Clinical and treatment-related predictors of cognition in bipolar disorder: focus on visual paired associative learning

Characterisation of Deficits and Sex Differences in Verbal and Visual Memory/Learning in Bipolar Disorder

OBJECTIVE

Cognitive impairment is consistently reported in bipolar disorder (BD), but few studies have characterised which memory component processes are affected. Further, it is unknown whether the component processes underlying memory impairment are moderated by sex. The present study examined diagnosis and sex differences in both verbal and visual memory/learning domains in patients with BD and psychiatrically healthy controls.

METHOD

Verbal and visual memory/learning were measured using the Hopkins Verbal Learning Test-Revised (HVLT-R) and Brief Visuospatial Memory Test-Revised (BVMT-R). 114 patients with BD (n = 50 males, n = 64 females), were compared to 105 psychiatrically healthy controls (n = 42 males, n = 63 females).

RESULTS

Patients with BD had worse performance in verbal and visual immediate and total recall, verbal and visual delayed free recall, and verbal recognition discrimination scores, but there were no group differences in learning slopes and cumulative learning index scores. There were trends for BD females to outperform BD males in visual memory/learning free recall and cumulative learning, but these results did not survive multiple testing correction. These findings did not change in a secondary sensitivity analysis comparing only strictly euthymic BD patients to controls (n = 64).

CONCLUSION

The present study found trait-like verbal and visual memory/learning impairment in BD that was attributable to deficient encoding and/or consolidation processes rather than deficits in learning. We did not find marked sex differences in either visual or verbal memory/learning measures, although some trend level effects were apparent and deserve exploration in future studies.

BIPOLAR DISORDER, MOOD STABILIZERS AND COGNITIVE FLEXIBILITY: TRANSLATIONALLY DISSECTING ILLNESS FROM DRUG EFFECTS

Bipolar disorder (BD) effects on cognition are confounded by the putative cognitive impact of its major pharmacological treatments, given the neurotrophic potential of mood stabilizers, particularly lithium. We examined the area of cognitive flexibility (CF), aiming to disentangle BD from medication effects, using translational methodology. CF was assessed by CANTAB-IED (intra- extra-dimensional shift; Study 1, euthymic BD participants) and its animal analogue (Study 2, rats). Both studies included groups (1) control, (2) lithium, chronic, current treatment (LI-CHRON-C, A: >2 years, N=32; B: 2 months, N=11); (3) valproate, chronic, current treatment (VPA-CHRON-C, A: >2 years, N=30; B: 2 months, N=12). Study 2 included 2 additional groups; Group 4: LI-CHRON-PAST (2 months, stopped 1 month pretest, N=13); Group 5: LI-ACUTE (LI on test days only, N=13). In Study 1, neither total nor stage (discrimination: D; reversal R; intra- extra-dimensional shifts: IED) IED errors differed between groups [(Kruskal-Wallis: H(2, N= 94) 0.95 > p > 0.65]. Similarly in Study 2, errors did not differentiate the 5 pharmacological groups. Differences emerged only between LI-ACUTE and Controls in response latencies (D, R, IED ANOVAS: 0.002 > p > 0.0003; contrasts D, R: p = 0.002, 0.0001). In conclusion, LI and VPA BD patients were indistinguishable from Controls in IED errors, as were animals treated with LI-CHRON, current or past, or VPA-CHRON-C vs Controls. LI-ACUTE treatment produced significant latency deficits vs. Controls. Within the limitations of translational comparisons, our results suggest that the normal CF noted in euthymic BDs is not attributable to mood stabilizer effects.

Cortisol to Dehydroepiandrosterone Sulphate Ratio and Executive Function in Bipolar Disorder

INTRODUCTION

Bipolar disorder (BD) is associated with impairment in cognitive domains such as verbal memory and executive functions. Very few studies have assessed dehydroepiandrosterone sulphate (DHEA-S) in BD and its relation to cognitive functioning despite evidence showing its regulatory effects on glucocorticoid action. The aim of our study was to explore the association of cortisol, DHEA-S, and cortisol to DHEA-S ratio with visuospatial memory and executive functioning in BD.

METHODS

Cognitive performance of 60 bipolar I patients and 30 healthy subjects was evaluated by using Cambridge Neuropsychological Test Automated Battery tasks targeting visuospatial memory (spatial recognition memory) and executive functions (planning [Stockings of Cambridge; SOC] and attentional set shifting [ID/ED]). Morning serum cortisol and DHEA-S levels were measured in patients. Main effects of cortisol, DHEA-S, and cortisol/DHEA-S ratio for each neurocognitive task were explored in multiple regression analyses correcting for demographic and clinical parameters as well as treatment-related factors (current use of antipsychotic and mood stabilizer medication).

RESULTS

Bipolar patients showed poorer performance than healthy subjects in planning and attentional set shifting but not in visuospatial memory. Cortisol to DHEA-S ratio predicted worse performance in planning (SOC).

CONCLUSIONS

This is the first study to assess memory and executive function in BD in relation to DHEA-S and cortisol to DHEA-S ratio. We report an association of cortisol to DHEA-S ratio with worse performance in planning in bipolar I patients, which warrants further investigation.

Differential association of cortisol with visual memory/learning and executive function in Bipolar Disorder

The association of cortisol with cognition has been understudied in Bipolar Disorder (BD); available evidence is inconsistent while it is unknown whether cortisol's effects vary across neurocognitive domains implicating different brain structures. This study aimed to examine the association of cortisol with two cognitive tasks targeting visual memory and executive function (planning) in BD, related to the hippocampus and prefrontal lobe, respectively. Cambridge Neuropsychological Test Automated Battery (CANTAB) tasks targeting paired associative learning (PAL) and planning (Stockings of Cambridge; SOC) were administered to 60 BD type I patients. Basal serum cortisol was also measured. Higher cortisol was associated with worse performance in PAL, but not SOC, after controlling for gender, education, illness duration and treatment with mood stabilizers. This is the first study to examine the association of cortisol with neurocognitive function in BD while controlling for clinicodemographic and treatment-related factors. We found a significant association of cortisol with hippocampal-related visual memory/learning but not with prefrontal lobe-related executive function, suggesting domain-specific underlying mechanisms of cognitive dysfunction in BD. Future studies should further explore cortisol's brain structure-specific effects on cognitive functioning in BD.

Similar or Different Neuropsychological Profiles? Only Set Shifting Differentiates Women With Bipolar vs. Borderline Personality Disorder

There is ongoing debate about the similarities and differences between bipolar disorder (BD) and borderline personality disorder (BPD). Very few studies have concurrently assessed their neuropsychological profile and only on a narrow array of neuropsychological tests. We aimed to investigate the differences of these two patient groups on visual memory, executive function, and response inhibition. Twenty-nine BD patients, 27 BPD patients and 22 controls (all female) were directly compared on paired associates learning (PAL), set shifting (ID/ED), problem solving (SOC), and response inhibition (SSRT) using Cambridge Neuropsychological Test Automated Battery (CANTAB). Rank-normalized outcomes were contrasted in one-way ANOVA tests. Discriminant analysis was finally performed to predict BD or BPD patient status. BD patients performed significantly worse than controls on all tasks. BPD patients performed significantly worse than HC on all tests except SST. Significant differences between the two patient groups were recorded only on ID/ED, where BPD patients performed worse (p = 0.044). A forward stepwise discriminant analysis model based on ID/ED and SOC predicted correctly patients' group at 67.9% of cases. In conclusion, BD and BPD female patients appear to be more similar than different as regards their neuropsychological functions. This study is the first to show that BPD patients display more deficits than BD patients when directly compared on the set shifting executive function test, a marker of cognitive flexibility. Discerning BD from BPD patients through neuropsychological performance is promising but would improve by using additional subtler tests and psychometric evaluation.

Executive functioning of older adults with bipolar disorder

OBJECTIVES

Despite their impact on daily functioning, we have limited understanding of the executive functioning of older adults with bipolar disorder (OABD). Even less is known about the possible differences in the executive functioning of OABD and older adults with unipolar depression (OADEP).

METHODS

After excluding acutely ill patients, the executive functioning of OABD was compared to that of OADEP and healthy controls (n = 22, n = 20, n = 22; respectively). Cognitive insight, a sub-domain of executive functioning, was operationalized as the discrepancy between the participants' self-reported cognitive functioning and appraisals that were made by their care partners. To complement the cognitive profiling, the groups were compared in information processing speed, verbal memory, and visual-spatial memory.

RESULTS

OABD were impaired in several cognitive domains compared to healthy controls, most prominently in executive functioning and memory. OABD had poorer executive functioning and visual-spatial memory than OADEP. The findings also tentatively point toward intact cognitive insight among OABD, while OADEP seem to have a heightened level of awareness of their cognitive impairment.

CONCLUSIONS

OABD have a unique profile of cognitive impairment compared to OADEP. It is characterized by a more severe cognitive impairment, accompanied by relatively intact cognitive insight. The findings may help clarify the cognitive profile of OABD and assist in the development of cognitive rehabilitation programs tailored to their needs. They should, however, be considered preliminary and await further research.

Relational memory in the early stage of psychotic bipolar disorder

Relational memory is impaired in psychotic disorders. In non-affective psychotic disorders, relational memory deficits are present in the early stage of illness and become more pronounced in the chronic stage. Previous studies have demonstrated cognitive deficits in early-stage psychotic bipolar disorder, but it is unclear whether relational memory is impaired. We examined relational memory using a face-scene binding task in early-stage psychotic bipolar disorder patients (n = 33) and compared their performance with healthy control (n = 40) and early-stage non-affective psychosis participants (n = 40). During training, participants learned to associate faces with background scenes. During testing, participants viewed a scene overlaid by three faces and were asked to recall the matching face. Relational memory was assessed indirectly using eye movements and explicitly using forced-choice recognition. Preferential viewing of the matching face, as captured by overall proportion of viewing and viewing across time, was significantly lower in psychotic bipolar disorder than in the healthy control group. However, preferential viewing of the matching face in psychotic bipolar disorder was significantly better than in non-affective psychosis. These findings provide novel evidence that relational memory in patients with early-stage psychotic bipolar disorder is intermediate between healthy control and early-stage non-affective psychosis subjects.

The Effect of DHA Supplementation on Cognition in Patients with Bipolar Disorder: An Exploratory Randomized Control Trial

Bipolar disorder (BD) is a severe mental disorder with a wide range of cognitive deficits, both in the euthymic and acute phase of the disease. Interestingly, in recent years, there has been a growing interest in investigating the impact of ω-3 polyunsaturated fatty acids on cognition in BD. In this context, the aim of this study is to evaluate the effect of docosahexaenoic acid (C22:6 ω-3, DHA) supplementation on cognitive performances in euthymic BD patients. This is an exploratory, single-centre, double-blind randomized controlled trial evaluating 12 weeks DHA supplementation (1250 mg daily) vs. a placebo (corn oil) in 31 euthymic BD patients compared to 15 healthy controls (HCs) on cognitive functions, assessed by the Brief Assessment of Cognition in Affective Disorder (BAC-A). Plasma levels of DHA were measured. After 12 weeks of treatment, no significant group differences were observed in all neuropsychological tests between the four groups, except for the emotion inhibition test, where HCs with DHA had higher scores compared to either BD with DHA (z = 3.9, p = 0.003) or BD with placebo (t = 3.7, p = 0.005). Although our results showed that DHA could be effective for ameliorating cognition in healthy subjects, future studies are still needed to clarify the impact of DHA on cognition in BD.

A focus on valproate and cognitive deficits in Bipolar Disorders: A mini-review: Special Section on "Translational and Neuroscience Studies in Affective Disorders" Section Editor, Maria Nobile MD, PhD

BACKGROUND

Cognitive deficits represent a core feature of Bipolar Disorder (BD), which seem to characterize this disorder regardless of the mood phase. However, the role of pharmacological treatment in determining cognitive alterations is still not clear. Indeed, although drugs improve cognition by targeting mood symptoms, they could also carry their own cognitive side effects. This is true especially for mood stabilizers as they are the most commonly prescribed drugs in patients affected by BD and they are usually administered also during euthymic phases.

METHODS

In this context, the present review aimed at summarizing the results of the studies evaluating the impact of valproate on cognitive functions in patients suffering from BD, as primary or secondary results. The inclusion criteria were met by ten studies. Specifically, we included one double-blind quasi-randomized study and nine cross-sectional or naturalistic studies, which a) used healthy subjects as control group (N = 1), b) compared valproate treated patients with healthy individuals and other treatments (N = 5), and c) compared valproate treated patients just with other treatments, with a specific focus on lithium (N = 3).

RESULTS

Overall the results suggested a negative effect of valproate on cognitive functions in chronically-treated patients affected by BD. Notably, it has been found that the working memory was the most affected cognitive domain.

LIMITATIONS

Few studies directly explored the effect of valproate on cognition in BD.

CONCLUSIONS

These findings seem to suggest that valproate might have a negative effect on cognitive functions, especially on working memory domain. However, the results should be taken cautiously since the limited number of available studies published so far. In conclusion, these evidences seem to point out that the possible cognitive side effects of pharmacological treatments should be carefully taken into account, especially in chronic patients.

Cognitive Impairment in Patients with Bipolar Disorder: Impact of Pharmacological Treatment

Bipolar disorder is an illness characterised by periods of elated and depressed mood. These mood episodes are associated with changes in cognitive function and there is evidence to suggest that cognitive dysfunction persists during euthymia. The extent to which this is a function of the illness or a result of treatment is less clear. In this narrative review, we explore the impact of commonly used medications for bipolar disorder on cognitive function. Specific impairments in executive function and verbal memory have been noted in bipolar disorder. The impact of pharmacological treatments upon cognitive function is mixed with a number of studies reporting conflicting results. Interpretation of the data is further complicated by the variety of cognitive tests employed, study design, the relatively small numbers of patients included and confounding by indication. Overall, there is some evidence that while lithium improves some cognitive domains, it impedes others. Antipsychotics may be deleterious to cognition, although this may relate to the patient population in which they are prescribed. Sodium valproate is also associated with worse cognitive outcomes, while the impact of other antiepileptics is unclear. Overall the quality of evidence is poor and is derived from a relatively small number of studies that often do not account for the significant heterogeneity of the disorder or common comorbidities. The use of consistent methodologies and measures of cognition across studies, as well as in naturalistic settings, would enable more certain conclusions to be drawn.

Neuroanatomical Dysconnectivity Underlying Cognitive Deficits in Bipolar Disorder

BACKGROUND

Graph theory applied to brain networks is an emerging approach to understanding the brain's topological associations with human cognitive ability. Despite well-documented cognitive impairments in bipolar disorder (BD) and recent reports of altered anatomical network organization, the association between connectivity and cognitive impairments in BD remains unclear.

METHODS

We examined the role of anatomical network connectivity derived from T1- and diffusion-weighted magnetic resonance imaging in impaired cognitive performance in individuals with BD (n = 32) compared with healthy control individuals (n = 38). Fractional anisotropy- and number of streamlines-weighted anatomical brain networks were generated by mapping constrained spherical deconvolution-reconstructed white matter among 86 cortical/subcortical bilateral brain regions delineated in the individual's own coordinate space. Intelligence and executive function were investigated as distributed functions using measures of global, rich-club, and interhemispheric connectivity, while memory and social cognition were examined in relation to subnetwork connectivity.

RESULTS

Lower executive functioning related to higher global clustering coefficient in participants with BD, and lower IQ performance may present with a differential relationship between global and interhemispheric efficiency in individuals with BD relative to control individuals. Spatial recognition memory accuracy and response times were similar between diagnostic groups and associated with basal ganglia and thalamus interconnectivity and connectivity within extended anatomical subnetworks in all participants. No anatomical subnetworks related to episodic memory, short-term memory, or social cognition generally or differently in BD.

CONCLUSIONS

Results demonstrate selective influence of subnetwork patterns of connectivity in underlying cognitive performance generally and abnormal global topology underlying discrete cognitive impairments in BD.

Sex-related variation of neurocognitive functioning in bipolar disorder: Focus on visual memory and associative learning

Bipolar disorder (BD) is associated with cognitive deficits in attention, verbal memory and executive functions. However, only few studies have examined sex effects on cognition despite their clinical relevance. Given that visual memory/ learning has been understudied the aim of our study was to investigate sex-related variation in cognition (executive functions and visual memory/ learning) in BD. Cognitive performance of 60 bipolar-I patients and 30 healthy controls was evaluated by using CANTAB battery tasks targeting spatial memory (SRM), paired associative learning (PAL) and executive functions. We fitted a multivariate analysis of covariance (MANCOVA), followed by task-specific ANCOVAs. A significant diagnosis by sex interaction effect was detected (MANCOVA); specifically, diagnosis-specific sex effects were found for SRM and PAL, as healthy males outperformed healthy females but this pattern was attenuated in BD patients. Patients' clinicodemographic characteristics, current psychopathology or medication status did not differ across sexes and were, therefore, unlikely to explain detected sex effects. Our study is one of few studies to assess sex-related variation in cognition in BD and the first to record a diagnosis-specific sex effect for two tasks of visuo-spatial memory/ learning, indicating that sex-related variation in healthy subjects is disrupted in BD.