Latent variable analysis of neuropsychological performance has shown that intact cognition consists of interrelated executive functions, including updating (i.e., monitoring working memory store), inhibition (resisting prepotent responses), and shifting (switching between mental sets). An underlying, largely heritable, common factor reflecting general cognitive control capacity also emerges (
2,
3). Across various psychiatric disorders, neuropsychological performance is broadly (i.e., domain nonspecifically) perturbed, with some variations in severity (
4,
5). Evidence from large-scale phenotypic studies has also demonstrated a dimension of general psychopathology that cuts across disorder boundaries (
6). This dimension robustly accounts for lifespan functional impairment and prospective psychopathology above and beyond current symptom-based predictions (
7,
8). Higher loadings on the general psychopathology factor predict worse performance on tasks of working memory and planning as well as limited academic achievement and lower IQ (
7). Thus, a general liability for cognitive dyscontrol, which traverses both cognitive domains and diagnostic boundaries, may be a core feature of mental illness.
Evidence for common, largely heritable liabilities to experiencing general psychopathology as well as cognitive dyscontrol prompts the question of whether there are accompanying structural anomalies seated within the neurocircuitry subserving cognitive control. We recently completed a meta-analysis of volumetric differences in axis I patients and matched control groups (
9). Across 193 whole-brain voxel-based morphometry studies of nearly 16,000 individuals representing diverse diagnostic classes (schizophrenia, bipolar and unipolar depression, anxiety disorders, and substance use disorders), we found that gray matter loss converged across diagnoses in three regions: the dorsal anterior cingulate and the left and right anterior insula. In an independent sample of healthy individuals, we found that lower gray matter volume in these regions predicted worse behavioral performance on measures of higher-level cognitive control but was unrelated to more rudimentary processing speed. These findings suggest a coordinated structural perturbation of a closely interconnected anterior-cingulo-insular or “salience network” across disorders, likely associated with transdiagnostic deficits in executive function tasks.
The insula and anterior cingulate, as part of the broader “salience network” (
10), feature prominently in intact (
11) as well as disordered emotional responding (
12). However, the insula and anterior cingulate are deployed beyond emotional processing, more generally coordinating dynamic neural network interactions in response to contextual demands (
13–
15). Critical to cognitive control is their coordination with the fronto-parietal network to function as a superordinate or “multiple-demand” cognitive processing network (
16–
26). That is, in tasks ranging from working memory to inhibiting irrelevant information and selecting competing task-relevant responses (
17), the dorsal anterior cingulate and left and right anterior insula extending to the ventrolateral prefrontal cortex are recruited in conjunction with the midcingulate cortex extending into the presupplementary motor area; the left dorsolateral prefrontal cortex extending from the middle frontal gyrus to the inferior frontal junction/gyrus and premotor cortex; and the inferior parietal cortex extending into the intraparietal sulcus. Findings have been mixed in terms of which multiple-demand network nodes show dissociable sensitivity to phasic (i.e., moment-to-moment) versus sustained (i.e., set maintenance) cognitive demands (e.g.,
20–
22). However, the salience network (often referred to as the cingulo-opercular network in the cognitive task literature) and the fronto-parietal network reliably coordinate as subnetworks of a broader, coherent multiple-demand network. Similar to the latent or common cognitive control factor observed in behavioral measures of cognitive processing, the activity of this network suggests a “common core” recruited across diverse cognitive challenges (
18).
Method
Experiment Inclusion Criteria and Identification
Articles were identified by searching PubMed for functional neuroimaging experiments of cognitive control tasks published through June 2015 that compared patients with axis I disorders to matched control participants (
Figure 1). Experiments were eligible if they 1) examined cognitive control tasks with functional neuroimaging, 2) performed whole-brain analysis, 3) included a comparison between patients with axis I disorders and matched healthy control participants during cognitive challenges, and 4) reported coordinates in a defined stereotaxic space (e.g., Talairach or Montreal Neurological Institute [MNI] space).
Experimental procedures must have included diagnostic interview of axis I patients and control participants, with patient groups exceeding the clinical threshold for diagnosis. A psychotic disorders category comprised schizophrenia and schizoaffective, schizophreniform, and delusional disorders. A nonpsychotic disorders category comprised bipolar and unipolar (major depression, dysthymia) depressive disorders, anxiety disorders (including obsessive-compulsive and posttraumatic stress disorders), and substance use disorders (mixed substance abuse and/or dependence). Experiments with fully remitted patient samples were excluded.
Individuals with a principal diagnosis of a depressive or a bipolar disorder who also presented with psychotic features were excluded by criteria in the original experiments. Across disorders, patient participants included those with first-episode and chronic disorder manifestations, including interepisode states of bipolar and psychotic disorders. The substance use disorders included chronic users of a range of substances, currently active or abstinent, but not in acute withdrawal. Experiments were selected to capture lifespan patterns and thus included participants ranging in age from childhood through older adulthood. Axis I diagnoses presenting predominantly in childhood (e.g., attention deficit hyperactivity disorder) or those associated with altered developmental trajectories of brain structures inherent to expression of disorder phenotypes (e.g., autism spectrum disorders) were excluded.
Articles with experimental tasks probing a wide range of processes related to cognitive control were included, categorized into eight domains: conflict monitoring, performance monitoring, response inhibition, response selection, set shifting, verbal fluency, recognition memory, and working memory. A ninth category, “other,” included 18 disparate experiments that did not cohere with one of these domains (see Table S1 in the data supplement that accompanies the online edition of this article). To target substrates of higher-order cognitive control, experiments that focused on simple processing speed or orienting in the context of passive perception (e.g., oddball discrimination) were excluded. Cognitive processing experiments with embedded affective manipulations (e.g., affective stimuli, mood induction) were also excluded.
Peak coordinates for whole brain between-group comparisons under cognitive challenge were required. Interactions were included if follow-up tests clarified patterns of patient hyper- versus hypoactivation during cognitive challenge. Experiments reporting results only for small-volume correction or within a region of interest were excluded. Articles with reported contrasts that did not reflect cognitive demand were excluded. If multiple contrasts were reported in a single paper, only those pertaining to the most challenging condition were included. All coordinates reported in Talairach space were converted into MNI space (
27).
Activation Likelihood Estimation (ALE) Meta-analysis
The revised ALE algorithm, implemented in MATLAB, was used to identify areas of convergence of reported coordinates for patient/control differences in activation during cognitive control tasks higher than expected under a random spatial association (
28,
29,
30; see also the Supplementary Methods section in the
online data supplement). The resulting nonparametric p values were thresholded at a cluster-level family-wise-error-corrected threshold of p<0.05 (cluster-forming threshold at voxel-level p<0.005) and transformed into z scores for display. To avoid results dominated by one or two individual experiments and to have sufficient power to detect moderately sized effects, ALE analyses were limited to those contrasts with at least 20 experiments (
31).
We conducted the following analyses:
1.
Pooling across coordinates of hypo- and hyperactivation in patients relative to controls to identify transdiagnostic patterns of “aberrant activation.”
2.
A conjunction between these results and the multiple-demand network from three large meta-analyses in healthy participants (
25, retrieved through ANIMA [
32],
http://anima.fz-juelich.de).
3.
A conjunction with the nodes of common gray matter decrease revealed by Goodkind et al. (
9).
4.
Separate ALE analyses on hyper- or hypoactivation coordinates (i.e., patient > control or control > patient).
5.
Guided by our previous work (
9) and phenotypic structural models (
33), we distinguished between psychotic and nonpsychotic disorders. Given sufficient numbers of experiments (
31), we performed ALE by broad diagnostic groupings (i.e., schizophrenia, bipolar and unipolar depression, anxiety disorders, and substance use disorders).
6.
Follow-up analyses on extracted data (probability of voxelwise activation from the modeled activation maps) in significant clusters to examine the contribution of demographic, disorder, medication, and task-related factors.
Nonparametric Wilcoxon signed rank tests, Kruskal-Wallis tests, and Mann-Whitney U tests were utilized as warranted.
Discussion
In a meta-analysis of cognitive control tasks across axis I disorders, we observed a transdiagnostic pattern of aberrant brain activation in regions corresponding to the well-established multiple-demand network (
16–
26), including the left prefrontal cortex (from premotor to middorsolateral prefrontal cortex), the right insula extending to the ventrolateral prefrontal cortex, the right intraparietal sulcus, and the anterior midcingulate/presupplementary motor cortex. Abnormal activation was also observed in a separate, more anterior dorsal anterior cingulate cluster (as well as the insula), suggestive of concurrent disruption in regions we previously observed (
9) as transdiagnostically prone to reduced gray matter.
Unlike patient hypoactivation, patient hyperactivation was isolated to the anterior midcingulate/presupplementary motor cortex. Consistent with a role in the implementation and maintenance of task sets (
34) as well as the translation to overt action (
35), patient hyperactivation in the anterior midcingulate/presupplementary motor cortex was primarily driven by experiments for which predominantly medicated patients performed on par with control participants, as opposed to those for which patients performed worse. Increased anterior midcingulate/presupplementary motor cortex activation in patients relative to control participants may reflect a compensatory process for maintaining intact performance amid deficiencies in other network nodes (i.e., proactive/reactive control [
36]).
Given that the swath of cortex extending from the anterior to the midcingulate/presupplementary motor cortex has been characterized as part of a coherent salience network (
10,
15), the discordant hypo- and hyperactivation observed here between the more anterior and posterior cingulate, respectively, might seem unexpected. However, parcellation of the intrinsic functional connectivity of the anterior insula has revealed subnetworks that differentiate these regions. While both the ventral and dorsal anterior insula support cognitive processing (
36), the dorsal portion is more closely coupled with the anterior midcingulate/presupplementary motor cortex (marked here by patient hyperactivation) and appears to promote cognitive flexibility (
37). The ventral anterior insula (marked here by patient hypoactivation) is more closely coupled with the anterior dorsal cingulate (marked here by corresponding hypoactivation) and relates more to motivational engagement (
36). Whole brain graph theoretical approaches have similarly revealed this distinction, leading to speculation that the more anterior cingulate subnetwork is more characteristic of the salience network, whereas the more posterior cingulate subnetwork is more representative of a cingulo-opercular task control network (
38).
Differences in the extent of disruption also emerged between psychotic and nonpsychotic disorders. Psychotic disorders, particularly schizophrenia, showed pronounced hypoactivation of the left lateral prefrontal cluster, particularly the more posterior portion. Meta-analytic coactivation-based parcellation of this region has suggested that while the left prefrontal cortex is broadly recruited for adaptive cognitive control, the predominant processes are typically more top-down, moving anteriorly from the premotor to the middorsolateral prefrontal cortex (
39,
40). The consistent hypoactivation across this cortical gradient, including the more posterior portion subserving more rudimentary processes, may reflect the broad and more severe cross-domain disruption of neuropsychological performance in schizophrenia relative to other disorders (
4). In contrast, particularly convergent hypoactivation across disorders emerged in the right anterior insula/ventrolateral prefrontal cortex. This network switchboard or hub appears especially vulnerable to both gray matter loss and functional impairment across psychopathology.
Concurrent disruptions in the salience and multiple-demand networks highlight a means by which transdiagnostic gray matter reduction in the dorsal anterior cingulate and insula might influence cognitive control capacity and, furthermore, how affective and neurocognitive deficits in psychopathology may so often be expressed simultaneously. That is, these highly coordinated regions are sensitive to demands on either cognitive control or emotional processing (
17).
Our findings are also consistent with the broader role of the anterior cingulate and insular cortices as coordinating network interactions in the service of goal-directed behavior (
41,
42). For example, recent work on causal interactions among nodes of multiple-demand and salience networks (
43,
44) suggests that the anterior insula amplifies salience detection in the anterior and midcingulate cortices in a manner proportional to both cognitive demand and individual capacity. This in turn prompts activation of the fronto-parietal subnetwork, particularly lateral prefrontal regions and the parietal cortex. Furthermore, a coactivation-based parcellation of the lateral prefrontal cortex across cognitive paradigms (
45) revealed two functional subregions, with the anterior region preferentially connected to the anterior cingulate and the posterior region to the intraparietal sulci. In short, accumulating evidence supports strong functional integration among the salience and multiple-demand networks and subnetworks during intact cognitive processing, and the present findings suggest that their coordination is vulnerable to disruption across disorders.
Our study has several limitations. First, the number of included experiments varied substantially among the cognitive domains, as it did among the disorders. We observed strong evidence of a domain general cognitive control disruption in fronto-parietal-cingular-insular networks, with limited diagnosis-specific effects. The latter may reflect the typically less severe neuropsychological impairments of disorders other than schizophrenia (
4), or simply a lack of power due to the limited corpus of published papers for some disorders, or the fact that ALE probes spatial convergence without accounting for individual effect sizes. Additionally, polythetic diagnostic schemes, comorbidity, and the inherent difficulty of establishing consensus on principal disorder could hamper detection of cognitive control impairment profiles of putatively “pure” disorder manifestations and instead contribute to common patterns. Likely influential factors, such as medication types, illness duration, and comorbidity, could not be comprehensively assessed because of incomplete reporting across studies. Furthermore, given the paucity of published study sets in children and older adults, our findings are most applicable to (younger) adults. Lastly, while this is the most comprehensive meta-analysis of functional neuroimaging of cognitive processing in axis I disorders, the included studies do not represent the whole of the extant literature, including the vast number of studies focused on specific regions of interest.