Response inhibition and interference control in patients with bipolar I disorder and first-degree relatives

Diagnostic value of regional homogeneity and fractional amplitude of low-frequency fluctuations in the classification of schizophrenia and bipolar disorders

Schizophrenia (SCZ) and bipolar disorders (BD) show significant neurobiological and clinical overlap. In this study, we wanted to identify indexes of intrinsic brain activity that could differentiate these disorders. We compared the diagnostic value of the fractional amplitude of low-frequency fluctuations (fALFF) and regional homogeneity (ReHo) estimated from resting-state functional magnetic resonance imaging in a support vector machine classification of 59 healthy controls (HC), 40 individuals with SCZ, and 43 individuals with BD type I. The best performance, measured by balanced accuracy (BAC) for binary classification relative to HC was achieved by a stacking model (87.4% and 90.6% for SCZ and BD, respectively), with ReHo performing better than fALFF, both in SCZ (86.2% vs. 79.4%) and BD (89.9% vs. 76.9%). BD were better differentiated from HC by fronto-temporal ReHo and striato-temporo-thalamic fALFF. SCZ were better classified from HC using fronto-temporal-cerebellar ReHo and insulo-tempo-parietal-cerebellar fALFF. In conclusion, we provided evidence of widespread aberrancies of spontaneous activity and local connectivity in SCZ and BD, demonstrating that ReHo features exhibited superior discriminatory power compared to fALFF and achieved higher classification accuracies. Our results support the complementarity of these measures in the classification of SCZ and BD and suggest the potential for multivariate integration to improve diagnostic precision.

Impulsivity and neural correlates of response inhibition in bipolar disorder and their unaffected relatives: A MEG study

BACKGROUND

Response inhibition is a core cognitive impairment in bipolar disorder (BD), leading to increased impulsivity in BD. However, the relationship between the neural mechanisms underlying impaired response inhibition and impulsivity in BD is not yet clear. Individuals who are genetically predisposed to BD give a way of identifying potential endophenotypes.

METHODS

A total of 97 participants, including 39 patients with BD, 22 unaffected relatives (UR) of patients with BD, and 36 healthy controls performed a Go/No-Go task during magnetoencephalography. We carried out time-frequency and connectivity analysis on MEG data.

RESULTS

Decreased beta power, prolonged latency and increased peak frequency in rIFG, decreased beta power in pre-SMA and reduced rIFG-to-pre-SMA connectivity were found in BD relative to healthy controls. In the UR group, we found a decrease in the beta power of pre-SMA and prolonged latency of rIFG. Furthermore, increased motor impulsiveness in BD was related to abnormal alterations in beta oscillatory activity of rIFG and functional connectivity between rIFG and pre-SMA.

CONCLUSIONS

Hypoactivity activity in rIFG and impaired dominant role of rIFG in the prefrontal control network may underlie the neuropathology of response inhibition dysfunction, resulting increased motor impulsivity in BD. Our findings point to measuring rIFG dysfunction as a potential means of identifying individuals at genetic high risk for transition to BD disease expression.

Response inhibition related neural oscillatory patterns show reliable early identification of bipolar from unipolar depression in a Go/No-Go task

BACKGROUND

Response inhibition is a key neurocognitive factor contributing to impulsivity in mood disorders. Here, we explored the common and differential alterations of neural circuits associated with response inhibition in bipolar disorder (BD) and unipolar disorder (UD) and whether the oscillatory signatures can be used as early biomarkers in BD.

METHODS

39 patients with BD, 36 patients with UD, 29 patients initially diagnosed with UD who later underwent diagnostic conversion to BD, and 36 healthy controls performed a Go/No-Go task during MEG scanning. We carried out time-frequency and connectivity analysis on MEG data. Further, we performed machine learning using oscillatory features as input to identify bipolar from unipolar depression at the early clinical stage.

RESULTS

Compared to healthy controls, patients had reduced rIFG-to-pre-SMA connectivity and delayed activity of rIFG. Among patients, lower beta power and higher peak frequency were observed in BD patients than in UD patients. These changes enabled accurate classification between BD and UD with an accuracy of approximately 80 %.

CONCLUSIONS

The inefficiency of the prefrontal control network is a shared mechanism in mood disorders, while the abnormal activity of rIFG is more specific to BD. Neuronal responses during response inhibition could serve as a diagnostic biomarker for BD in early stage.

Intra- and inter-individual cognitive variability in schizophrenia and bipolar spectrum disorder: an investigation across multiple cognitive domains

There is substantial cognitive heterogeneity among patients with schizophrenia (SZ) and bipolar disorders (BD). More knowledge about the magnitude and clinical correlates of performance variability could improve our understanding of cognitive impairments. Using double generalized linear models (DGLMs) we investigated cognitive mean and variability differences between patients with SZ (n = 905) and BD spectrum disorders (n = 522), and healthy controls (HC, n = 1170) on twenty-two variables. The analysis revealed significant case-control differences on 90% of the variables. Compared to HC, patients showed larger intra-individual (within subject) variability across tests and larger inter-individual (between subject) variability in measures of fine-motor speed, mental processing speed, and inhibitory control (SZ and BD), and in verbal learning and memory and intellectual functioning (SZ). In SZ, we found that lager intra -and inter (on inhibitory control and speed functions) individual variability, was associated with lower functioning and more negative symptoms. Inter-individual variability on single measures of memory and intellectual function was additionally associated with disorganized and positive symptoms, and use of antidepressants. In BD, there were no within-subject associations with symptom severity. However, greater inter-individual variability (primarily on inhibitory control and speeded functions) was associated with lower functioning, more negative -and disorganized symptoms, earlier age at onset, longer duration of illness, and increased medication use. These results highlight larger individual differences in patients compared to controls on various cognitive domains. Further investigations of the causes and correlates of individual differences in cognitive function are warranted.

Antidepressant-induced mania in panic disorder: a single-case study of clinical and functional connectivity characteristics

Background

Mental health issues, including panic disorder (PD), are prevalent and often co-occur with anxiety and bipolar disorders. While panic disorder is characterized by unexpected panic attacks, and its treatment often involves antidepressants, there is a 20-40% risk of inducing mania (antidepressant-induced mania) during treatment, making it crucial to understand mania risk factors. However, research on clinical and neurological characteristics of patients with anxiety disorders who develop mania is limited.

Methods

In this single case study, we conducted a larger prospective study on panic disorder, comparing baseline data between one patient who developed mania (PD-manic) and others who did not (PD-NM group). We enrolled 27 patients with panic disorder and 30 healthy controls (HCs) and examined alterations in amygdala-based brain connectivity using a seed-based whole-brain approach. We also performed exploratory comparisons with healthy controls using ROI-to-ROI analyses and conducted statistical inferences at a threshold of cluster-level family-wise error-corrected p < 0.05, with the cluster-forming threshold at the voxel level of uncorrected p < 0.001.

Results

The patient with PD-mania showed lower connectivity in brain regions related to the default mode network (left precuneous cortex, maximum z-value within the cluster = -6.99) and frontoparietal network (right middle frontal gyrus, maximum z-value within the cluster = -7.38; two regions in left supramarginal gyrus, maximum z-value within the cluster = -5.02 and -5.86), and higher in brain regions associated with visual processing network (right lingual gyrus, maximum z-value within the cluster = 7.86; right lateral occipital cortex, maximum z-value within the cluster = 8.09; right medial temporal gyrus, maximum z-value within the cluster = 8.16) in the patient with PD-mania compared to the PD-NM group. One significantly identified cluster, the left medial temporal gyrus (maximum z-value within the cluster = 5.82), presented higher resting-state functional connectivity with the right amygdala. Additionally, ROI-to-ROI analysis revealed that significant clusters between PD-manic and PD-NM groups differed from HCs in the PD-manic group but not in the PD-NM group.

Conclusion

Here, we demonstrate altered amygdala-DMN and amygdala-FPN connectivity in the PD-manic patient, as reported in bipolar disorder (hypo) manic episodes. Our study suggests that amygdala-based resting-state functional connectivity could serve as a potential biomarker for antidepressant-induced mania in panic disorder patients. Our findings provide an advance in understanding the neurological basis of antidepressant-induced mania, but further research with larger cohorts and more cases is necessary for a broader perspective on this issue.

MICEmi: A method to identify cognitive endophenotypes of mental illnesses

BACKGROUND

Characterizing neurocognitive endophenotypes of mental illnesses (MIs) could be useful for identifying at-risk individuals, increasing early diagnosis, improving disease subtyping, and proposing therapeutic strategies to reduce the negative effects of the symptoms, in addition to serving as a scientific basis to unravel the physiopathology of the disease. However, a standardized algorithm to determine cognitive endophenotypes has not yet been developed. The main objective of this study was to present a method for the identification of endophenotypes in MI research.

METHODS

For this purpose, a 14-expert working group used a scoping review methodology and designed a method that includes a scoring template with five criteria and indicators, a strategy for their verification, and a decision tree.

CONCLUSIONS

This work is ongoing since it is necessary to obtain external validation of the applicability of the method in future research.

Effects of Exercise on Neural Changes in Inhibitory Control: An ALE Meta-Analysis of fMRI Studies

It is widely known that exercise improves inhibitory control; however, the mechanisms behind the cognitive improvement remain unclear. This study analyzes the extant literature on the neuronal effects of exercise on inhibitory control functions. We searched four online databases (Pubmed, Scopus, PsycINFO, and Web of Science) for relevant peer-reviewed studies to identify eligible studies published before September 1, 2021. Among the 4,090 candidate studies identified, 14 meet the inclusion criteria, and the results of 397 participants in these 14 studies are subsequently analyzed. We quantify the neural effects on the entire brain by using GingerALE software and identify 10 clusters of exercise-induced neuronal with either increases/decreases in the superior temporal gyrus (BA 22), precuneus (BA 7), superior frontal gyrus (BA 10), cuneus (BA 19), precuneus (BA 19), caudate, posterior cingulate (BA 19), middle temporal gyrus (B 37), parahippocampal gyrus (BA 30), precentral gyrus (BA 6). Meta-analytic coactivation map (MACM) showed that multiple functional networks overlap with brain regions with activation likelihood estimation (ALE) results. We propose the effect of exercise on neural activity is related to inhibitory control in the extended frontoparietal, default mode network (DMN), visual network, and other pathways. These results provide preliminary evidence of the neural effects of exercise on inhibitory control.

Visual Event-Related Potentials under External Emotional Stimuli in Bipolar I Disorder with and without Hypersexuality

Hypersexuality is related to functions of personality and emotion and is a salient symptom of bipolar I disorder especially during manic episode. However, it is uncertain whether bipolar I disorder with (BW) and without (BO) hypersexuality exhibits different cerebral activations under external emotion stimuli. In 54 healthy volunteers, 27 BW and 26 BO patients, we administered the visual oddball event-related potentials (ERPs) under external emotions of Disgust, Erotica, Fear, Happiness, Neutral, and Sadness. Participants’ concurrent states of mania, hypomania, and depression were also evaluated. The N1 latencies under Erotica and Happiness were prolonged, and the P3b amplitudes under Fear and Sadness were decreased in BW; the P3b amplitudes under Fear were increased in BO. The parietal, frontal, and occipital activations were found in BW, and the frontal and temporal activations in BO under different external emotional stimuli, respectively. Some ERP components were correlated with the concurrent affective states in three groups of participants. The primary perception under Erotica and Happiness, and voluntary attention under Fear and Sadness, were impaired in BW, while the voluntary attention under Fear was impaired in BO. Our study indicates different patterns of visual attentional deficits under different external emotions in BW and BO.

Effect of medication therapy combined with transcranial direct current stimulation on depression and response inhibition of patients with bipolar disorder type I: a clinical trial

OBJECTIVE

Bipolar Disorder (BD) is one of the most common mental disorders associated with depressive symptoms and impairment in executive functions such as response inhibition. This study aimed to investigate the effectiveness of medication therapy combined with Transcranial Direct Current Stimulation (tDCS) on depression and response inhibition of patients with BD.

METHOD

This is a double-blinded randomized clinical trial with pretest, posttest, and follow-up design. Participants were 30 patients with BD randomly assigned to two groups of Medication+tDCS (n = 15, receiving medications plus tDCS with 2 mA intensity over dorsolateral prefrontal cortex for 10 days, two sessions per day each for 20 min) and Medication (n = 15, receiving mood stabilizers including 2-5 tables of 300 mg (mg) lithium, 200 mg sodium valproate, and 200 mg carbamazepine two times per day). Pretest, posttest and 3-month follow-up assessments were the 21-item Hamilton Depression Rating Scale (HDRS) and a Go/No-Go test. Collected data were analyzed in SPSS v.20 software.

RESULTS

The mean HDRS score in both groups was reduced after both interventional techniques, where the group received combined therapy showed more reduction (P < 0.01), although their effects were not maintained after 3 months. In examining response inhibition variable, only the combined therapy could reduce the commission error of patients under a go/no-go task (p < 0.05), but its effect was not maintained after 3 months. There was no significant difference in the group received medication therapy alone.

CONCLUSION

Medication in combination with tDCS can reduce the depressive symptoms and improve the response inhibition ability of people with BD.

TRIAL REGISTRATION

This study was registred by Iranian Registry of Clinical Trials (Parallel, ID: IRCT20191229045931N1 , Registration date: 24/08/2020).

Frozen in (e)motion: How reactive motor inhibition is influenced by the emotional content of stimuli in healthy and psychiatric populations

Efficient inhibitory control is vital. However, environmental cues can influence motor control especially in an emotional context. One common task to measure inhibitory control is the stop-signal task (SST), which asks participants to respond to go stimuli knowing that on some trials a stop signal will be presented, requiring them to inhibit their response. This paradigm estimates the ability to inhibit already-initiated responses by calculating participants' stop-signal reaction times (SSRT), an index of inhibitory control. Here, we aim to review the existing, often contradictory, evidence on the influence of emotional stimuli on the inhibitory process. We aim to discuss which factors may reveal an interference as well as an advantage of emotional stimuli on action inhibition performance. Finally, we review the existing evidence that has investigated the effect of such stimuli on action inhibition in the psychiatric population. Important factors are the relevance, the intensity and the valence of the emotional stimulus, as well as the affected component of the motor control. From all this evidence, it is clear that understand precisely how emotion is integrated into core executive functions, such as inhibitory control, is essential not only for cognitive neuroscience, but also for refining neurocognitive models of psychopathology.

Familial aggregation analysis of cognitive performance in early-onset bipolar disorder

We analysed the familial aggregation (familiality) of cognitive dimensions and explored their role as liability markers for early-onset bipolar disorder (EOBD). The sample comprised 99 subjects from 26 families, each with an offspring diagnosed with EOBD. Four cognitive dimensions were assessed: reasoning skills; attention and working memory; memory; and executive functions. Their familiality was investigated in the total sample and in a subset of healthy relatives. The intra-family resemblance score (IRS), a family-based index of the similarity of cognitive performance among family members, was calculated. Familiality was detected for the attention and working memory (AW) dimension in the total sample (ICC = 0.37, p = 0.0004) and in the subsample of healthy relatives (ICC = 0.37, p = 0.016). The IRS reflected that there are families with similar AW mean scores (either high or low) and families with heterogeneous scores. Families with the most common background for the AW dimension (IRS > 0) were selected and dichotomized in two groups according to the mean family AW score. This allowed differentiating families whose members had similar high scores than those with similar low scores: both patients (t = - 4.82, p = 0.0005) and relatives (t = - 5.04, p < 0.0001) of the two groups differed in their AW scores. AW dimension showed familial aggregation, suggesting its putative role as a familial vulnerability marker for EOBD. The IRS estimation allowed the identification of families with homogeneous scores for this dimension. This represents a first step towards the investigation of the underlying mechanisms of AW dimension and the identification of etiological subgroups.

Distinguishing patterns of impairment on inhibitory control and general cognitive ability among bipolar with and without psychosis, schizophrenia, and schizoaffective disorder

BACKGROUND

Deficits in inhibitory control on a Stop Signal Task (SST) were previously observed to be of similar magnitude across schizophrenia, schizoaffective, and bipolar disorder with psychosis, despite variation in general cognitive ability. Understanding different patterns of performance on the SST may elucidate different pathways to the impaired inhibitory control each group displayed. Comparing nonpsychotic bipolar disorder to the psychosis groups on SST may also expand our understanding of the shared neurobiology of this illness spectrum.

METHODS

We tested schizophrenia (n = 220), schizoaffective (n = 216), bipolar disorder with (n = 192) and without psychosis (n = 67), and 280 healthy comparison participants with a SST and the Brief Assessment of Cognition in Schizophrenia (BACS), a measure of general cognitive ability.

RESULTS

All patient groups had a similar degree of impaired inhibitory control over prepotent responses. However, bipolar groups differed from schizophrenia and schizoaffective groups in showing speeded responses and inhibition errors that were not accounted for by general cognitive ability. Schizophrenia and schizoaffective groups had a broader set of deficits on inhibition and greater general cognitive deficit, which fully accounted for the inhibition deficits. No differences were found between the clinically well-matched bipolar with and without psychosis groups, including for inhibitory control or general cognitive ability.

CONCLUSIONS

We conclude that 1) while impaired inhibitory control on a SST is of similar magnitude across the schizo-bipolar spectrum, including nonpsychotic bipolar, different mechanisms may underlie the impairments, and 2) history of psychosis in bipolar disorder does not differentially impact inhibitory behavioral control or general cognitive abilities.

A comparative meta-analysis of neurocognition in first-degree relatives of patients with schizophrenia and bipolar disorder

Objective:

Cognitive impairment is a familial and heritable aspect of major psychoses and might be a shared vulnerability marker for schizophrenia and BP. However, it is not clear whether some aspects of cognitive deficits are uniquely associated with risk for specific diagnoses.

Methods:

A novel meta-analysis of cognitive functions in first-degree relatives of probands with bipolar disorder (BP-Rel) and schizophrenia (Sch-Rel) was conducted. Current meta-analysis included 20 studies and compared cognitive functions of 1341 Sch-Rel, 939 BP-Rel and 1427 healthy controls.

Results:

Sch-Rel was associated with cognitive deficits in all domains (d = 0.20–0.58) and BP-Rel underperformed healthy controls in processing speed, verbal fluency and speed based executive function tests (d = 0.33–0.41). Sch-Rel underperformed BP-Rel in general intellectual ability, working memory, verbal memory, planning, processing speed and fluency (d = 0.24–0.42).

Conclusions:

Inefficiency in processing information and impaired processing speed might be common vulnerability factors for major psychoses. On the other hand, low performance in accuracy based tasks and deficits in general intellectual ability, verbal learning, planning and working memory might be more specifically associated with risk for schizophrenia.

A meta-analysis of neurocognition in youth with familial high risk for bipolar disorder

Objective:

Neuropsychological impairment, including deficits in social cognition is evident in subjects at genetic high-risk for psychosis. However, findings in youth at genetic risk to bipolar disorder (BP) have been suggested to be less supportive of premorbid deficits. We aimed to conduct a meta-analysis of cognitive deficits in youth with familiar risk for bipolar disorder (FHR-BD).

Methods:

A novel meta-analysis of FHR-BD (mean age 10–25), including 18 studies (786 offsprings/siblings of patients with BD and 794 healthy controls), was conducted.

Results:

Both general cognition (d = 0.29, CI = 0.15–0.44) and social cognition (d = 0.23, CI = 0–0.45) were impaired in FHR-BD. In comparison to controls, FHR-BD had significant deficits in several cognitive domains, including visual memory (d = 0.35), verbal memory (d = 0.21), processing speed (d = 0.26) and sustained attention (d = 0.36). There was no significant difference between FHR-BD and controls in planning and working memory.

Conclusions:

Cognitive deficits are evident in individuals who are at genetic high-risk for developing BD. Neurodevelopmental abnormalities are likely playing a role not only in schizophrenia but also in BD.

Neurocognition in young offspring of individuals with bipolar disorder: The role of co-existing familial and clinical high-risk for bipolar disorder

Bipolar disorder (BD) is associated with cognitive dysfunction which has also been reported in offspring of individuals with BD (BDoff). However, it remains unclear whether cognitive underperformance in BDoff is associated with the presence of history of subclinical syndromes associated with risk for BD. To address this knowledge gap we assessed executive function, visual and verbal memory, working memory, processing speed and verbal fluency in 21 offspring with clinical high risk (CHR; BDoff+CHR), 54 offspring without CHR (BDoff-non-CHR), and 50 healthy individuals without familial risk of BD. BDoff underperformed compared to controls in most cognitive tasks. There was no significant neurocognitive difference between BDoff+CHR and BDoff-non-CHR except in the fluency/central executive domain (Cohen's d = 0.60, p = 0.03). Our results suggest that cognitive dysfunction in multiple domains is associated with familial predisposition to BD regardless of CHR status. On the other hand, abnormalities in central executive processes might be more pronounced in BDoff+CHR than BDoff-non-CHR. Further longitudinal studies investigating cognitive trajectory of BDoff and its interaction with the emergence of subclinical syndromes are needed to fully characterize the relationship between cognition and mood dysregulation in BD.

Semantic Ambiguity Resolution in Patients With Bipolar Disorder-An Event-Related Potential Study

Deficits in inhibitory function are assumed to underlie psychopathology in bipolar disorder (BD), especially in states of mania. A subdomain of inhibition, semantic inhibition (SI), referring to the suppression of irrelevant word meanings, may underlie formal thought disorder, such as flights of ideas. In the present study, we investigated SI in patients with BD during semantic ambiguity resolution using behavioral and event-related potential (ERP) measures. We presented 14 patients with BD with current manic, hypomanic, or mixed clinical states and 28 healthy controls sequentially with word triplets containing either a homonym (e.g., “organ”) or a comparable unambiguous word (e.g., “piano”). Participants were instructed to make a decision whether or not the target word was related to the meaning field of the first two words. The inappropriate homonym meaning had to be inhibited to correctly perform the target decision. In addition to reaction times (RT) and error rates (ER), the N400 ERP component to the target, an electrophysiological index of semantic processing, was analyzed as measure of the amount of SI that had taken place. Analyses of the behavioral data revealed that BD patients exhibited an overall worse performance in terms of RT and ER. In the ERP data, we found differences in N400 amplitude to ambiguous and unambiguous conditions over the right hemisphere in patients with BD depending on target congruence: In incongruent trials, N400 amplitude was smaller in ambiguous than in unambiguous words. In congruent trials, in contrast, N400 amplitude was larger in ambiguous than in unambiguous words. Such ERP differences between ambiguous and unambiguous words were absent in controls. We conclude that N400 amplitude differences in the ambiguous and unambiguous conditions of the BD group may reflect insufficient suppression of irrelevant homonym meanings in the right hemisphere. Disturbed SI processes might contribute to formal thought disorder in BD.

Impaired cognitive control over emotional material in euthymic bipolar disorder

BACKGROUND

Previous research suggests that bipolar disorder (BD) is characterized by deficits in cognitive control (CC). Impaired CC has been found in high-risk samples and is associated with the maintenance of BD symptoms. It remains unclear, however, whether BD is characterized by a general deficit in CC or by a deficit that is specifically related to the processing of emotional material.

METHODS

The sample consisted of 42 remitted bipolar patients and 39 healthy controls (HC). We examined whether BD individuals display impaired CC when confronted with negative as well as positive material using an arithmetic inhibition task that required inhibition of pictorial stimulus material.

RESULTS

Whereas both groups showed difficulties in exerting CC over negative material, only BD individuals exhibited deficient CC over positive material.

LIMITATIONS

Even though we intended the negative and positive pictures in the arithmetic inhibition task to be similarly arousing, participants in the current study rated the negative compared to the positive pictures as more arousing.

CONCLUSIONS

BD is associated with impaired CC when processing emotional - especially positive - stimuli even when patients are in remission. Possible implications of this deficit especially for emotion regulation are discussed.

Social cognition in first-degree relatives of patients with bipolar disorder: A meta-analysis

Cognitive impairment is evident euthymic patients with bipolar disorder (BP) and in their first-degree relatives (BP-Rel). Increasing evidence suggests that BP is also associated with social cognitive impairment. It is important to establish whether social cognitive impairment is also evident in BP-Rel. A novel meta-analysis of theory of mind (ToM) and facial emotion recognition in BP-Rel including 16 studies (728 first-degree relatives of patients with BP and 865 healthy controls) was conducted. ToM (d=0.34, CI=0.16-0.52) was significantly impaired in BP-Rel. The effect size for the difference between BP-Rel and healthy controls was smaller for facial emotion recognition (d=0.17, CI=0.16-0.29) and could be nonsignificant after the effect of publication bias was taken into account. First-degree relatives of patients with BP underperform healthy subjects in social cognitive abilities, particularly in ToM. However, the effect size for between-group difference is small. ToM impairment might be a vulnerability marker of BP.

Emotion processing and psychosocial functioning in euthymic bipolar disorder

OBJECTIVE

To examine emotion processing in euthymic bipolar patients (EBP) compared to healthy controls. In addition, to determine whether or not there is an association between emotion processing and psychosocial functioning.

MATERIAL AND METHODS

A sample of 60 EBP and 60 healthy controls matched for age, gender, education level, and premorbid intelligence were studied. All subjects were assessed using the MATRICS Consensus Cognitive Battery (MCCB) and two additional executive function measures: the Trail Making Test-Part B and the Stroop Test. Emotion processing was examined using the Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT). Psychosocial functioning was assessed using the Functional Assessment Short Test (FAST).

RESULTS

Euthymic bipolar patients obtained lower scores than controls in all MSCEIT measures except for the using emotions branch. Likewise, EBP obtained a worse performance than healthy controls in all neurocognitive domains. Correlation between MSCEIT strategic area measures and FAST total score was found (r = -0.311; P < 0.016). Regression analysis showed that residual depressive symptomatology explains a 9.1% of the variance in functional outcome. MSCEIT strategic area score explained an additional 8.6%. Neurocognition did not increase the percentage of the variance explained by emotion processing.

CONCLUSIONS

Euthymic bipolar patients exhibit deficits in emotion processing. Emotion processing is associated with social functioning in these patients.

Neurobiology of Risk for Bipolar Disorder

Bipolar disorder (BD) is a chronic mental illness which follows a relapsing and remitting course and requires lifetime treatment. The lack of biological markers for BD is a major difficulty in clinical practice. Exploring multiple endophenotypes to fit in multivariate genetic models for BD is an important element in the process of finding tools to facilitate early diagnosis, early intervention, prevention of new episodes, and follow-up of treatment response in BD. Reviewing of studies on neuroimaging, neurocognition, and biochemical parameters in populations with high genetic risk for the illness can yield an integrative perspective on the neurobiology of risk for BD. The most up-to-date data reveals consistent deficits in executive function, response inhibition, verbal memory/learning, verbal fluency, and processing speed in risk groups for BD. Functional magnetic resonance imaging (fMRI) studies report alterations in the activity of the inferior frontal gyrus, medial prefrontal cortex, and limbic areas, particularly in the amygdala in unaffected first-degree relatives (FDR) of BD compared to healthy controls. Risk groups for BD also present altered immune and neurochemical modulation. Despite inconsistencies, accumulating data reveals cognitive and imaging markers for risk and to a less extent resilience of BD. Findings on neural modulation markers are preliminary and require further studies. Although the knowledge on the neurobiology of risk for BD has been inadequate to provide benefits for clinical practice, further studies on structural and functional changes in the brain, neurocognitive functioning, and neurochemical modulation have a potential to reveal biomarkers for risk and resilience for BD. Multimodal, multicenter, population-based studies with large sample size allowing for homogeneous subgroup analyses will immensely contribute to the elucidation of biological markers for risk for BD in an integrative model.

Executive dysfunction and cognitive subgroups in a large sample of euthymic patients with bipolar disorder

Bipolar disorder (BP), at the group level, is associated with significant but modest cognitive deficits, including executive dysfunction. Among executive functions, response inhibition deficits have been suggested to be particularly relevant to BP. However, BP is associated with significant heterogeneity in neurocognitive performance and level of functioning. Very few studies have investigated neurocognitive subgroups in BP with data-driven methods rather than arbitrarily defined criteria. Other than having relatively small sample sizes, previous studies have not taken into consideration the neurocognitive variability in healthy subjects. Five-hundred-fifty-six euthymic patients with BP and 416 healthy controls were assessed using a battery of cognitive tests and clinical measures. Neurocognitive subgroups were investigated using latent class analysis, based on executive functions. Four neurocognitive subgroups, including a good performance cluster, two moderately low-performance groups, which differ in response inhibition and reasoning abilities, and a severe impairment cluster were found. In comparison to healthy controls, BP patients were overrepresented in severe impairment cluster (27% vs 5.3%) and underrepresented in good performance cluster. BP patients with lower educational attainment and older age were significantly more likely to be members of cognitively impaired subgroups. Antipsychotic use was less common in good performance cluster. These results suggest that there is a considerable overlap of cognitive functions between BP and healthy controls. Neurocognitive differences between BP and healthy controls are driven by a subgroup of patients who have severe and global, rather than selective, cognitive deficits.

Executive Functions in Tobacco Dependence: Importance of Inhibitory Capacities

BACKGROUND

Executive functions are linked to tobacco dependence and craving. In this cross-sectional study, we assessed the impact of three executive functions: updating, inhibition and shifting processes on tobacco craving and dependence.

METHOD

134 tobacco consumers were included in this study: 81 moderately (Fagerström score <7) and 53 heavily dependent (Fagerström score >7). Dependence was assessed with the Fagerström test and craving with the tobacco craving questionnaire (TCQ 12). We used the Stroop test and the Hayling test to measure inhibition, the Trail Making Test to measure shifting processes and the n-back test to measure updating processes. A multivariate logistic model was used to assess which variables explained best the level of nicotine dependence.

RESULTS

Inhibition (p = 0.002) and updating (p = 0.014) processes, but not shifting processes, were associated with higher tobacco dependence. Inhibition capacity had a significant effect on the nicotine dependence level independently of age, education, time since last cigarette, intellectual quotient, craving, updating and shifting process.

CONCLUSIONS

Nicotine dependence level seems better explained by inhibition capacities than by craving and updating effects. The capacity to inhibit our behaviours is a good predictor of the severity of tobacco dependence. Our results suggest a prefrontal cortex dysfunction affecting the inhibitory capacities of heavy tobacco dependent smokers. Further studies are needed to investigate the application of these findings in the treatment of tobacco dependence.