Attentional networks in euthymic patients with unipolar depression

Measuring the attention networks and quantitative-electroencephalography correlates of attention in depression

Given the association between major depressive disorder (MDD) and cortical inefficiency related to executive control, specifically in the sense that individuals with MDD may recruit more cognitive resources to complete tasks at the same capacity as those without MDD, the current study was interested in examining the attention networks and executive functioning of those with MDD. Past research has used the Attention Network Test (ANT) to measure changes of attention in clinical vs. healthy populations; however, theoretical concerns have been raised regarding the task. The Combined Attention Systems Task (CAST) was developed to address these concerns and was used in our study in combination with quantitative-electroencephalography (QEEG) to assess both behavioural and neurophysiological changes in participants with MDD (n = 18) compared to healthy controls (HCs; n = 22). We found no behavioural differences between MDD and HC groups suggesting individuals with MDD in our sample were not experiencing the executive functioning deficits previously reported in the literature. Neurophysiological measures of attention revealed that MDD participants had greater theta and alpha₁ activity relative to HCs, suggesting that although individuals with MDD do not show deficits in behavioural attention, they exhibit altered neural processing which underlies cognitive function.

Executive control dysfunction in subclinical depressive undergraduates: Evidence from the Attention Network Test

BACKGROUND

It has been proposed that depressed individuals have broad neuropsychological dysfunction, particularly in the executive control domain. The Attention Network Test (ANT) is widely used to assess the efficiency of three attention networks: alerting, orienting, and executive control. In the present study, we investigated the behavioral and event-related potential (ERP) indicators of attention processing in subclinical depressive undergraduates.

METHODS

Seventeen undergraduates with subclinical depressive symptoms and sixteen control undergraduates completed the Attention Network Test (ANT).

RESULTS

The results indicated no difference in behavioral performance on the three attention networks between the two groups; and there was a similar ERP pattern in the ERP components involved in alerting and orienting (cue-N1 and target-N1) in both groups. Additionally, for executive function network, no difference in the N2 component associated with conflict detection was observed between the two groups. However, there was an increase in the congruency effect of the conflict-sustained potential (SP; incongruent minus congruent) related to conflict resolution in undergraduates with subclinical depressive symptoms compared with control undergraduates.

LIMITATIONS

The present study is limited by its small sample size which might result in inadequate statistical power to detect potential group differences in behavior. Additionally, the present study focused primarily on individuals with subclinical depression, and the extent to which these findings would generalize to those with more severe symptoms or clinical major depressive disorder is unknown.

CONCLUSIONS

The findings suggest that undergraduates with subclinical depressive symptoms might need to recruit additional compensatory cognitive resources to obtain an equivalent behavioral performance compared with that in undergraduates with none or few depressive symptoms in executive control processing. The current study further provides evidence for the cortical inefficiency theory, which might account for executive control dysfunction in individuals with subclinical depression.

Impaired visual, working, and verbal memory in first-episode, drug-naive patients with major depressive disorder in a Chinese population

Cognitive impairment has been observed in patients with major depressive disorder (MDD). However, it remains unclear whether the deficits in specific cognitive domains are present in first-episode, drug-naïve patients or medicated patients. In the present study, using the CogState battery (CSB) Chinese language version, we evaluated the visual, working, and verbal memory in first-episode drug-naive patients and medicated patients with MDD in a Chinese population. We measured the cognitive function in first-episode drug-naïve patients (n = 36), medicated MDD patients (n = 71), and age- and sex-matched healthy control subjects (n = 59) in a Chinese population. The CSB composite scores in both first-episode drug-naive patients and medicated patients were significantly poorer than those in the healthy control subjects. The CSB sub-scores, including visual, working, and verbal memory were also significantly poorer in both patient groups than those in the healthy control subjects. In contrast, processing speed, attention/vigilance, executive function, spatial working memory, and social cognition were no different from healthy controls, whereas the executive function was significantly better in the medicated patients than in the healthy control subjects and first-episode drug-naïve patients. These findings suggest an impairment in the visual, working, and verbal memory in first-episode, drug-naive MDD patients in a Chinese population.

EEG beta and low gamma power correlates with inattention in patients with major depressive disorder

BACKGROUND

Inattention is a common feature of major depressive disorder (MDD). The aim of this study was to explore the relationship between quantitative electroencephalography (qEEG) power of a specific band and inattention severity in patients with MDD.

METHODS

EEG recordings of 73 patients with MDD were collected in during both eyes closed and eyes open conditions. Inattention was assessed by the inattention sub-scale of the Korean version of the Adult ADHD scale (K-AADHD). The severity of symptoms associated with depression and anxiety was assessed with the Hamilton Rating Scale for Anxiety (HAM-A), the Hamilton Rating Scale for Depression (HAM-D), and the Beck Depression Inventory (BDI). Multiple regression and Hayes mediation model were applied for the statistical analysis to verify the effects of clinical variables on inattention score.

RESULTS

The beta (12-30Hz) and low gamma (30-50Hz) powers in fronto-central regions were negatively correlated with inattention scores. Symptom severity scores strongly predicted inattention scores; in particular, the BDI accounted for 23.9% of the variance. In mediation analysis, BDI fully mediated the path of anxiety to inattention.

LIMITATIONS

The medication effect and comorbidity in our participants were not fully controlled. A subjective assessment tool was hired to measure inattention.

CONCLUSIONS

Beta and low gamma power of the fronto-central regions might be a reliable measure of attention deficits in patients with MDD, which in turn, seems to be related to the severity of subjective depressive symptoms. Further work is needed to confirm this finding on larger, drug and comorbidity-free samples, and to test the clinical utility.

A systematic review of the relationship between psychological disorders or substance use and self-reported cognitive failures

INTRODUCTION

Cognitive failures are errors in normal everyday functioning. Individuals with psychological disorders may possess heightened vulnerability. We sought to review the literature on cognitive failures in psychological disorders to determine the nature of this association, and whether failures relate to neuropsychological performance. We also examine the relationship between cognitive failures and substance use since it is relevant to everyday cognition and co-occurs in many psychological disorders.

METHODS

We conducted a systematic review of self-reported cognitive failures in psychological disorders and substance use, identifying 21 papers in total.

RESULTS

Papers identified studied trauma, mood, and anxiety disorders, and schizophrenia. Substance use papers included nicotine, alcohol, cannabis, and ecstasy use. Cognitive failures were increased in some but not all papers; the most consistent findings were for depression, PTSD, and daily smokers of nicotine. Subjective failures did not correlate closely with neuropsychological outcomes in any disorders. We were unable to discern distinct profiles of failures for each disorder; rather they may reflect emotional dysregulation more broadly.

CONCLUSIONS

The real world cognitive experiences of people with psychological disorders may differ to their performance in the clinic or lab. It is important that self-reports of minor cognitive issues are considered as both a potential risk and a maintaining factor of illness. Substance use also needs to be considered in assessing cognitive failures.

Modulation of executive attention by threat stimulus in test-anxious students

The study examined whether test anxiety (TA) is related to impaired attentional networks under emotional distraction. High and low test-anxious students completed a modified version of the attention network test (ANT) in which emotional distracters, specifically threat-related or neutral words, were embedded in centrally presented hollow arrows in Experiment 1. Results showed a significant reduction in efficiency of the executive attention in test-anxious students compared to controls when the fillers were threat/test-related words. To evaluate the effect of the test adaptation, the original ANT, which utilized no emotional distracter, was employed as a control task in Experiment 2. We then consolidated the data on efficiency of attentional networks, which were derived from both tasks. Contrasting the two tasks showed that TA reduced executive attention in the revised task only, suggesting an enhanced sensitivity provided by the adaptation from the original task. Taken together, these findings indicate that the attentional deficit in test-anxious individuals represents a situation-related defect of a single component of attention rather than an underlying structural and universal attentional deficit. The results support the hypothesis of attentional control theory and contribute to the understanding of attentional mechanisms in individuals with TA.

Impaired conflict resolution and vigilance in euthymic bipolar disorder

Difficulty attending is a common deficit of euthymic bipolar patients. However, it is not known whether this is a global attentional deficit or relates to a specific attentional network. According to the attention network approach, attention is best understood in terms of three functionally and neuroanatomically distinct networks-alerting, orienting, and executive control. In this study, we explored whether and which of the three attentional networks are altered in euthymic Bipolar Disorder (BD). A sample of euthymic BD patients and age-matched healthy controls completed the Attention Network Test for Interactions and Vigilance (ANTI-V) that provided not only a measure of orienting, executive, and alerting networks, but also an independent measure of vigilance (tonic alerting). Compared to healthy controls, BD patients have impaired executive control (greater interference), reduced vigilance (as indexed by a decrease in the d' sensitivity) as well as slower overall reaction times and poorer accuracy. Our results show that deficits in executive attention and sustained attention often persist in BD patients even after complete remission of affective symptoms, thus suggesting that cognitive enhancing treatments programmed to improve these deficits could contribute to improve their functional recovery.

Major depressive disorder is associated with broad impairments on neuropsychological measures of executive function: a meta-analysis and review

Cognitive impairments are now widely acknowledged as an important aspect of major depressive disorder (MDD), and it has been proposed that executive function (EF) may be particularly impaired in patients with MDD. However, the existence and nature of EF impairments associated with depression remain strongly debated. Although many studies have found significant deficits associated with MDD on neuropsychological measures of EF, others have not, potentially due to low statistical power, task impurity, and diverse patient samples, and there have been no recent, comprehensive, meta-analyses investigating EF in patients with MDD. The current meta-analysis uses random-effects models to synthesize 113 previous research studies that compared participants with MDD to healthy control participants on at least one neuropsychological measure of EF. Results of the meta-analysis demonstrate that MDD is reliably associated with impaired performance on neuropsychological measures of EF, with effect sizes ranging from 0.32 to 0.97. Although patients with MDD also have slower processing speed, motor slowing alone cannot account for these results. In addition, some evidence suggests that deficits on neuropsychological measures of EF are greater in patients with more severe current depression symptoms, and those taking psychotropic medications, whereas evidence for effects of age was weaker. The results are consistent with the theory that MDD is associated with broad impairment in multiple aspects of EF. Implications for treatment of MDD and theories of EF are discussed. Future research is needed to establish the specificity and causal link between MDD and EF impairments.

Neurocognitive impairment across the bipolar spectrum

Bipolar disorder is a severe mental illness that affects nearly 4.4% of the general population when bipolar spectrum disorders are taken into account. Neurocognitive impairment is thought to be a core deficit of this illness since it is present during euthymia. In fact, 40-60% of euthymic patients present with neurocognitive disturbances. Not only the clinical factors but also disturbances in neurocognition can influence the functional outcome of BD patients. Hence, further research is needed in order to clarify the relationship between these variables. Despite the growing body of evidence that has emerged during the last decade, no unique neurocognitive profile has been proposed yet for either BD subtype. The majority of the studies recluted heterogeneous samples (including both bipolar I and II) or focused on BD-I patients only. The aim of this review is to give an overall picture of the main neurocognitive disturbances found in the bipolar spectrum and particularly in BD-II, where the findings are more ambiguous. An extensive review of all the literature has been done regarding this subtype (from 1980 until July 2009). Data available until now suggest that deficits are present across the bipolar spectrum (BD-I and BD-II), but they seem slightly more severe in BD-I. The extent to which either subtype share-or not-some similarities is still unknown. More studies are required but it would also be interesting to reach a consensus in the neuropsychological assessment of BD to facilitate comparisons between the different studies.

Alterations of the attentional networks in patients with anxiety disorders

Cognitive theories of emotion try to explain how anxious people attend to the world. Despite the increase in empirical research in this field, the specific or general attentional impairments of patients with anxiety disorder is not well defined. We decided to investigate the relationship between pathological anxiety and attentional mechanisms from the broader perspective of the attentional networks. In our study, patients with anxiety disorders and control participants carried out a task to assess efficiency of three attentional networks: orienting, alerting, and executive control. The main result was that anxiety disorders are related to both reduced effectiveness of the executive control network and difficulties in disengaging attention from invalid cues, even when using emotionally neutral information. This relationship between these attentional networks and anxiety may in part explain the problems in the day-to-day functioning of these patients.

Neurocognitive impairment in adolescent major depressive disorder: state vs. trait illness markers

BACKGROUND

Current treatment outcomes of Major Depressive Disorder (MDD) in adolescents remain suboptimal. Discriminating between state and trait markers of MDD in adolescents would help identify markers that may guide choice of appropriate interventions and help improve longer-term outcome for individuals with the illness.

METHODS

We compared neurocognitive performance in executive function, sustained attention and short-term memory in 20 adolescents with MDD in acute episode (MDDa), 20 previously depressed adolescents in remission (MDDr) and 17 healthy control participants (HC).

RESULTS

There was a group difference that emerged for executive function with increasing task difficulty (p=0.033). MDDa showed impaired executive function, as measured by using more moves to solve 4-move problems on a forward planning task, relative to MDDr and HC (p=0.01, d=0.94 and p=0.015, d=0.77 respectively). MDDa showed more impulsivity as measured by lower response bias (B″) on a sustained attention task than both MDDr and HC (p=0.01, d=0.85 and p=0.008, d=0.49 respectively). Higher impulsivity was associated with more severe depression (r=-0.365, p=0.022) and earlier age of onset of depression (r=0.402, p=0.012) and there was a trend for a correlation between more executive dysfunction and more severe depression (r=0.301 p=0.059) in MDDa and MDDr combined. The three groups did not differ significantly on short-term memory or target detection on the sustained attention task.

LIMITATION

These results need to be replicated in the future with a larger sample size.

CONCLUSION

Executive dysfunction and impulsivity appear to be state-specific markers of MDD in adolescents that are related to depression severity and not present in remission.

Deficits in visual sustained attention differentiate genetic liability and disease expression for schizophrenia from Bipolar Disorder

BACKGROUND

There is mounting evidence for shared genetic liability to psychoses, particularly with respect to Schizophrenia (SZ) and Bipolar Disorder (BD), which may also involve aspects of cognitive dysfunction. Impaired sustained attention is considered a cardinal feature of psychoses but its association with genetic liability and disease expression in BD remains to be clarified.

METHODS

Visual sustained attention was assessed using the Degraded Symbol Continuous Performance Test (DS-CPT) in a sample of 397 individuals consisting of 50 remitted SZ patients, 119 of their first degree relatives, 47 euthymic BD patients, 88 of their first degree relatives and 93 healthy controls. Relatives with a personal history of schizophrenia or bipolar spectrum disorders were excluded. Performance on the DS-CPT was evaluated based on the response criterion (the amount of perceptual evidence required to designate a stimulus as a target) and sensitivity (a signal-detection theory measure of signal/noise discrimination).

RESULTS

We found no effect of genetic risk or diagnosis for either disorder on response criterion. In contrast, impaired sensitivity was seen in SZ patients and to a lesser degree in their relatives but not in BD patients and their relatives. These findings were not attributable to IQ, medication, age of onset or duration of illness.

CONCLUSIONS

Our results argue for the specificity of visual sustained attention impairment in differentiating SZ from BD. They also suggest that compromised visual information processing is a significant contributor to these deficits in SZ.