Cortical abnormalities in adults and adolescents with major depression based on brain scans from 20 cohorts worldwide in the ENIGMA Major Depressive Disorder Working Group

The neuro-anatomical substrates of major depressive disorder (MDD) are still not well understood, despite many neuroimaging studies over the past few decades. Here we present the largest ever worldwide study by the ENIGMA (Enhancing Neuro Imaging Genetics through Meta-Analysis) Major Depressive Disorder Working Group on cortical structural alterations in MDD. Structural T1-weighted brain magnetic resonance imaging (MRI) scans from 2148 MDD patients and 7957 healthy controls were analysed with harmonized protocols at 20 sites around the world. To detect consistent effects of MDD and its modulators on cortical thickness and surface area estimates derived from MRI, statistical effects from sites were meta-analysed separately for adults and adolescents. Adults with MDD had thinner cortical gray matter than controls in the orbitofrontal cortex (OFC), anterior and posterior cingulate, insula and temporal lobes (Cohen's d effect sizes: -0.10 to -0.14). These effects were most pronounced in first episode and adult-onset patients (>21 years). Compared to matched controls, adolescents with MDD had lower total surface area (but no differences in cortical thickness) and regional reductions in frontal regions (medial OFC and superior frontal gyrus) and primary and higher-order visual, somatosensory and motor areas (d: -0.26 to -0.57). The strongest effects were found in recurrent adolescent patients. This highly powered global effort to identify consistent brain abnormalities showed widespread cortical alterations in MDD patients as compared to controls and suggests that MDD may impact brain structure in a highly dynamic way, with different patterns of alterations at different stages of life.

Subcortical brain alterations in major depressive disorder: findings from the ENIGMA Major Depressive Disorder working group

The pattern of structural brain alterations associated with major depressive disorder (MDD) remains unresolved. This is in part due to small sample sizes of neuroimaging studies resulting in limited statistical power, disease heterogeneity and the complex interactions between clinical characteristics and brain morphology. To address this, we meta-analyzed three-dimensional brain magnetic resonance imaging data from 1728 MDD patients and 7199 controls from 15 research samples worldwide, to identify subcortical brain volumes that robustly discriminate MDD patients from healthy controls. Relative to controls, patients had significantly lower hippocampal volumes (Cohen's d=-0.14, % difference=-1.24). This effect was driven by patients with recurrent MDD (Cohen's d=-0.17, % difference=-1.44), and we detected no differences between first episode patients and controls. Age of onset ⩽21 was associated with a smaller hippocampus (Cohen's d=-0.20, % difference=-1.85) and a trend toward smaller amygdala (Cohen's d=-0.11, % difference=-1.23) and larger lateral ventricles (Cohen's d=0.12, % difference=5.11). Symptom severity at study inclusion was not associated with any regional brain volumes. Sample characteristics such as mean age, proportion of antidepressant users and proportion of remitted patients, and methodological characteristics did not significantly moderate alterations in brain volumes in MDD. Samples with a higher proportion of antipsychotic medication users showed larger caudate volumes in MDD patients compared with controls. This currently largest worldwide effort to identify subcortical brain alterations showed robust smaller hippocampal volumes in MDD patients, moderated by age of onset and first episode versus recurrent episode status.

Subcortical brain volume abnormalities in 2028 individuals with schizophrenia and 2540 healthy controls via the ENIGMA consortium

The profile of brain structural abnormalities in schizophrenia is still not fully understood, despite decades of research using brain scans. To validate a prospective meta-analysis approach to analyzing multicenter neuroimaging data, we analyzed brain MRI scans from 2028 schizophrenia patients and 2540 healthy controls, assessed with standardized methods at 15 centers worldwide. We identified subcortical brain volumes that differentiated patients from controls, and ranked them according to their effect sizes. Compared with healthy controls, patients with schizophrenia had smaller hippocampus (Cohen's d=-0.46), amygdala (d=-0.31), thalamus (d=-0.31), accumbens (d=-0.25) and intracranial volumes (d=-0.12), as well as larger pallidum (d=0.21) and lateral ventricle volumes (d=0.37). Putamen and pallidum volume augmentations were positively associated with duration of illness and hippocampal deficits scaled with the proportion of unmedicated patients. Worldwide cooperative analyses of brain imaging data support a profile of subcortical abnormalities in schizophrenia, which is consistent with that based on traditional meta-analytic approaches. This first ENIGMA Schizophrenia Working Group study validates that collaborative data analyses can readily be used across brain phenotypes and disorders and encourages analysis and data sharing efforts to further our understanding of severe mental illness.

Cortical abnormalities in bipolar disorder: an MRI analysis of 6503 individuals from the ENIGMA Bipolar Disorder Working Group

Despite decades of research, the pathophysiology of bipolar disorder (BD) is still not well understood. Structural brain differences have been associated with BD, but results from neuroimaging studies have been inconsistent. To address this, we performed the largest study to date of cortical gray matter thickness and surface area measures from brain magnetic resonance imaging scans of 6503 individuals including 1837 unrelated adults with BD and 2582 unrelated healthy controls for group differences while also examining the effects of commonly prescribed medications, age of illness onset, history of psychosis, mood state, age and sex differences on cortical regions. In BD, cortical gray matter was thinner in frontal, temporal and parietal regions of both brain hemispheres. BD had the strongest effects on left pars opercularis (Cohen's d=-0.293; P=1.71 × 10^-21), left fusiform gyrus (d=-0.288; P=8.25 × 10^-21) and left rostral middle frontal cortex (d=-0.276; P=2.99 × 10^-19). Longer duration of illness (after accounting for age at the time of scanning) was associated with reduced cortical thickness in frontal, medial parietal and occipital regions. We found that several commonly prescribed medications, including lithium, antiepileptic and antipsychotic treatment showed significant associations with cortical thickness and surface area, even after accounting for patients who received multiple medications. We found evidence of reduced cortical surface area associated with a history of psychosis but no associations with mood state at the time of scanning. Our analysis revealed previously undetected associations and provides an extensive analysis of potential confounding variables in neuroimaging studies of BD.

Common and distinct patterns of grey-matter volume alteration in major depression and bipolar disorder: evidence from voxel-based meta-analysis

Finding robust brain substrates of mood disorders is an important target for research. The degree to which major depression (MDD) and bipolar disorder (BD) are associated with common and/or distinct patterns of volumetric changes is nevertheless unclear. Furthermore, the extant literature is heterogeneous with respect to the nature of these changes. We report a meta-analysis of voxel-based morphometry (VBM) studies in MDD and BD. We identified studies published up to January 2015 that compared grey matter in MDD (50 data sets including 4101 individuals) and BD (36 data sets including 2407 individuals) using whole-brain VBM. We used statistical maps from the studies included where available and reported peak coordinates otherwise. Group comparisons and conjunction analyses identified regions in which the disorders showed common and distinct patterns of volumetric alteration. Both disorders were associated with lower grey-matter volume relative to healthy individuals in a number of areas. Conjunction analysis showed smaller volumes in both disorders in clusters in the dorsomedial and ventromedial prefrontal cortex, including the anterior cingulate cortex and bilateral insula. Group comparisons indicated that findings of smaller grey-matter volumes relative to controls in the right dorsolateral prefrontal cortex and left hippocampus, along with cerebellar, temporal and parietal regions were more substantial in major depression. These results suggest that MDD and BD are characterised by both common and distinct patterns of grey-matter volume changes. This combination of differences and similarities has the potential to inform the development of diagnostic biomarkers for these conditions.

Subcortical volumetric abnormalities in bipolar disorder

Considerable uncertainty exists about the defining brain changes associated with bipolar disorder (BD). Understanding and quantifying the sources of uncertainty can help generate novel clinical hypotheses about etiology and assist in the development of biomarkers for indexing disease progression and prognosis. Here we were interested in quantifying case-control differences in intracranial volume (ICV) and each of eight subcortical brain measures: nucleus accumbens, amygdala, caudate, hippocampus, globus pallidus, putamen, thalamus, lateral ventricles. In a large study of 1710 BD patients and 2594 healthy controls, we found consistent volumetric reductions in BD patients for mean hippocampus (Cohen's d=-0.232; P=3.50 × 10-7) and thalamus (d=-0.148; P=4.27 × 10-3) and enlarged lateral ventricles (d=-0.260; P=3.93 × 10-5) in patients. No significant effect of age at illness onset was detected. Stratifying patients based on clinical subtype (BD type I or type II) revealed that BDI patients had significantly larger lateral ventricles and smaller hippocampus and amygdala than controls. However, when comparing BDI and BDII patients directly, we did not detect any significant differences in brain volume. This likely represents similar etiology between BD subtype classifications. Exploratory analyses revealed significantly larger thalamic volumes in patients taking lithium compared with patients not taking lithium. We detected no significant differences between BDII patients and controls in the largest such comparison to date. Findings in this study should be interpreted with caution and with careful consideration of the limitations inherent to meta-analyzed neuroimaging comparisons.

Dissociating neural correlates of cognitive components in mental calculation

Mental calculation is a complex cognitive operation that is composed of a set of distinct functional processes. Using functional magnetic resonance imaging (fMRI), we mapped brain activity in healthy subjects performing arithmetical tasks and control tasks evoking a comparable load on visuo-constructive, linguistic, attentional and mnemonic functions. During calculation, as well as non-mathematical tasks, similar cortical networks consisting of bilateral prefrontal, premotor and parietal regions were activated, suggesting that most of these cortical areas do not exclusively represent modules for calculation but support more general cognitive operations that are instrumental but not specific to mental arithmetic. Significant differences between calculation and the non-mathematical tasks were found in parietal sub-regions, where non-arithmetic number or letter substitution tasks preferentially activated the superior parietal lobules whereas calculation predominantly elicited activation of the left dorsal angular gyrus and the medial parietal cortices. We interpret the latter activations to reflect sub-processes of mental calculation that are related to the processing of numerical representations during exact calculation and to arithmetical fact retrieval. Finally, we found that more complex calculation tasks involving the application of calculation rules increased activity in left inferior frontal areas that are known to subserve linguistic and working memory functions. Taken together, these findings help to embed the specific cognitive operation of calculation into a neural framework that provides the required set of instrumental components. This result may further inform the cognitive modeling of calculation and adds to the understanding of neuropsychological deficit patterns in patients.

Neural activity in human primary motor cortex areas 4a and 4p is modulated differentially by attention to action

The mechanisms underlying attention to action are poorly understood. Although distracted by something else, we often maintain the accuracy of a movement, which suggests that differential neural mechanisms for the control of attended and nonattended action exist. Using functional magnetic resonance imaging (fMRI) in normal volunteers and probabilistic cytoarchitectonic maps, we observed that neural activity in subarea 4p (posterior) within the primary motor cortex was modulated by attention to action, while neural activity in subarea 4a (anterior) was not. The data provide the direct evidence for differential neural mechanisms during attended and unattended action in human primary motor cortex.

Effects of domain-specific interference on brain activation associated with verbal working memory task performance

Previous neuroimaging studies have identified brain regions that underlie verbal working memory in humans. According to these studies a phonological store is located in the left inferior parietal cortex, and a complementary subvocal rehearsal mechanism is implemented by mostly left-hemispheric speech areas. In the present functional magnetic resonance imaging study, classical interfering and non-interfering dual-task situations were used to investigate further the neural correlates of verbal working memory. Verbal working memory performance under non-interfering conditions activated Broca's area, the left premotor cortex, the cortex along the left intraparietal sulcus and the right cerebellum, thus replicating the results from previous studies. By contrast, no significant memory- related activation was found in these areas when silent articulatory suppression prevented the subjects from rehearsal. Instead, this non-articulatory maintenance of phonological information was associated with enhanced activity in several other, particularly anterior prefrontal and inferior parietal, brain areas. These results suggest that phonological storage may be a function of a complex prefronto-parietal network, and not localized in only one, parietal brain region. Further possible implications for the functional organization of human working memory are discussed.

Transdiagnostic commonalities and differences in resting state functional connectivity of the default mode network in schizophrenia and major depression

Schizophrenia and depression are prevalent psychiatric disorders, but their underlying neural bases remains poorly understood. Neuroimaging evidence has pointed towards the relevance of functional connectivity aberrations in default mode network (DMN) hubs, dorso-medial prefrontal cortex and precuneus, in both disorders, but commonalities and differences in resting state functional connectivity of those two regions across disorders has not been formally assessed. Here, we took a transdiagnostic approach to investigate resting state functional connectivity of those two regions in 75 patients with schizophrenia and 82 controls from 4 scanning sites and 102 patients with depression and 106 controls from 3 sites. Our results demonstrate common dysconnectivity patterns as indexed by a significant reduction of functional connectivity between precuneus and bilateral superior parietal lobe in schizophrenia and depression. Furthermore, our findings highlight diagnosis-specific connectivity reductions of the parietal operculum in schizophrenia relative to depression. In light of evidence that points towards the importance of the DMN for social cognitive abilities and well documented impairments of social interaction in both patient groups, it is conceivable that the observed transdiagnostic connectivity alterations may contribute to interpersonal difficulties, but this could not be assessed directly in our study as measures of social behavior were not available. Given the operculum's role in somatosensory integration, diagnosis-specific connectivity reductions may indicate a pathophysiological mechanism for basic self-disturbances that is characteristic of schizophrenia, but not depression.

Domain-specific distribution of working memory processes along human prefrontal and parietal cortices: a functional magnetic resonance imaging study

This study reinvestigated the functional neuroanatomy of phonological and visual working memory in humans. Articulatory suppression was used to deprive the human subjects of species-specific verbal strategies in order to make the functional magnetic resonance imaging results more comparable to findings in non-human primates. Both phonological and visual working memory processes activated similar prefronto-parietal networks but were found to be differentially distributed along several cortical structures, in particular along the anterior and posterior parts of the intermediate frontal sulcus. These results suggest that a domain-specific topographical organization of neural working memory mechanisms in the primate brain is conserved in evolution. However, the findings also underline the critical dynamic influence that the additional availability of language may have on working memory processes and their functional implementation in the human brain.

Neurocognitive functions in euthymic bipolar patients

OBJECTIVE

Meta-analytic findings support the hypothesis of specific neurocognitive deficits for bipolar patients in the domains of attention, processing speed, memory and executive functions. This study aims to show neurocognitive impairment in euthymic patients with bipolar I disorder compared with healthy controls while detailing the impact of medication side-effects or illness characteristics on neuropsychological test performance.

METHOD

Forty euthymic patients with bipolar I disorder were compared with 40 healthy controls in a cross-sectional design. Clinical features and neuropsychological measures of IQ, psychomotor speed, verbal fluency, learning and memory, executive functions and attention were assessed.

RESULTS

Patients without antipsychotic drug use did not differ significantly from healthy controls in any neuropsychological measure. Yet patients treated with antipsychotics showed significant underperformance in the domains of semantic fluency, verbal learning and recognition memory as well as executive functions related to planning abilities, even when clinical features were controlled for.

CONCLUSION

The impact of antipsychotic medication needs to be further clarified for euthymic bipolar patients and should be considered when neuropsychological test performance is interpreted.

A systematic fMRI investigation of the brain systems subserving different working memory components in schizophrenia

Working memory impairment is one of the cardinal cognitive disturbances in schizophrenia and considerable evidence suggests that it can be traced to functional alterations in the brain. The exact allocation of specific deficits to regional specific dysfunctions, however, remains elusive. The aim of this study was to examine the functional integrity of three distinguishable brain systems underlying maintenance-related subprocesses of working memory (articulatory rehearsal, non-articulatory maintenance of phonological information, maintenance of visuospatial information) in patients with schizophrenia. Using an experimental paradigm, which had been designed to selectively activate these different brain systems, we assessed the brain activation of patients and controls with functional magnetic resonance imaging. Compared with controls, patients showed reduced activation of the fronto-opercular, intraparietal and anterior cingulate cortex during the non-articulatory maintenance of phonological information, as well as attenuated deactivation of the hippocampus. Additionally, we found prefrontal activation to depend critically on the patients' current symptom status. During visuospatial maintenance, patients showed impaired activation of the superior parietal, temporal and occipital cortex, combined with enhanced activation of the frontal eye field and the inferior parietal cortex. No abnormal activations were observed during the articulatory rehearsal task. All activation differences were independent of group differences in task performance. Our fine-grained analysis of dysfunctions in particular aspects of working memory circuitry provides evidence for a differential impairment of the brain systems supporting working memory subcomponents in schizophrenia and extends knowledge of the relationship between cognitive deficits, brain activation abnormalities and symptoms in schizophrenia.

The network of brain areas involved in the motion aftereffect

A network of brain areas is expected to be involved in supporting the motion aftereffect. The most active components of this network were determined by means of an fMRI study of nine subjects exposed to a visual stimulus of moving bars producing the effect. Across the subjects, common areas were identified during various stages of the effect, as well as networks of areas specific to a single stage. In addition to the well-known motion-sensitive area MT the prefrontal brain areas BA44 and 47 and the cingulate gyrus, as well as posterior sites such as BA37 and BA40, were important components during the period of the motion aftereffect experience. They appear to be involved in control circuitry for selecting which of a number of processing styles is appropriate. The experimental fMRI results of the activation levels and their time courses for the various areas are explored. Correlation analysis shows that there are effectively two separate and weakly coupled networks involved in the total process. Implications of the results for awareness of the effect itself are briefly considered in the final discussion.

Neural mechanisms of advance preparation in task switching

The preparation effect in task switching can be interpreted to reflect cognitive control processes during the interval between task-cue onset and the trial-stimulus onset which support the flexible and rapid configuration of response dispositions. However, it is an open issue what neural processes underlie this effect. In the present study, healthy volunteers underwent functional magnetic resonance imaging (fMRI) while performing a cued task switching paradigm, in which geometric objects had to be classified according to either color or shape. By manipulating the duration of the cue-target-interval (CTI) in the range between 0 and 1500 ms, we were able to dissociate brain activity changes related to the processing of either the cue or the target. A network of frontal and parietal brain areas was activated during advance preparation for the upcoming task independent of whether the task was switched or repeated. The same brain regions also showed increased neural activity in response to targets without advance preparation in contrast to targets with advance preparation which only elicited activations in areas involved in visual processing and motor execution. These findings strongly argue for a 'task-set activation perspective' on advance preparation in task switching [Altmann, E.M., 2004. Advance preparation in task switching: what work is being done? Psychol. Sci. 15, 616-622.], whereas no empirical support could be found for the 'mental gear changing model' of task switching as no significant brain activity changes were observable in association with task switches, switch costs, or the interaction effect of advance preparation on switch costs. Finally, in the light of previous behavioral studies on interference effects of articulatory suppression on task preparation in humans, the present findings are compatible with the assumption that verbalization mechanisms, e.g., the retrieval of a verbal task or goal representation into working memory may be a functional component of advance configuration of task-sets.

Thalamic volumes in patients with bipolar disorder

There are several hypotheses on functional neuronal networks that modulate mood states and which might form the neuroanatomical basis of bipolar disorder. The thalamus has been reported to be a key structure within the circuits that modulate mood states and might thus play an important role within the aetiology of the bipolar affective disorder. Nevertheless, structural brain imaging studies on the thalamus volume of bipolar patients have shown heterogeneous results. Using structural MRI scanning, we compared the thalamus volume of 41 euthymic bipolar patients to the thalamus volume of 41 well-matched healthy controls. Taking the concomitant medication as a co-variable within the patient group, the analysis of variance revealed a significantly smaller relative volume of the right thalamus in patients not treated with lithium when compared with healthy controls. In contrast, there are no significant differences concerning the thalamus volume between all euthymic bipolar patients and healthy controls. The study only shows findings of a transverse section. No longitudinal analysis was performed. More detailed information on patients' pharmacological histories could not be obtained. In conclusion, this result may be interpreted as an indication of the impact of the thalamus in the pathogenesis of the bipolar I disorder and emphasises the need for further longitudinal studies in bipolar patients with special attention paid to the concomitant medication, in particular to the role of lithium.

The neural substrate of the ideomotor principle revisited: evidence for asymmetries in action-effect learning

Ideomotor theory holds that the perception or anticipatory imagination of action effects activates motor tendencies toward the action that is known to produce these effects, herein referred to as ideomotor response activation (IRA). IRA presupposes that the agent has previously learned which action produces which effects, and that this learning process has created bidirectional associations between the sensory effect codes and the motor codes producing the sensory effects. Here, we refer to this process as ideomotor learning. In the presented fMRI study, we adopted a standard two-phase ideomotor learning paradigm; a mixed between/within-subjects design allowed us to assess the neural substrate of both, IRA and ideomotor learning. We replicated earlier findings of a hand asymmetry in ideomotor processing with significantly stronger IRA by left-hand than right-hand action effects. Crucially, we traced this effect back to more pronounced associative learning for action-contingent effects of the left hand compared with effects of the right hand. In this context, our findings point to the caudate nucleus and the angular gyrus as central structures of the neural network underlying ideomotor learning.

Cerebral correlates of working memory for temporal information

Studies of neural correlates of working memory functions in the auditory-verbal, visuo-spatial and visuo-object domain suggest a category-specific organization of working memory processes in prefrontal cortex. Here, we used fMRI to explore brain areas that underlie different working memory operations directed to the temporal domain, which so far has been widely neglected. Significant activations related to memory updating and comparison processes were found right-accentuated in prefrontal and lateral premotor cortices. Furthermore, both subvocal rhythm encoding and maintenance enhanced left-lateralized activity in Broca's and supplementary motor area as well as in the sensorimotor cortex. Hemispheric lateralization effects of brain activity during temporal processing tasks may depend on the presence or absence of subvocal rehearsal strategies.

Increased right amygdala volume in lithium-treated patients with bipolar I disorder

OBJECTIVE

The amygdala plays a major role in processing emotional stimuli. Fourteen studies using structural magnetic resonance imaging (MRI) have examined the amygdala volume in paediatric and adult patients with bipolar disorder (BD) compared with healthy controls (HC) and reported inconsistent findings. Lithium has been found to increase grey matter volume, and first evidence points towards an effect on regional brain volume such as the amygdala.

METHOD

We examined the amygdala volume of euthymic patients with BD treated with lithium (n = 15), without lithium (n = 24) and HC (n = 41) using structural MRI.

RESULTS

Patients treated with lithium exhibited in comparison to HC a larger right absolute (+17.9%, P = 0.015) and relative (+18%, P = 0.017) amygdala volume. There was no significant difference in amygdala volume between patients without lithium treatment and HC.

CONCLUSION

Lithium appears to have a sustained effect on a central core region of emotional processing and should therefore be considered in studies examining BD.

[S3 guidelines on diagnostics and therapy of bipolar disorders: development process and essential recommendations]

Bipolar disorders are severe psychiatric disorders with extensive individual and health economic consequences. Starting in 2007 the first German evidence and consensus based guideline for diagnostics and treatment of bipolar disorders was developed which holds the potential of increasing confidence of therapists, patients and relatives in the decision-making process and improving healthcare service experiences of patients and relatives. Apart from recommendations for diagnostics and treatment the guidelines provide those for trialogue action, knowledge transfer and self-help and for strategies for healthcare provision of this complex disorder. In the present article the methodology and essential recommendations are outlined and complemented in specific topics by corresponding articles in this special issue. Due to restrictions of the length of this presentation there is the need to refer to the comprehensive version of the guidelines at several points also regarding a detailed discussion of the limitations.