Meta-analyses are essential to summarize the results of the growing number of neuroimaging studies in psychiatry, neurology and allied disciplines. Image-based meta-analyses use full image information (i.e. the statistical parametric maps) and well-established statistics, but images are rarely available making them highly unfeasible. Peak-probability meta-analyses such as activation likelihood estimation (ALE) or multilevel kernel density analysis (MKDA) are more feasible as they only need reported peak coordinates. Signed-differences methods, such as signed differential mapping (SDM) build upon the positive features of existing peak-probability methods and enable meta-analyses of studies comparing patients with controls. In this paper we present a new version of SDM, named Effect Size SDM (ES-SDM), which enables the combination of statistical parametric maps and peak coordinates and uses well-established statistics. We validated the new method by comparing the results of an ES-SDM meta-analysis of studies on the brain response to fearful faces with the results of a pooled analysis of the original individual data. The results showed that ES-SDM is a valid and reliable coordinate-based method, whose performance might be additionally increased by including statistical parametric maps. We anticipate that ES-SDM will be a helpful tool for researchers in the fields of psychiatry, neurology and allied disciplines.

A B S T R A C TNeuroimaging has evolved into a widely used method to investigate the functional neuroanatomy, brain-behaviour relationships, and pathophysiology of brain disorders, yielding a literature of more than 30,000 papers. With such an explosion of data, it is increasingly difficult to sift through the literature and distinguish spurious from replicable findings. Furthermore, due to the large number of studies, it is challenging to keep track of the wealth of findings. A variety of meta-analytical methods (coordinate-based and image-based) have been developed to help summarise and integrate the vast amount of data arising from neuroimaging studies. However, the field lacks specific guidelines for the conduct of such meta-analyses. Based on our combined experience, we propose best-practice recommendations that researchers from multiple disciplines may find helpful. In addition, we provide specific guidelines and a checklist that will hopefully improve the transparency, traceability, replicability and reporting of meta-analytical results of neuroimaging data.

Twelve data-sets comprising 401 people with OCD and 376 healthy controls met inclusion criteria. A new improved voxel-based meta-analytic method, signed differential mapping (SDM), was developed to examine regions of increased and decreased grey matter volume in the OCD group v. control group. Results No between-group differences were found in global grey matter volumes. People with OCD had increased regional grey matter volumes in bilateral lenticular nuclei, extending to the caudate nuclei, as well as decreased volumes in bilateral dorsal medial frontal/anterior cingulate gyri. A descriptive analysis of quartiles, a sensitivity analysis as well as analyses of subgroups further confirmed these findings. Meta-regression analyses showed that studies that included individuals with more severe OCD were significantly more likely to report increased grey matter volumes in the basal ganglia. No effect of current antidepressant treatment was observed. Conclusions The results support a dorsal prefrontal-striatal model of the disorder and raise the question of whether functional alterations in other brain regions commonly associated with OCD, such as the orbitofrontal cortex, may reflect secondary compensatory strategies. Whether the reported differences between participants with OCD and controls precede the onset of the symptoms and whether they are specific to OCD remains to be established.

The complex clinical presentation of OCD can be summarized with a few consistent, temporally stable symptom dimensions. These can be understood as a spectrum of potentially overlapping syndromes that may 1) coexist in any patient, 2) be continuous with normal obsessive-compulsive phenomena, and 3) extend beyond the traditional nosological boundaries of OCD. Although the dimensional structure of obsessive-compulsive symptoms is imperfect, this quantitative approach to phenotypic traits has the potential to advance our understanding of OCD and may aid in the identification of more robust endophenotypes. The need for a dimensional rating scale and suggestions for future research aimed at reducing the burden of this disorder are discussed.

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Context: Obsessive-compulsive disorder (OCD) is clinically heterogeneous, yet most previous functional neuroimaging studies grouped together patients with mixed symptoms, thus potentially reducing the power and obscuring the findings of such studies.Objective: To investigate the neural correlates of washing, checking, and hoarding symptom dimensions in OCD.Design: Symptom provocation paradigm, functional magnetic resonance imaging, block design, and nonparametric brain mapping analyses.Setting: University hospital.Participants: Sixteen patients with OCD (11 inpatients, 5 outpatients) with mixed symptoms and 17 healthy volunteers of both sexes.Intervention: All subjects participated in 4 functional magnetic resonance imaging experiments. They were scanned while viewing alternating blocks of emotional (washing-related, checking-related, hoarding-related, or aversive, symptom-unrelated) and neutral pictures, and imagining scenarios related to the content of each picture type.Main Outcome Measure: Blood oxygenation leveldependent response.Results: Both patients and control subjects experienced increased subjective anxiety during symptom provocation (patients significantly more so) and activated neural regions previously linked to OCD. Analyses of covariance, controlling for depression, showed a distinct pattern of activation associated with each symptom dimension. Patients demonstrated significantly greater activation than controls in bilateral ventromedial prefrontal regions and right caudate nucleus (washing); putamen/globus pallidus, thalamus, and dorsal cortical areas (checking); left precentral gyrus and right orbitofrontal cortex (hoarding); and left occipitotemporal regions (aversive, symptom-unrelated). These results were further supported by correlation analyses within patients, which showed highly specific positive associations between subjective anxiety, questionnaire scores, and neural response in each experiment. There were no consistently significant differences between patients with (n =9) and without (n=7) comorbid diagnoses. Conclusions:The findings suggest that different obsessive-compulsive symptom dimensions are mediated by relatively distinct components of frontostriatothalamic circuits implicated in cognitive and emotion processing. Obsessive-compulsive disorder may be best conceptualized as a spectrum of multiple, potentially overlapping syndromes rather than a unitary nosologic entity.

These findings confirm that the most prominent and replicable structural abnormalities in ADHD are in the basal ganglia. They furthermore suggest that ADHD patients may progressively catch up with their developmental delay with advancing age and that use of stimulant medication may be associated with normalization of structural abnormalities in ADHD, although longitudinal studies are needed to confirm both observations.

This article provides a focused review of the literature on compulsive hoarding and presents a number of options and preliminary recommendations to be considered for DSM-V. In DSM-IV-TR, hoarding is listed as one of the diagnostic criteria for obsessive-compulsive personality disorder (OCPD). According to DSM-IV-TR, when hoarding is extreme, clinicians should consider a diagnosis of obsessive-compulsive disorder (OCD) and may diagnose both OCPD and OCD if the criteria for both are met. However, compulsive hoarding seems to frequently be independent from other neurological and psychiatric disorders, including OCD and OCPD. In this review, we first address whether hoarding should be considered a symptom of OCD and/or a criterion of OCPD. Second, we address whether compulsive hoarding should be classified as a separate disorder in DSM-V, weighing the advantages and disadvantages of doing so. Finally, we discuss where compulsive hoarding should be classified in DSM-V if included as a separate disorder. We conclude that there is sufficient evidence to recommend the creation of a new disorder, provisionally called hoarding disorder. Given the historical link between hoarding and OCD/OCPD, and the conservative approach adopted by DSM-V, it may make sense to provisionally list it as an obsessive-compulsive spectrum disorder. An alternative to our recommendation would be to include it in an Appendix of Criteria Sets Provided for Further Study. The creation of a new diagnosis in DSM-V would likely increase public awareness, improve identification of cases, and stimulate both research and the development of specific treatments for hoarding disorder.