Local cerebral glucose metabolic rates in obsessive-compulsive disorder. A comparison with rates in unipolar depression and in normal controls

Perseveration on a reversal-learning task correlates with rates of self-directed behavior in nonhuman primates

In humans and several nonhuman animals, repetitive behavior is associated with deficits on executive function tasks involving response inhibition. We tested for this relationship in nonhuman primates by correlating rates of normative behavior to performance on a reversal-learning task in which animals were required to inhibit a previously learned rule. We focused on rates of self-directed behavior (scratch, autogroom, self touch and manipulation) because these responses are known indicators of arousal or anxiety in primates, however, we also examined rates of other categories of behavior (e.g., locomotion). Behavior rates were obtained from 14 animals representing three nonhuman primate species (Macaca silenus, Saimiri sciureus, Cebus apella) living in separate social groups. The same animals were tested on a reversal-learning task in which they were presented with a black and a grey square on a touch screen and were trained to touch the black square. Once animals learned to select the black square, reward contingencies were reversed and animals were rewarded for selecting the grey square. Performance on the reversal-learning task was positively correlated to self-directed behavior in that animals that exhibited higher rates of self-directed behavior required more trials to achieve reversal. Reversal learning was not correlated to rates of any other category of behavior. Results indicate that rates of behavior associated with anxiety and arousal provide an indicator of executive function in nonhuman primates. The relationship suggests continuity between nonhuman primates and humans in the link between executive functioning and repetitive behavior.

The reticular-activating hypofrontality (RAH) model of acute exercise

We present here a comprehensive, neurocognitive model to account for the psychological consequences of acute exercise. There is a substantial amount of disparate research and the proposed mechanistic explanation meaningfully integrates this body of brain and behavioral data into a single, unified model. The model's central feature is a cascading, two-step process. First, exercise engages arousal mechanisms in the reticular-activating system. This activation process, which involves a number of neurotransmitter systems, has several interrelated effects on cognition and emotion but, in general, has evolved to facilitate implicit information processing. Second, exercise disengages the higher-order functions of the prefrontal cortex. This deactivation process, which is caused in part by resource limitations, also has several interrelated effects but, in general, has evolved to keep the inefficient explicit system and unhelpful emotional processes from compromising the implicit system's functioning when optimal motor execution is needed most. In this article, we review evidence in support of this reticular-activating hypofrontality (RAH) model of acute exercise and place it into a larger evolutionary context.

Obsessive-compulsive behavior disappearing after left capsular genu infarction

This case report describes a 74-year-old woman with obsessive-compulsive behaviors that disappeared following a left capsular genu infarction. The patient's capsular genu infarction likely resulted in thalamocortical disconnection in the cortico-basal ganglia-thalamocortical loop, which may have caused the disappearance of her obsessive-compulsive symptoms. The fact that anterior capsulotomy has been demonstrated to be effective for treating refractory obsessive-compulsive disorder further supports this hypothesis.

Frontostriatal activation in patients with obsessive-compulsive disorder before and after cognitive behavioral therapy

BACKGROUND

Cognitive behavioral therapy (CBT) with exposure and response prevention (ERP) is the psychotherapeutic treatment of choice for obsessive-compulsive disorder (OCD). However, little is known about the impact of CBT on frontostriatal dysfunctioning, known to be the neuronal correlate of OCD.

METHOD

A probabilistic reversal learning (RL) task probing adaptive strategy switching capabilities was used in 10 unmedicated patients with OCD and 10 healthy controls during an event-related functional magnetic resonance imaging (fMRI) experiment. Patients were scanned before and after intensive CBT, controls twice at comparable intervals.

RESULTS

Strategy change within the RL task involved activity in a broad frontal network in patients and controls. No significant differences between the groups or in group by time interactions were detected in a whole-brain analysis corrected for multiple comparisons. However, a reanalysis with a more lenient threshold revealed decreased responsiveness of the orbitofrontal cortex and right putamen during strategy change before treatment in patients compared with healthy subjects. A group by time effect was found in the caudate nucleus, demonstrating increased activity for patients over the course of time. Patients with greater clinical improvement, reflected by greater reductions in Yale-Brown Obsessive Compulsive Scale (YBOCS) scores, showed more stable activation in the pallidum.

CONCLUSIONS

Although these findings are preliminary and need to be replicated in larger samples, they indicate a possible influence of psychotherapy on brain activity in core regions that have been shown to be directly involved both in acquisition of behavioral rules and stereotypes and in the pathophysiology of OCD, the caudate nucleus and the pallidum.

Update on repetitive transcranial magnetic stimulation in obsessive-compulsive disorder: different targets

Obsessive-compulsive disorder (OCD) is a chronic, disabling disorder. Ten percent of patients remain treatment refractory despite several treatments. For these severe, treatment-refractory patients, repetitive transcranial magnetic stimulation (rTMS) has been suggested as a treatment option. Since 1997, in published trials, a total of 110 OCD patients have been treated with rTMS. This review aims to provide an update on rTMS treatment in patients with OCD. First, the mechanism of action is discussed, followed by the efficacy and side effects of rTMS at various brain targets, and finally implications for the future. Due to the lack of studies with comparable stimulation or treatment parameters and with reliable designs, it is difficult to draw clear conclusions. In general, rTMS appears to be effective in open-label studies; however, this has not yet been replicated in randomized, sham-controlled trials.

Decrease of prefrontal metabolism after subthalamic stimulation in obsessive-compulsive disorder: a positron emission tomography study

BACKGROUND

High-frequency bilateral subthalamic nucleus (STN) deep brain stimulation (DBS) is a promising treatment in refractory obsessive-compulsive disorder (OCD).

METHOD

Using the crossover, randomized, and double-blind procedure adopted by the STOC study, 10 patients treated with high-frequency bilateral STN DBS underwent am 18-fluorodeoxyglucose positron emission tomography (PET) investigation to highlight the neural substratum of this therapeutic approach.

RESULTS

The median Yale-Brown Obsessive Compulsive Scale (Y-BOCS) scores for all 10 patients were 31 (minimum = 18, maximum = 36) with "Off-Stimulation" status and 19 (minimum = 0, maximum = 30) with "On-Stimulation" status (p = .05). The OCD patients in Off-Stimulation status showed a hypermetabolism in the right frontal middle and superior gyri, right parietal lobe, postcentral gyrus, and bilateral putamen compared with healthy control subjects. A significant decrease in cerebral metabolism was observed in the left cingulate gyrus and the left frontal medial gyrus in On-Stimulation conditions compared with Off-Stimulation conditions. In addition, the improvement assessed by Y-BOCS scores during the On-Stimulation conditions was positively correlated with PET signal changes at the boundary of the orbitofrontal cortex and the medial prefrontal cortex, between PET signal changes and the Y-BOCS scores modifications in On-Stimulation status.

CONCLUSION

This study suggests that the therapeutic effect of STN DBS is related to a decrease in prefrontal cortex metabolism.

Effects of behavioral therapy or pharmacotherapy on brain glucose metabolism in subjects with obsessive-compulsive disorder as assessed by brain FDG PET

This prospective study investigated the effect of pharmacotherapy (PT) and cognitive behavioral therapy (CBT) on cerebral glucose metabolism in adults with obsessive-compulsive disorder (OCD). Dynamic positron emission tomography (PET) of the brain with F-18-fluorodeoxyglucose (FDG) was performed before and after treatment in 16 subjects diagnosed for OCD for at least 2 years (PT: n=7). Pre-to-post-treatment change of scaled local metabolic rate of glucose (SLMRGlc) was assessed separately in therapy responders and non-responders. Correlation was tested between SLMRGlc change and change of OCD, depression, or anxiety symptoms. SLMRGlc increased in the right caudate after successful therapy. The increase tended to correlate with the improvement of OCD symptom severity. The finding of increased local caudate activity after successful therapy is in contrast to most previous studies. Possible explanations include effects of therapy on concomitant depression symptoms and/or the large proportion of early-onset OCD in the present sample.

Corticostriatal functional connectivity in non-medicated patients with obsessive-compulsive disorder

The basal ganglia represents a key component of the pathophysiological model for obsessive-compulsive disorder (OCD). This brain region is part of several neural circuits, including the orbitofronto-striatal circuit and dorsolateral prefronto-striatal circuit. There are, however, no published studies investigating those circuits at a network level in non-medicated patients with OCD. Resting state functional magnetic resonance imaging scans were obtained from 20 non-medicated patients with OCD and 23 matched healthy volunteers. Voxelwise statistical parametric maps testing strength of functional connectivity of three striatal seed regions of interest (ROIs) with remaining brain regions were calculated and compared between groups. We performed additional correlation analyses between strength of connectivity and the severity scores for obsessive-compulsive symptoms, depression, and anxiety in the OCD group. Positive functional connectivity with the ventral striatum was significantly increased (P(corrected) < .05) in the orbitofrontal cortex, ventral medial prefrontal cortex and dorsal lateral prefrontal cortex of subjects with OCD. There was no significant correlation between measures of symptom severity and the strength of connectivity (P(uncorrected) < .001). This is the first study to investigate the corticostriatal connectivity in non-medicated patients with OCD. These findings provide the first direct evidence supporting a pathophysiological model involving basal ganglia circuitry in OCD.

fMRI tracks reductions in repetitive behaviors in autism: two case studies

Autism is characterized by abnormal prefrontal brain activation during cognitive control, a potential biomarker of repetitive behaviors. In this proof-of-principle study, functional magnetic resonance imaging (fMRI) was used to examine brain activity during an oddball task in two high-functioning males with autism before and after 12 weeks of treatment with citalopram, a selective serotonin reuptake inhibitor. One participant showed marked reductions in repetitive behaviors whereas the other showed mild worsening. Brain activation in relevant prefrontal regions increased in only the participant whose repetitive behavior symptoms improved. These findings suggest that fMRI may elucidate potential mechanisms of action of targeted autism interventions.

Amygdala activation in response to facial expressions in pediatric obsessive-compulsive disorder

BACKGROUND

Exaggerated amygdala activation to threatening faces has been detected in adults and children with anxiety disorders, compared to healthy comparison (HC) subjects. However, the profile of amygdala activation in response to facial expressions in obsessive-compulsive disorder (OCD) may be a distinguishing feature; a prior study found that compared with healthy adults, adults with OCD exhibited less amygdala activation to emotional and neutral faces, relative to fixation [Cannistraro et al. (2004). Biological Psychiatry 56:916-920].

METHODS

In the current event-related functional magnetic resonance imaging (fMRI) study, a pediatric OCD sample (N=12) and a HC sample (N=17) performed a gender discrimination task while viewing emotional faces (happy, fearful, disgusted) and neutral faces.

RESULTS

Compared to the HC group, the OCD group showed less amygdala/hippocampus activation in all emotion and neutral conditions relative to fixation.

CONCLUSIONS

Like previous reports in adult OCD, pediatric OCD may have a distinct neural profile from other anxiety disorders, with respect to amygdala activation in response to emotional stimuli that are not disorder specific.

Predictors of treatment response to fluvoxamine in obsessive-compulsive disorder: an fMRI study

Recent neuroimaging studies suggest that the pathophysiology of obsessive-compulsive disorder (OCD) may involve more widely distributed large-scale brain systems, including the parietal, occipital, and cerebellar areas, rather than the conventional orbitofronto-striatal model. We hypothesized that not only orbitofrontal cortex and caudate nucleus activities but also posterior brain regions might be associated with subsequent treatment response to serotonin reuptake inhibitors in OCD. The participants were 17 patients with OCD. Each patient was required to undergo fluvoxamine pharmacotherapy for 12 weeks. Before treatment, fMRI images of the subjects were obtained in the context of a symptom-provocation paradigm. The percentage changes in total Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) scores, from pre- to post-treatment, served as the index of treatment response. Statistical Parametric Mapping was used to identify brain loci where pre-treatment brain activation significantly correlated with the subsequent treatment response. Fifteen of 17 patients completed the 12-week treatment. During the symptom provocation task, patients showed brain activation in the left superior temporal gyrus (STG), left precuneus, left frontal cortices, right cerebellum, and right frontal cortices. We found that pre-treatment activation in the right cerebellum (Z-score=5.10, x,y,z=22,-84,-18) and the left STG (Z-score=4.95, x,y,z=-62,-22,0) was positively correlated with the improvement in the Y-BOCS score. Our results suggest that pre-treatment activation in the right cerebellum and in the left STG predict subsequent reduction in OCD symptom severity. There is every possibility that fMRI can be used as a tool to predict treatment response.

Increased neural response to fear in patients recovered from depression: a 3T functional magnetic resonance imaging study

BACKGROUND

Previous imaging studies have revealed that acute major depression is characterized by altered neural responses to negative emotional stimuli. Typically, responses in limbic regions such as the amygdala are increased while activity in cortical regulatory regions such as the dorsolateral prefrontal cortex (DLPFC) is diminished. Whether these changes persist in unmedicated recovered patients is unclear.

METHOD

We used functional magnetic resonance imaging to examine neural responses to emotional faces in a facial expression-matching task in 16 unmedicated recovered depressed patients and 21 healthy controls.

RESULTS

Compared with controls, recovered depressed patients had increased responses bilaterally to fearful faces in the DLPFC and right caudate. Responses in the amygdala did not distinguish the groups.

CONCLUSIONS

Our findings indicate that clinical recovery from depression is associated with increased activity in the DLPFC to negative emotional stimuli. We suggest that this increase may reflect a compensatory cortical control mechanism with the effect of limiting emotional dysregulation in limbic regions such as the amygdala.

Time course of attentional bias in anxiety: emotion and gender specificity

Anxiety is characterized by cognitive biases, including attentional bias to emotional (especially threatening) stimuli. Accounts differ on the time course of attention to threat, but the literature generally confounds emotional valence and arousal and overlooks gender effects, both addressed in the present study. Nonpatients high in self-reported anxious apprehension, anxious arousal, or neither completed an emotion-word Stroop task during event-related potential (ERP) recording. Hypotheses differentiated time course of preferential attention to emotional stimuli. Individuals high in anxious apprehension and anxious arousal showed distinct early ERP evidence of preferential processing of emotionally arousing stimuli along with some evidence for gender differences in processing. Healthy controls showed gender differences at both early and later processing stages. The conjunction of valence, arousal, and gender is critical in the time course of attentional bias.

The neurobiology of repetitive behavior: …and men

In young, typically developing children, repetitive behavior similar to that in certain neuropsychiatric syndromes is common. Whereas this behavior is adaptive in typical development, in many disorders it forms a core component of symptoms and causes prominent impairment in the daily life of affected individuals. Understanding the neurobiological mechanisms involved repetitive behavior will improve our understanding of the pathogenesis of developmental neuropsychiatric disorders, stimulating novel approaches to these conditions. However, studies on the neurobiology of human repetitive behavior have often been limited to distinct conditions and generalization has been hindered by inconsistent terminology. In this paper, we synthesize the 'disorder-driven' literature, building on findings from fundamental animal research and translational models. These findings suggest a model for classifying repetitive behavior by its neuroanatomical correlates.

Probing compulsive and impulsive behaviors, from animal models to endophenotypes: a narrative review

Failures in cortical control of fronto-striatal neural circuits may underpin impulsive and compulsive acts. In this narrative review, we explore these behaviors from the perspective of neural processes and consider how these behaviors and neural processes contribute to mental disorders such as obsessive-compulsive disorder (OCD), obsessive-compulsive personality disorder, and impulse-control disorders such as trichotillomania and pathological gambling. We present findings from a broad range of data, comprising translational and human endophenotypes research and clinical treatment trials, focussing on the parallel, functionally segregated, cortico-striatal neural projections, from orbitofrontal cortex (OFC) to medial striatum (caudate nucleus), proposed to drive compulsive activity, and from the anterior cingulate/ventromedial prefrontal cortex to the ventral striatum (nucleus accumbens shell), proposed to drive impulsive activity, and the interaction between them. We suggest that impulsivity and compulsivity each seem to be multidimensional. Impulsive or compulsive behaviors are mediated by overlapping as well as distinct neural substrates. Trichotillomania may stand apart as a disorder of motor-impulse control, whereas pathological gambling involves abnormal ventral reward circuitry that identifies it more closely with substance addiction. OCD shows motor impulsivity and compulsivity, probably mediated through disruption of OFC-caudate circuitry, as well as other frontal, cingulate, and parietal connections. Serotonin and dopamine interact across these circuits to modulate aspects of both impulsive and compulsive responding and as yet unidentified brain-based systems may also have important functions. Targeted application of neurocognitive tasks, receptor-specific neurochemical probes, and brain systems neuroimaging techniques have potential for future research in this field.

The neurocircuitry of fear, stress, and anxiety disorders

Anxiety disorders are a significant problem in the community, and recent neuroimaging research has focused on determining the brain circuits that underlie them. Research on the neurocircuitry of anxiety disorders has its roots in the study of fear circuits in animal models and the study of brain responses to emotional stimuli in healthy humans. We review this research, as well as neuroimaging studies of anxiety disorders. In general, these studies have reported relatively heightened amygdala activation in response to disorder-relevant stimuli in post-traumatic stress disorder, social phobia, and specific phobia. Activation in the insular cortex appears to be heightened in many of the anxiety disorders. Unlike other anxiety disorders, post-traumatic stress disorder is associated with diminished responsivity in the rostral anterior cingulate cortex and adjacent ventral medial prefrontal cortex. Additional research will be needed to (1) clarify the exact role of each component of the fear circuitry in the anxiety disorders, (2) determine whether functional abnormalities identified in the anxiety disorders represent acquired signs of the disorders or vulnerability factors that increase the risk of developing them, (3) link the findings of functional neuroimaging studies with those of neurochemistry studies, and (4) use functional neuroimaging to predict treatment response and assess treatment-related changes in brain function.

Duration effect of obsessive-compulsive disorder on cognitive function: a functional MRI study

BACKGROUND

The inconsistency of previous reports examining cognitive function in obsessive-compulsive disorder (OCD) suggests its heterogeneity. In this study, we examined the effect of illness duration on cognitive function in OCD.

METHODS

We examined the cognitive function of 32 OCD patients and 16 healthy volunteers by neuropsychological tests and functional magnetic resonance imaging while they performed the Stroop and N-back tasks to assess attention and nonverbal memory. The patients were divided into two groups by illness duration: a short-term group (n=17, 5.5+/-3.1 years) and a long-term group (n=15, 20.3+/-6.1 years). Statistical analysis was performed to determine the differences between these two groups and the normal control group (n=16).

RESULTS

The long-term group showed attention deficit and nonverbal memory dysfunction on the neuropsychological tests. In contrast, on functional magnetic resonance imaging, the short-term group showed weaker activation of the right caudate during the Stroop task and stronger activation of the right dorso-lateral prefrontal cortex during the N-back task than the long-term and normal control groups.

CONCLUSIONS

The results suggested that abnormal brain activation occurs in the early phase of OCD and that the long-term persistence of OCD might involve a decline in cognitive function.

Endophenotypes of obsessive-compulsive disorder: rationale, evidence and future potential

Obsessive-compulsive disorder (OCD) is a heritable and debilitating neuropsychiatric condition. Attempts to delineate genetic contributions have met with limited success, and there is an ongoing search for intermediate trait or vulnerability markers rooted in the neurosciences. Such markers would be valuable for detecting people at risk of developing the condition, clarifying etiological factors and targeting novel treatments. This review begins with brief coverage of the epidemiology of OCD, and presents a hierarchical model of the condition. The advantages of neuropsychological assessment and neuroimaging as objective measures of brain integrity and function are discussed. We describe the concept of endophenotypes and examples of their successful use in medicine and psychiatry. Key areas of focus in the search for OCD endophenotypes are identified, such as measures of inhibitory control and probes of the integrity of orbitofrontal and posterior parietal cortices. Finally, we discuss exciting findings in unaffected first-degree relatives of patients with OCD that have led to the identification of several candidate endophenotypes of the disorder, with important implications for neurobiological understanding and treatment of this and related conditions.

Bipolar and major depressive disorder: neuroimaging the developmental-degenerative divide

Both major depressive disorder and bipolar disorder are the subject of a voluminous imaging and genetics literature. Here, we attempt a comprehensive review of MRI and metabolic PET studies conducted to date on these two disorders, and interpret our findings from the perspective of developmental and degenerative models of illness. Elevated activity and volume loss of the hippocampus, orbital and ventral prefrontal cortex are recurrent themes in the literature. In contrast, dorsal aspects of the PFC tend to display hypometabolism. Ventriculomegaly and white matter hyperintensities are intimately associated with depression in elderly populations and likely have a vascular origin. Important confounding influences are medication, phenotypic and genetic heterogeneity, and technological limitations. We suggest that environmental stress and genetic risk variants interact with each other in a complex manner to alter neural circuitry and precipitate illness. Imaging genetic approaches hold out promise for advancing our understanding of affective illness.

Working memory dysfunction in obsessive-compulsive disorder: a neuropsychological and functional MRI study

Previous neuropsychological studies indicate that OCD subtypes such as checking rituals might be associated with a working memory deficit. On the other hand, functional neuroimaging studies found functional abnormalities of the frontal cortex and subcortical structures in OCD. Combined with functional imaging method, we applied neuropsychological batteries to demonstrate a working memory deficit in OCD by comparison with normal controls. In addition, working memory and brain activation were further examined with symptom-based analysis. Forty patients with OCD and 25 normal controls were examined using neuropsychological tests including the WAIS-R, WCST, WMS-R, and R-OCFT and functional MRI (fMRI) during the N-back task including 0- and 2-back task. On fMRI, the brain regions activated during the performance and the differences in the activation between patients and controls were identified. Additional analyses of severity and subtypes were conducted by using Y-BOCS severity score, symptom-checklist and Leckman's four-factor model, respectively. On the neuropsychological tests, the OCD patients had significantly lower scores on the delayed recall section of the WMS-R and the immediate recall section of the R-OCFT compared to the controls. On fMRI, the patients showed greater activation in the right dorsolateral prefrontal cortex (DLPFC), left superior temporal gyrus (STG), left insula, and cuneus during two-back task compared to the controls. Right orbitofrontal cortex activity showed a significant positive correlation with Y-BOCS scores in OCD. Furthermore, patients with obsessions/checking rituals (n=10) showed severer memory deficits and decreased activity in the postcentral gyrus than patients with cleanliness/washing rituals (n=14). In conclusion, we found neuropsychological dysfunction and brain abnormalities in OCD. Furthermore, our results suggested that symptom severity and symptom subtype such as obsessions/checking might affect neuropsychological dysfunction and related brain activities.

Neuroimaging in obsessive-compulsive disorder

Many neuroimaging studies have investigated the pathophysiology of obsessive-compulsive disorder. These studies have contributed greatly to the development of contemporary neurocircuitry models of obsessive-compulsive disorder, which emphasize the dysfunction of fronto-striato-thalamocortical circuitry in obsessive-compulsive disorder patients. Specifically, dysfunctions of the orbitofrontal cortex, anterior cingulate cortex, thalamus and caudate nucleus have been revealed through resting state or symptom provocation studies. In addition, dysfunctional activations in the dorsolateral prefrontal cortex and parietal regions have been reported. Recently, these findings have led to the suggestion that the pathogenesis of obsessive-compulsive disorder involves an imbalance between dorsal and ventral fronto-striatal circuits. In this review, we provide updated findings on structural and functional neuroimaging studies performed with obsessive-compulsive disorder patients. The limitations of traditional imaging techniques and recent developments to overcome them will also be discussed.

Subjective idiopathic tinnitus and palliative care: a plan for diagnosis and treatment

This article integrates the highlights of the authors' clinical experiences derived from existing protocols for tinnitus diagnosis and treatment with the evolving discipline of palliation medicine. Specifically, it demonstrates how the inclusion of principles of palliation medicine contributes to the efficacy of treatment.

Association between FDG uptake, CSF biomarkers and cognitive performance in patients with probable Alzheimer's disease

PURPOSE

Brain imaging of FDG uptake and cerebrospinal fluid (CSF) concentration of amyloid-beta 1-42 (Abeta(1-42)) or tau proteins are promising biomarkers in the diagnosis of Alzheimer's disease (AD). There is still uncertainty regarding any association between decreased FDG uptake and alterations in CSF markers.

METHODS

The relationship between FDG uptake, CSF Abeta(1-42) and total tau (T-tau), as well as the Mini-Mental State Examination (MMSE) score was investigated in 34 subjects with probable AD using step-wise linear regression. FDG uptake was scaled to the pons.

RESULTS

Scaled FDG uptake was significantly reduced in the probable AD subjects compared to 17 controls bilaterally in the precuneus/posterior cingulate area, angular gyrus/inferior parietal cortex, inferior temporal/midtemporal cortex, midfrontal cortex, and left caudate. Voxel-based single-subject analysis of the probable AD subjects at p < 0.001 (uncorrected) revealed a total volume of significant hypometabolism ranging from 0 to 452 ml (median 70 ml). The total hypometabolic volume was negatively correlated with the MMSE score, but it was not correlated with the CSF measures. VOI-based step-wise linear regression revealed that scaled FDG uptake in the precuneus/posterior cingulate was negatively correlated with CSF Abeta(1-42). Scaled FDG uptake in the caudate was positively correlated with CSF T-tau.

CONCLUSION

The extent and local severity of the reduction in FDG uptake in probable AD subjects are associated with cognitive impairment. In addition, there appears to be a relationship between local FDG uptake and CSF biomarkers which differs between different brain regions.

Rapid effects of brief intensive cognitive-behavioral therapy on brain glucose metabolism in obsessive-compulsive disorder

Brief intensive cognitive-behavioral therapy (CBT) using exposure and response prevention significantly improves obsessive-compulsive disorder (OCD) symptoms in as little as 4 weeks. However, it has been thought that much longer treatment was needed to produce the changes in brain function seen in neuroimaging studies of OCD. We sought to elucidate the brain mediation of response to brief intensive CBT for OCD and determine whether this treatment could induce functional brain changes previously seen after longer trials of pharmacotherapy or standard CBT. [(18)F]-fluorodeoxyglucose positron emission tomography brain scans were obtained on 10 OCD patients before and after 4 weeks of intensive individual CBT. Twelve normal controls were scanned twice, several weeks apart, without treatment. Regional glucose metabolic changes were compared between groups. OCD symptoms, depression, anxiety and overall functioning improved robustly with treatment. Significant changes in normalized regional glucose metabolism were seen after brief intensive CBT (P=0.04). Compared to controls, OCD patients showed significant bilateral decreases in normalized thalamic metabolism with intensive CBT but had a significant increase in right dorsal anterior cingulate cortex activity that correlated strongly with the degree of improvement in OCD symptoms (P=0.02). The rapid response of OCD to intensive CBT is mediated by a distinct pattern of changes in regional brain function. Reduction of thalamic activity may be a final common pathway for improvement in OCD, but response to intensive CBT may require activation of dorsal anterior cingulate cortex, a region involved in reappraisal and suppression of negative emotions.

Decreased prefrontal, anterior cingulate, insula, and ventral striatal metabolism in medication-free depressed outpatients with bipolar disorder

This study explored whether cerebral metabolic changes seen in treatment resistant and rapid cycling bipolar depression inpatients are also found in an outpatient sample not specifically selected for treatment resistance or rapid cycling. We assessed 15 depressed outpatients with bipolar disorder (six type I and nine type II) who were medication-free for at least 2 weeks and were not predominantly rapid cycling. The average 28-item Hamilton Depression Scale (HAM-D) total score was 33.9. The healthy control group comprised 19 age-matched subjects. All participants received a resting quantitative 18F-fluoro-deoxyglucose positron emission tomography scan. Data analyses were performed with Statistical Parametric Mapping (SPM5). Analyses revealed that depressed patients exhibited similar global metabolism, but decreased absolute regional metabolism in the left much more than right dorsolateral prefrontal cortex, bilateral (left greater than right) insula, bilateral subgenual prefrontal cortex, anterior cingulate, medial prefrontal cortex, ventral striatum, and right precuneus. No region exhibited absolute hypermetabolism. Moreover, HAM-D scores inversely correlated with absolute global metabolism and regional metabolism in the bilateral medial prefrontal gyrus, postcentral gyrus, and middle temporal gyrus. Analysis of relative cerebral metabolism yielded a similar, but less robust pattern of findings. Our findings confirm prefrontal and anterior paralimbic metabolic decreases in cerebral metabolism outside of inpatients specifically selected for treatment resistant and rapid cycling bipolar disorder. Prefrontal metabolic rates were inversely related to severity of depression. There was no evidence of regional hypermetabolism, perhaps because this phenomenon is less robust or more variable than prefrontal hypometabolism.

Selective impairment in visual perception of biological motion in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is associated with a variety of well-documented cognitive deficits such as deficits in memory and executive functioning, but little is known about basic perceptual concomitants of OCD. This study investigated global, configural processing in OCD using dynamic (moving) and static stimuli with minimal demands on cognitive function. Twenty OCD patients and 16 age- and education-matched healthy control subjects were tested on four perceptual tasks: two motion tasks involved detection and discrimination of human activity portrayed by point-light animations ("biological" motion). The other two tasks involved detection of coherent, translational motion defined by random-dot cinematograms and detection of static global shape defined by spatially distributed contours. OCD patients exhibited impaired performance on biological motion tasks; in contrast, their performance on tasks of coherent motion detection and global form perception were comparable to those of healthy controls. These results indicate that OCD patients have a specific deficit in perceiving biological motion signals, whereas their perception of non-biological coherent motion and static global shape is intact. Because efficient social interactions depend on accurate and rapid perception of subtle socially relevant cues, deficits in biological motion perception may compromise social functioning in people with OCD.

Cerebral activation in children and adolescents with obsessive-compulsive disorder before and after treatment: a functional MRI study

BACKGROUND

Structural and functional fronto-striatal abnormalities are involved in the pathophysiology of obsessive-compulsive disorder (OCD). The aims of the present study were: (a) to investigate possible regional brain dysfunction in premotor cortico-striatal activity in drug-naïve children and adolescents with OCD; (b) to correlate brain activation with severity of obsessive-compulsive symptomatology; and (c) to detect possible changes in brain activity after pharmacological treatment.

METHOD

Twelve children and adolescents (age range 7-18 years; seven male, five female) with DSM-IV obsessive-compulsive disorder and twelve healthy subjects matched for age, sex and intellectual level were studied. Functional magnetic resonance imaging data were obtained during the performance of simple and complex sequences.

RESULTS

Comparing the complex motor condition with the simple control condition, both patients and controls showed a pattern of cerebral activation involving the fronto-parietal cortex and basal ganglia. Compared with controls, OCD patients presented significantly higher brain activation bilaterally in the middle frontal gyrus. After 6 months of pharmacological treatment and with clear clinical improvement, activation in the left insula and left putamen decreased significantly.

CONCLUSION

In a paediatric OCD sample that was treatment naïve and without another psychiatric disorder we showed hyperactivation of the circuits that mediate symptomatic expression of OCD. The cerebral activation decreases after treatment and clinical improvement.

Functional MRI study of brain activation alterations in patients with obsessive-compulsive disorder after symptom improvement

Dysfunction of the frontal-subcortical circuits has been the most common finding in the pathophysiology of obsessive-compulsive disorder (OCD), and recent neuropsychological studies have shown cognitive impairments in OCD. To clarify the pathophysiology of OCD without the confounding effects of medication, we investigated the alterations of brain function in OCD patients and changes after clinical improvement due solely to behavior therapy. The participants were 11 outpatients with OCD and 19 normal controls. The patients received 12 weeks of behavior therapy. We investigated the differences in the behavioral performance and functional magnetic resonance imaging results during the Stroop test in the patients and normal controls, and their changes after treatment in the patients. The patients showed less activation in the anterior cingulate gyrus and cerebellum than control subjects. Following significant improvement in OC symptoms, the cerebellum and parietal lobe showed increased activation, and the orbitofrontal cortex, middle frontal gyrus, and temporal regions showed decreased activation during the Stroop task, and performance of the task itself improved. Our findings suggest that dysfunction of the posterior brain regions, especially the cerebellum, is involved in the pathogenesis of OCD, and that normalization in function can occur with improvement of OC symptoms.

New onset obsessive-compulsive symptoms in children and adolescents with severe traumatic brain injury

Traumatic brain injury (TBI) constitutes a major source of psychiatric morbidity and disability. This study examines new onset of obsessions and compulsions (OCS) within 1 year of severe pediatric TBI. Eighty children and adolescents ages 6-18 years with severe TBI were interviewed by a child psychiatrist using the Diagnostic Interview for Children and Adolescents-Revised to diagnose OCS and comorbidities. A brain magnetic resonance imaging used a 1.5 T scanner 3 months after injury with a T1-weighted spoiled gradient-recalled-echo sequence to provide high spatial resolution and T1- and T2(*)-contrast sensitivity. Race, sex, socioeconomic status, psychosocial adversity, and injury severity were used to predict new onset OCS. Psychiatric comorbidities and brain lesion volumes in orbitofrontal, mesial prefrontal, temporal lobe, basal ganglia, and thalamus were examined in relation to new onset OCS. Twenty-one children (21/72, 29.2%) had OCS after TBI. Most common were worries about disease, cleanliness, and inappropriate actions as well as excessive cleaning, doing things a certain way and ordering. Anxiety disorders, mania, dysthymia, depressive symptoms, and posttraumatic stress disorder were significantly associated with new onset OCS. Injury severity was not associated with new onset OCS. Greater psychosocial adversity (P=0.009), and being female (P=0.005) were associated with OCS while mesial prefrontal and temporal lobe lesions were associated with new onset obsessions (P<0.05). OCS are common after severe pediatric TBI and are associated with greater comorbidities. New onset obsessions are associated with female sex, psychosocial adversity, and mesial prefrontal and temporal lesions.

Applying neuroimaging ligands to study major depressive disorder

The recent increase in radioligands available for neuroimaging major depressive disorder has led to advancements in our understanding of the pathophysiology of this illness and improved antidepressant development. Major depressive disorder can be defined as an illness of recurrent major depressive episodes of persistently low mood, dysregulated sleep, appetite and weight, anhedonia, cognitive impairment, and suicidality. The main target sites investigated with radioligand neuroimaging include receptor sites that regulate in response to lowered monoamine levels, targets related to removal of monoamines, uptake of ligands related to regional brain function, and target sites of antidepressants.

What every psychiatrist should know about PANDAS: a review

The term Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcus infections (PANDAS) was coined by Swedo et al. in 1998 to describe a subset of childhood obsessive-compulsive disorders (OCD) and tic disorders triggered by group-A beta-hemolytic Streptococcus pyogenes infection. Like adult OCD, PANDAS is associated with basal ganglia dysfunction. Other putative pathogenetic mechanisms of PANDAS include molecular mimicry and autoimmune-mediated altered neuronal signaling, involving calcium-calmodulin dependent protein (CaM) kinase II activity. Nonetheless the contrasting results from numerous studies provide no consensus on whether PANDAS should be considered as a specific nosological entity or simply a useful research framework. Herein we discuss available data that could provide insight into pathophysiology of adult OCD, or might explain cases of treatment-resistance. We also review the latest research findings on diagnostic and treatment.

Electrophysiological evidence for cortical abnormalities in obsessive-compulsive disorder - a replication study using auditory event-related P300 subcomponents

Neuroimaging studies in recent years suggest that cortical hyperactivity associated with more aroused cognitive processes and overfocussed attention is involved in the pathogenesis of obsessive-compulsive disorder (OCD), which was electrophysiologically supported by an own pilot-study in a small sample of stabilized OCD patients. To replicate this first finding, the hypothesis of cortical hyperactivity was studied by measuring auditory event-related P300 subcomponents, especially the amplitude of the P3a and P3b subcomponent, in a large sample of acutely ill and unmedicated patients with OCD. The P300 of 63 patients with OCD (30 males, 33 females, 33.7+/-10.2 years old; 25.4+/-5.4 points at Yale-Brown-Obsessive-Compulsive-Scale (Y-BOCS)) was separated with dipole source analysis (BESA) into their subcomponents P3a and P3b, and compared to the P300 subcomponents of 63 gender and age matched healthy controls. No difference in the amplitude of P3a was found, but OCD patients had significantly larger amplitudes of P3b than the healthy controls, which replicates the results of the pilot study. Once again, our findings point to a hyperactivated cortical state also of temporo-parietal and hippocampal regions in OCD.

Corpus callosum in patients with obsessive-compulsive disorder: diffusion-tensor imaging study

PURPOSE

To prospectively examine microstructural white matter abnormalities in the corpus callosum (CC) of patients with obsessive-compulsive disorder (OCD), as compared with control subjects, and to investigate the relationship between diffusion-tensor (DT) imaging measures of the CC region and clinical symptoms of OCD.

MATERIALS AND METHODS

Institutional review board approval was obtained, and each participant--or the participant's parent(s)--provided written informed consent. Sixteen patients with OCD (seven male, nine female; mean age, 28.7 years +/- 9.8 [standard deviation]) and 16 matched healthy volunteers (control subjects) (seven male, nine female; mean age, 29.9 years +/- 9.0) were examined. Mean diffusivity and fractional anisotropy (FA) were measured in five subdivisions of the CC. The paired t test was performed to compare the mean diffusivity or the FA in CC regions between the patients with OCD and the control subjects.

RESULTS

There were no significant differences (rostrum, P = .15; genu, P = .88; rostral body, P = .12; isthmus, P = .77; splenium, P = .88) in mean diffusivity between the patients with OCD and the healthy volunteers. A significant reduction in FA was observed in the rostrum of the CC in patients with OCD compared with the rostral FA in the control subjects (P < .001). Higher FA in only the rostrum correlated significantly with lower Yale-Brown obsessive-compulsive scale score (r = -0.72, P = .002).

CONCLUSION

Study results support the widely held view that the orbital prefrontal region is involved in the pathophysiology of OCD and indicate that the orbitofrontal circuit influences symptom severity in patients with OCD.

Motor inhibition in trichotillomania and obsessive-compulsive disorder

We investigated motor inhibition abilities in trichotillomania (TTM) and obsessive-compulsive disorder (OCD), two disorders characterized by repetitive, intentionally performed behaviors. Performance in a GoNogo experiment of 25 TTM and 21 OCD participants was compared to the performance of 26 HC participants. In contrast to OCD and HC participants, TTM participants tended to perform either 'fast and inaccurate' (indicating poor motor inhibition) or 'slow and accurate'. TTM participants with poor motor inhibition reported a significantly earlier age of TTM onset than those TTM participants who performed well. There was no evidence for motor inhibition deficits in OCD. Based on our data, a subgroup of TTM sufferers seems to be characterized by motor inhibition deficits.

Glutamatergic Synaptic Dysfunction and Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is a debilitating neuropsychiatric condition estimated to afflict 1-3% of the world population. The estimated financial impact in the treatment and management of OCD is in the billions of dollars annually in the US alone. At present there is a marked lack of evidence on the specific causes of OCD. Current hypotheses largely focus on the serotonin (5-HT) system on the basis of the effectiveness of selective serotonin reuptake inhibitors (SSRIs) in alleviating symptoms of patients with OCD, yet a considerable fraction of patients are non-responsive or minimally responsive to these agents. Despite this fact, SSRIs have remained the primary pharmacological treatment avenue for OCD. In recent years, multiple lines of evidence have implicated glutamatergic synaptic dysfunction within the cortico-striatal-thalamo-cortical (CSTC) brain circuit in the etiology of OCD and related disorders, thereby prompting intensified effort in the development and evaluation of agents that modulate glutamatergic neurotransmission for the treatment of OCD. With this in mind, here we review the following topics with respect to synaptic dysfunction and the neural circuitry underlying OCD: (1) evidence supporting the critical involvement of the CSTC circuit, (2) genetic studies supporting the involvement of glutamatergic dysfunction, (3) insights from genetic animal models of OCD, and (4) preliminary findings with glutamatergic neurotransmission-modulating agents in the treatment of OCD. Given the putative mechanistic overlap between OCD and the broader OC-spectrum of disorders, unraveling the synaptic basis of OCD has potential to translate into more effective treatments for an array of poorly understood human disorders.

A psychological and neuroanatomical model of obsessive-compulsive disorder

Imaging, surgical, and lesion studies suggest that the prefrontal cortex (orbitofrontal and anterior cingulate cortexes), basal ganglia, and thalamus are involved in the pathogenesis of obsessive-compulsive disorder (OCD). On the basis of these findings several models of OCD have been developed, but have had difficulty fully integrating the psychological and neuroanatomical findings of OCD. Recent research in the field of cognitive neuroscience on the normal function of these brain areas demonstrates the role of the orbitofrontal cortex in reward, the anterior cingulate cortex in error detection, the basal ganglia in affecting the threshold for activation of motor and behavioral programs, and the prefrontal cortex in storing memories of behavioral sequences (called "structured event complexes" or SECs). The authors propose that the initiation of these SECs can be accompanied by anxiety that is relieved with completion of the SEC, and that a deficit in this process could be responsible for many of the symptoms of OCD. Specifically, the anxiety can form the basis of an obsession, and a compulsion can be an attempt to receive relief from the anxiety by repeating parts of, or an entire, SEC. The authors discuss empiric support for, and specific experimental predictions of, this model. The authors believe that this model explains the specific symptoms, and integrates the psychology and neuroanatomy of OCD better than previous models.

Dopamine transporter density in the basal ganglia in obsessive-compulsive disorder, measured with [123I]IPT SPECT before and after treatment with serotonin reuptake inhibitors

It has been suggested that dopamine as well as serotonin are associated with the pathophysiology of obsessive-compulsive disorder (OCD). 5-Hydroxytryptophan inhibits dopamine release in healthy persons as well as in patients with OCD, and serotonin tonic inhibition affects dopamine function in basal ganglia, indicating a close relationship between serotonin and the dopamine system. Using iodine-123-labeled N-(3-iodopropen-2-yl)-2 beta-carbomethoxy-3beta-(4-chlorophenyl) tropane ([(123)I]IPT) single photon emission computed tomography (SPECT), we investigated the dopamine transporter (DAT) density in the basal ganglia of patients with OCD. The test consists of two measurements before and after treatment with serotonin reuptake inhibitors (SRIs). Ten patients with OCD before and after treatment with SRIs were included. We performed brain SPECT 2 h after intravenous administration of [(123)I]IPT using a dual-head SPECT camera (Vertex, ADAC, Calif., USA) and analyzed the SPECT data, reconstructed for the assessment of the specific/nonspecific DAT binding ratio in the basal ganglia. We then examined the correlation between the scores of OCD symptom changes, assessed with the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), and DAT binding ratio. Patients with OCD after treatment with SRIs showed a significantly decreased DAT binding ratio in the right basal ganglia compared with baseline. A significant correlation was found between the total scores and compulsion score changes of the Y-BOCS and the changes of the DAT binding ratio of the right basal ganglia. These findings suggest that the dopaminergic neurotransmitter system of the basal ganglia could play an important role in the symptom improvement of OCD patients.

Neurocognitive endophenotypes of obsessive-compulsive disorder

Endophenotypes (intermediate phenotypes) are objective, heritable, quantitative traits hypothesized to represent genetic risk for polygenic disorders at more biologically tractable levels than distal behavioural and clinical phenotypes. It is theorized that endophenotype models of disease will help to clarify both diagnostic classification and aetiological understanding of complex brain disorders such as obsessive-compulsive disorder (OCD). To investigate endophenotypes in OCD, we measured brain structure using magnetic resonance imaging (MRI), and behavioural performance on a response inhibition task (Stop-Signal) in 31 OCD patients, 31 of their unaffected first-degree relatives, and 31 unrelated matched controls. Both patients and relatives had delayed response inhibition on the Stop-Signal task compared with healthy controls. We used a multivoxel analysis method (partial least squares) to identify large-scale brain systems in which anatomical variation was associated with variation in performance on the response inhibition task. Behavioural impairment on the Stop-Signal task, occurring predominantly in patients and relatives, was significantly associated with reduced grey matter in orbitofrontal and right inferior frontal regions and increased grey matter in cingulate, parietal and striatal regions. A novel permutation test indicated significant familial effects on variation of the MRI markers of inhibitory processing, supporting the candidacy of these brain structural systems as endophenotypes of OCD. In summary, structural variation in large-scale brain systems related to motor inhibitory control may mediate genetic risk for OCD, representing the first evidence for a neurocognitive endophenotype of OCD.

Dissociation between MEG alpha modulation and performance accuracy on visual working memory task in obsessive compulsive disorder

Oscillatory brain activity in the alpha band (8-13 Hz) is modulated by cognitive events. Such modulation is reflected in a decrease of alpha (event-related desynchronization; ERD) with high cognitive load, or an increase (event-related synchronization) with low cognitive demand or with active inhibition of distractors. We used magnetoencephalography to investigate the pattern of prefrontal and parieto-occipital alpha modulation related to two variants of visual working memory task (delayed matching-to-sample) with and without a distractor. We tested nonmedicated, nondepressed patients suffering obsessive-compulsive disorder (OCD), and pair-matched healthy controls. The level of event-related alpha as a function of time was estimated using the temporal-spectral evolution technique. The results in OCD patients indicated: (1) a lower level of prestimulus (reference) alpha when compared to controls, (2) a task-phase specific reduction in event-related alpha ERD in particular for delayed matching-to-sample task with distractor, (3) no significant correlations between the pattern of modulation in prefrontal and parietal-occipital alpha oscillatory activity. Despite showing an abnormally low alpha modulation, the OCD patients' performance accuracy was normal. The results suggest a relationship of alpha oscillations and the underlying thalamocortical network to etiology of OCD and an involvement of a compensatory mechanism related to effortful inhibition of extrinsic and intrinsic interference.

Repetitive transcranial magnetic stimulation for the treatment of obsessive compulsive disorder: a double-blind controlled investigation

BACKGROUND

To determine the efficacy and tolerability of repetitive transcranial magnetic stimulation (rTMS) as a treatment for obsessive compulsive disorder (OCD) in a double-blind placebo-controlled study.

METHOD

Subjects with treatment-resistant OCD were randomized to rTMS (n = 10) or sham rTMS (n = 8) for 10 sessions of daily stimulation over the left dorsolateral prefrontal cortex (DLPFC), with subjects and raters being blind to the treatment. Subjects were offered an open extension of up to 20 sessions of rTMS.

RESULTS

The two groups did not differ on change in Yale-Brown Obsessive Compulsive Scale (YBOCS) or Maudsley Obsessive-Compulsive Inventory scores over 10 sessions, with or without correction for depression ratings. Over 20 sessions, there was a significant reduction in total YBOCS scores, but not after controlling for depression. rTMS over 20 sessions was well tolerated.

CONCLUSION

Two weeks of rTMS over the left DLPFC is ineffective for treatment-resistant OCD.

The differential impact of executive attention dysfunction on episodic memory in obsessive-compulsive disorder patients with checking symptoms vs. those with washing symptoms

Neuropsychological studies of obsessive-compulsive disorder (OCD) have pointed to memory and attention deficits among its sufferers, but these reports have largely ignored the possibility that cognitive disturbances may vary across OCD clinical subtypes, or that their interactions may differ between subtypes. The purpose of the present study was to determine whether "checkers" and "washers" demonstrate differences in their memory and executive attention function. Fifty-three outpatients with primary DSM-IV diagnosis of OCD with typical checking (n=27) or washing (n=26) rituals participated in the study. Patients were administered the Wechsler Memory Scale-Revised and a comprehensive neuropsychological battery to assess executive attention function. Various neuropsychological tests were then subjected to factor analysis. Neuropsychological test results and obtained factor scores were compared between "washers" and "checkers". Effects of these factor scores on memory by OCD subtypes were examined. No significant difference in terms of demographic and clinical variables was found between the two groups. Checkers displayed performance deficits on Stroop test, Trail Making Test, GO/NO GO test (commission errors) and category fluency. Three factors, inhibition, cognitive flexibility, and multi-tasking, were obtained. Statistically significant differences were observed between the two groups on the inhibition and the cognitive flexibility scores, but not on the general memory or the multi-tasking score. There was a statistically significant interaction between groups and the inhibition score. Only among "checkers", a significant correlation was noted between the inhibition factor and the general memory, while no such correlation was observed among "washers". Among "checkers", poor general memory was related to inhibition deficits.

Cortical thinning in obsessive compulsive disorder

Although studies of obsessive-compulsive disorder (OCD) over the last 20 years have suggested abnormalities in frontal-subcortical circuitry, evidences of structural abnormalities in those areas are still imperfect and contradictory. With recent advances in neuroimaging technology, it is now possible to study cortical thickness based on cortical surfaces, which offers a direct quantitative index of cortical mass. Using the constrained Laplacian-based automated segmentation with proximities (CLASP) algorithm, we measured cortical thickness of 55 patients with OCD (33 men and 22 women) and 52 age- and sex-matched healthy volunteers (32 men and 20 women). We found multiple regions of cortical thinning in OCD patients compared to the normal control group. Patients with OCD had thinner left inferior frontal, left middle frontal, left precentral, left superior temporal, left parahippocampal, left orbitofrontal, and left lingual cortices. Most thinned regions were located in the left ventral cortex system, providing a new perspective that this ventral cortical system may be involved in the pathophysiology of OCD.

Integrating evidence from neuroimaging and neuropsychological studies of obsessive-compulsive disorder: the orbitofronto-striatal model revisited

Obsessive-compulsive disorder (OCD) is a common, heritable and disabling neuropsychiatric disorder. Theoretical models suggest that OCD is underpinned by functional and structural abnormalities in orbitofronto-striatal circuits. Evidence from cognitive and neuroimaging studies (functional and structural magnetic resonance imaging (MRI) and positron emission tomography (PET)) have generally been taken to be supportive of these theoretical models; however, results from these studies have not been entirely congruent with each other. With the advent of whole brain-based structural imaging techniques, such as voxel-based morphometry and multivoxel analyses, we consider it timely to assess neuroimaging findings to date, and to examine their compatibility with cognitive studies and orbitofronto-striatal models. As part of this assessment, we performed a quantitative, voxel-level meta-analysis of functional MRI findings, which revealed consistent abnormalities in orbitofronto-striatal and other additional areas in OCD. This review also considers the evidence for involvement of other brain areas outside orbitofronto-striatal regions in OCD, the limitations of current imaging techniques, and how future developments in imaging may aid our understanding of OCD.

Event-related functional magnetic resonance imaging of response inhibition in obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) has been hypothesized to involve inhibitory control dysfunction related to abnormal frontal-striatal-thalamic-cortical (FSTC) circuitry.

METHODS

We examined the neural substrates of response inhibition in adults with OCD using functional magnetic resonance imaging (fMRI) and a go/no-go task. Participants consisted of 12 adults with OCD and 14 healthy comparison subjects.

RESULTS

During response inhibition, healthy adults showed predominantly right-hemisphere activation including the right inferior frontal gyrus, whereas the patient group showed a more diffuse, bilateral pattern of activation. Furthermore, the OCD group demonstrated less activation than the comparison group in several right-hemisphere regions during response inhibition, including inferior and medial frontal gyri. Symptom severity was inversely correlated with activation in right orbitofrontal and anterior cingulate gyri and positively correlated with thalamic and posterior cortical activations. Neither depressed mood nor medication status could account for the results.

CONCLUSIONS

These findings indicate that adults with OCD demonstrate underactivation of FSTC circuitry during response inhibition. Results suggest that the thalamus and related circuitry may play a role in the expression or intensity of OCD symptoms, whereas right frontal subregions may be involved in the suppression of symptoms.

White matter abnormalities in drug-naïve patients with obsessive-compulsive disorder: a diffusion tensor study before and after citalopram treatment

OBJECTIVE

The aim was to investigate the white matter abnormalities of drug-naïve patients with obsessive-compulsive disorder (OCD) using diffusion tensor-imaging and the white matter changes in the patients after pharmacotherapy.

METHOD

Thirteen drug-naïve OCD patients and 13 age- and sex-matched healthy comparison subjects were examined using diffusion tensor-imaging and structural magnetic resonance imaging. Measurements were made in OCD patients before and after 12 weeks of citalopram treatment.

RESULTS

Compared with controls, the drug-naïve OCD patients showed significant increases in fractional anisotropy (FA) in the corpus callosum, the internal capsule and white matter in the area superolateral to the right caudate. The increases in FA were mostly no longer observed in patients after 12 weeks of treatment compared with controls.

CONCLUSION

Our findings suggest that white matter alterations are associated with the pathophysiology of OCD, and the abnormalities may be partly reversible with pharmacotherapy.