investigate sources of heterogeneity.

RESULTS

Impairments were found across most neuropsychological tests, with small to large effect sizes for BD (range: d = 0.19-0.96) and MDD (range: d = 0.29-0.86). Impairments were present in symptomatic states and euthymia in most cases. Some outcome measures were not impaired in euthymia. Heterogeneity was observed for most neuropsychological tests and remained after separating by mood state. There inadequate data to meta-analyse some outcome measures, particularly for symptomatic groups.

CONCLUSION

Impairments in PS and SA in BD and MDD can be observed across most neuropsychological tests. Future research should further investigate the nature of these impairments across mood states, controlling for clinical confounds.

Effect of Vagus Nerve Stimulation on Attention and Working Memory in Neuropsychiatric Disorders: A Systematic Review

BACKGROUND

It has been suggested that vagus nerve stimulation (VNS) may enhance attention and working memory. The neuromodulator effects of VNS are thought to activate the release of neurotransmitters involving cognition and to promote neuronal plasticity. Therefore, VNS has been studied for its effects on attention and working memory impairment in neuropsychiatric disorders.

OBJECTIVES

This study aimed to assess the effects of VNS on attention and working memory among patients with neuropsychiatric disorders, examine stimulation parameters, provide mechanistic hypotheses, and propose future studies using VNS.

MATERIALS AND METHODS

We conducted a systematic review using electronic databases MEDLINE (Ovid), Embase (Ovid), Cochrane library, and PsycINFO (Ovid). Narrative analysis was used to describe the therapeutic effects of VNS on attention and working memory, describe stimulation parameters, and propose explanatory mechanisms.

RESULTS

We identified 20 studies reporting VNS effects on attention and working memory in patients with epilepsy or mood disorders. For epilepsy, there was one randomized controlled trial from all 18 studies. It demonstrated no statistically significant differences in the cognitive tasks between active and control VNS. From a within-subject experimental design, significant improvement of working memory after VNS was demonstrated. One of three nonrandomized controlled trials found significantly improved attentional performance after VNS. The cohort studies compared VNS and surgery and found attentional improvement in both groups. Nine of 12 pretest-posttest studies showed improvement of attention or working memory after VNS. For mood disorders, although one study showed significant improvement of attention following VNS, the other did not.

CONCLUSIONS

This review suggests that, although we identified some positive results from eligible studies, there is insufficient good-quality evidence to establish VNS as an effective intervention to enhance attention and working memory in persons with neuropsychiatric disorders. Further studies assessing the efficacy of such intervention are needed.

Functional and behavioral effects of de novo mutations in calcium-related genes in patients with bipolar disorder

Bipolar disorder is a common mental illness occurring in approximately 1% of individuals and exhibits lifetime prevalence. Although genetic factors are known to contribute to this disorder, the genetic architecture has not yet been completely clarified. Our initial trio-based exome sequencing study of bipolar disorder showed enrichment of de novo, loss-of-function (LOF) or protein-altering mutations in a combined group with bipolar I and schizoaffective disorders, and the identified de novo mutations were enriched in calcium-related genes. These findings suggested a role for de novo mutations in bipolar disorder. The validity of these statistical associations can be demonstrated if the functional impact of the mutations on cellular function and behavior are identified. In this study, we focused on two de novo LOF mutations in calcium-related genes, EHD1 and MACF1, found in patients with bipolar disorder. We first showed that the EHD1 mutation resulted in a truncated protein with diminished effect on neurite outgrowth and inhibited endocytosis. Next, we used CRISPR/Cas9 to establish two knock-in mouse lines to model the in vivo effects of these mutations. We performed behavioral screening using IntelliCage and long-term wheel running analysis. Ehd1 mutant mice showed higher activity in the light phase. Macf1 mutant mice showed diminished attention and persistence to rewards. These behavioral alterations were similar to the phenotypes in previously proposed animal models of bipolar disorder. These findings endorse the possible role of de novo mutations as a component of the genetic architecture of bipolar disorder which was suggested by the statistical evidence.

Grey and white matter alteration in euthymic children with bipolar disorder: a combined source-based morphometry (SBM) and voxel-based morphometry (VBM) study

Bipolar disorder (BPD) is a psychiatric condition driving frequent mood swings between periodic extremes of happiness and depression in patients. In this study, a source-based morphometry (SBM) and voxel-based morphometry (VBM) analysis was utilized to measure the differences in the white matter (WM) and grey matter (GM) between euthymic children with BPD and typically developing (TD) children. We adapted both multivariate (SBM) and univariate (VBM) analysis in 20 children with BPD euthymia /remission and compared to the same number of TD age-matched children. The VBM did not reveal any increase in GM and WM voxel values in children with BPD. However, a decrease in the GM voxel values in the bilateral middle frontal and WM voxels in the left hippocampus, left caudate, left orbitofrontal and right inferior parietal cortices was identified. Conversely, SBM analysis in BPD displayed a high GM value in bilateral angular gyrus, bilateral inferior temporal, left supplementary motor area and left middle temporal region, while a low value was observed in left inferior and middle occipital, cerebellum, thalamus, left premotor area and left lingual gyrus. These findings suggested a crucial GM and WM alteration in multiple neural regions in BPD children even during sustained and substantial remission.

Elated or sad mood induction affects the attention of patients with a bipolar disorder less than that of patients with a depressive disorder

Introduction: The role of acute mood states as mediating factors in cognitive impairment in patients with mania or depression is not sufficiently clear. Similarly, the extent to which cognitive impairment is trait or state-specific remains an open question. Therefore, the aim of this study was to investigate the effect of a mood-induction on attention in patients with an affective disorder.Methods: Twenty-two depressed bipolar patients, 10 manic bipolar patients, 17 with a depressive episode (MDE), and 24 healthy controls performed the Attention-Network-Test (ANT). In a within-participants design, elated and sad moods were induced by an autobiographic recall and measured on a self-report scale. Subsequently, participants performed the ANT again.Results: The modulating effect of the elated mood induction on attention was small. Only the MDE group displayed moderate improvements in selective attention and tonic alertness. Surprisingly, after the sad mood induction, patients with MDE improved moderately on phasic and tonic alertness. Phasic alertness was also enhanced in patients with mania. Finally, after the mood induction, patients with MDE showed the largest variability in attentional performance.Conclusions: Results showed only small effects of mood induction on attention. This supports the view that attention deficits reflect trait variables.

Understanding cognitive impairment in mood disorders: mediation analyses in the UK Biobank cohort

BACKGROUND

Cognitive impairment is strongly linked with persistent disability in people with mood disorders, but the factors that explain cognitive impairment in this population are unclear.

AIMS

To estimate the total effect of (a) bipolar disorder and (b) major depression on cognitive function, and the magnitude of the effect that is explained by potentially modifiable intermediate factors.

METHOD

Cross-sectional study using baseline data from the UK Biobank cohort. Participants were categorised as having bipolar disorder (n = 2709), major depression (n = 50 975) or no mood disorder (n = 102 931 and n = 105 284). The outcomes were computerised tests of reasoning, reaction time and memory. The potential mediators were cardiometabolic disease and psychotropic medication. Analyses were informed by graphical methods and controlled for confounding using regression, propensity score-based methods and G-computation.

RESULTS

Group differences of small magnitude were found on a visuospatial memory test. Z-score differences for the bipolar disorder group were in the range -0.23 to -0.17 (95% CI -0.39 to -0.03) across different estimation methods, and for the major depression group they were approximately -0.07 (95% CI -0.10 to -0.03). One-quarter of the effect was mediated via psychotropic medication in the bipolar disorder group (-0.05; 95% CI -0.09 to -0.01). No evidence was found for mediation via cardiometabolic disease.

CONCLUSIONS

In a large community-based sample in middle to early old age, bipolar disorder and depression were associated with lower visuospatial memory performance, in part potentially due to psychotropic medication use. Mood disorders and their treatments will have increasing importance for population cognitive health as the proportion of older adults continues to grow.

DECLARATION OF INTEREST

I.J.D. is a UK Biobank participant. J.P.P. is a member of the UK Biobank Steering Committee.

Clinical and Cognitive Correlates of Insight in Bipolar Disorder

Insight is greatly impaired in Bipolar Disorder (BD), especially during mania. Cognitive impairment is also present in BD. Despite that, few studies have investigated a possible association between these two aspects. The main goal of the current study is to compare BD affective states regarding performance in cognitive testing and investigate clinical and cognitive predictors for insight loss in BD. The study investigated a sample of 65 patients who were evaluated in one of the BD phases (mania, euthymia or depression). All the subjects underwent neuropsychological evaluation and completed the Insight Scale for Affective Disorders (ISAD). The relationship between level of insight and clinical/cognitive variables was analyzed through multiple regression models. No significant differences were found among BD phases regarding performance on cognitive testing. Insight was more impaired in mania then in depression or euthymia. Predictors for loss of insight were: severity of manic symptoms and impairments in selective attention (Symbol search test), divided attention (Trail making test) and inhibition (Stroop test). The sample size is a potential limitation of the current study. Nevertheless, the results suggest this had limited impact, with group differences being detected for a number of variables. The results found have important clinical importance, suggesting, for example, that rehabilitation of specific cognitive skills may improve insight in BD.

Performance of Bipolar Disorder Patients in Attention Testing: Comparison with Normal Controls and Among Manic, Depressive, and Euthymic Phases

Several studies on cognition in bipolar disorder (BD) have been developed on the last decade. Neuropsychological evaluation of attention in BD patients is fundamental since alterations in attention affect other cognitive functions. Evaluate if performance of BD patients in attention tests varies according to each phase of the disease and verify if there are differences in attention when comparing BD patients with normal controls. The study included 101 BD patients, with ages between 18 and 65 years, being 52 euthymic, 22 manic and 27 depressive, besides 30 normal controls. All subjects were evaluated though Hamilton Depression Scale, Young Mania Rating Scale and Global Assessment of Functioning, bipolar version (CGI-BP). Attention was evaluated through a neuropsychological battery. Normal controls had a better performance in selective attention tests than BD patients. No differences were found among manic, depressive and euthymic phases. Attention is markedly impaired in BD. Nevertheless, the results of this study do not imply that the severity of the attention deficit in BD patients varies according to decease phase.

The management of cognitive impairment in bipolar disorder: current status and perspectives

Bipolar disorder (BD) is associated with important cognitive deficits that persist during the periods of remission. Although these deficits seem to play an important role in the functional impairment experienced by bipolar patients, evidence regarding their clinical management is scant. We revised the databases PubMed, MEDLINE, and clinicaltrials.gov, searching for studies focusing on the pharmacological and nonpharmacological treatment of cognitive deficits among bipolar patients. In addition, a manual search of bibliographical cross-references was performed. Currently, there is no Food and Drug Administration-approved pharmacological agent for the management of cognitive deficits in BD. A number of agents have been tested in the treatment of cognitive deficits in BD, with mixed results. Nonpharmacological interventions, such as cognitive remediation and noninvasive brain stimulation techniques, seem promising, but their role has not yet been properly explored among bipolar patients. Additional studies, aiming at evaluating the efficacy of interventions combining cognitive rehabilitation and biological treatments, are highly desirable.

Insight in bipolar disorder: a comparison between mania, depression and euthymia using the Insight Scale for Affective Disorders

Objective: To evaluate whether having general insight into bipolar disorder and its symptoms is affected by the mood state of the patient, using the Insight Scale for Affective Disorders, a hetero-application scale for people with mood disorders.Methods: Ninety-five patients with bipolar disorder were evaluated and divided into different groups according to the mood state presented during assessment (i.e., euthymia, mania and depression). Sociodemographic and clinical data (Hamilton Depression Scale, Young Mania Rating Scale, and Clinical Global Impressions Scale) were recorded. Insight was evaluated using the Insight Scale for Affective Disorders.Results: Patients with bipolar disorder in mania show less insight about their condition than patients in depression or euthymia, and less insight about their symptoms than patients with depression, with the exception of awareness of weight change.Conclusions: Loss of insight during mania may have important implications for treatment compliance and adherence and needs to be taken into account in the clinical management of people with bipolar disorder.

Evaluation of cognitive function in bipolar disorder using the Brief Assessment of Cognition in Affective Disorders (BAC-A)

BACKGROUND

Although cognitive impairment is a core feature of bipolar disorder (BD) there is no instrument of choice for the assessment of bipolar patients. The aim of this study is to assess cognitive performance using the Brief Assessment of Cognition in Affective Disorders (BAC-A), a comprehensive test battery developed specifically for BD, and determine its suitability to estimate global functioning.

METHODS

The BAC-A was administered to 93 BD patients (M ± S.E: 35.18 ± 1.39 years) and 56 healthy controls (HC - M ± S.E: 36.17 ± 1.91 years). The scores of the BAC-A were combined in eight summary scores: visuomotor, immediate affective and non-affective memory, verbal fluency, delayed affective and non-affective memory, inhibition, and problem solving. Post hoc analyses were performed on subtests of the summary scores found to be significantly different between BD patients and HC. Correlational analyses explored the association between the Global Assessment of Functioning (GAF) score and cognitive functioning.

RESULTS

Compared to HC, BD patients showed a significant impairment in short-term non-affective memory and verbal fluency. Poorer performance in verbal memory and verbal fluency summary scores correlated positively with reduced GAF.

CONCLUSIONS

Our results are consistent with previous reports of verbal memory and verbal fluency impairment in BD. The deficits in short-term memory and semantic fluency may indicate inefficient learning strategies and/or difficulties in retrieving information. The BAC-A could be used to estimate global functioning in BD patients.

Emotion regulation strategies can predict task-switching abilities in euthymic bipolar patients

This study examined task-switching abilities and emotion regulation strategies in euthymic bipolar patients (EBP). Forty EBP and 40 healthy individuals performed face categorization tasks where they switched between emotion and non-emotion (i.e., gender) features among faces and completed emotion regulation questionnaire (Gross and John, 2003). Subject groups showed substantial differences in task-switching abilities and emotion regulation strategies: (1) there was a dissociation between emotion and gender classification in EBP. The switch cost was larger [i.e., higher reaction times (RTs) on switch as compared to no-switch trials] for gender categorization as compared to the emotion categorization task. In contrast, such asymmetries were absent among healthy participants. The differential pattern of task switching reflected functional disturbances in frontotemporal neural system and an attentional bias to emotion features of the faces in EBP. This suggests that when a euthymic bipolar patient is preoccupied with emotion recognition, an instruction to perform gender categorization results in greater cost on RTs. (2) In contrast to healthy individuals, EBP reported more frequent use of emotion suppression and lesser use of cognitive reappraisal as emotion regulation strategy. (3) Emotion regulation was found to be a significant predictor of task-switching abilities. It is argued that task switching deficits rely on maladaptive emotion regulation strategies in EBP specifically when tasks of emotional significance are involved.

O insight no transtorno bipolar: uma revisão sistemática

Objetivos Realizar uma revisão sistemática para compreender que fatores estão relacionados a uma maior ou menor consciência de morbidade no transtorno bipolar (TB), como o insight varia em função do estado afetivo e estabelecer uma comparação com outros transtornos mentais. Métodos Realizou-se uma revisão sistemática da literatura científica sobre o insight em pacientes com TB. Foram buscados estudos clínicos originais sobre o tema nas bases de dados Medline, ISI e SciELO. Os termos de busca empregados foram: “insight” OR “awareness” AND “bipolar” OR “mania” OR “manic”. Resultados Foram selecionados 55 artigos. O insight no TB parece ser mais prejudicado do que na depressão unipolar, porém menos do que na esquizofrenia. Com relação ao TB, um menor nível de insight está relacionado à presença de sintomas psicóticos e de alterações cognitivas. Além disso, um comprometimento do insight está associado a uma menor adesão ao tratamento. Por outro lado, uma maior preservação do insight pode estar associada a maior ideação suicida. Finalmente, a fase maníaca cursa com um nível inferior de insight quando comparada à fase depressiva ou de eutimia. Conclusão No TB, o insight está significativamente prejudicado, especialmente na mania. Diversos fatores clínicos parecem influenciar o nível de insight.