A brain single photon-emission computed tomography (SPECT) study of generalized social phobia

Resting regional brain metabolism in social anxiety disorder and the effect of moclobemide therapy

While there is mounting evidence of abnormal reactivity of several brain regions in social anxiety disorder, and disrupted functional connectivity between these regions at rest, relatively little is known regarding resting regional neural activity in these structures, or how such activity is affected by pharmacotherapy. Using 2-deoxy-2-(F-18)fluoro-D-glucose positron emission tomography, we compared resting regional brain metabolism between SAD and healthy control groups; and in SAD participants before and after moclobemide therapy. Voxel-based analyses were confined to a predefined search volume. A second, exploratory whole-brain analysis was conducted using a more liberal statistical threshold. Fifteen SAD participants and fifteen matched controls were included in the group comparison. A subgroup of SAD participants (n = 11) was included in the therapy effect comparison. No significant clusters were identified in the primary analysis. In the exploratory analysis, the SAD group exhibited increased metabolism in left fusiform gyrus and right temporal pole. After therapy, SAD participants exhibited reductions in regional metabolism in a medial dorsal prefrontal region and increases in right caudate, right insula and left postcentral gyrus. This study adds to the limited existing work on resting regional brain activity in SAD and the effects of therapy. The negative results of our primary analysis suggest that resting regional activity differences in the disorder, and moclobemide effects on regional metabolism, if present, are small. While the outcomes of our secondary analysis should be interpreted with caution, they may contribute to formulating future hypotheses or in pooled analyses.

Imaging and Genetic Approaches to Inform Biomarkers for Anxiety Disorders, Obsessive-Compulsive Disorders, and PSTD

Anxiety disorders are the most common mental health problem in the world and also claim the highest health care cost among various neuropsychiatric disorders. Anxiety disorders have a chronic and recurrent course and cause significantly negative impacts on patients' social, personal, and occupational functioning as well as quality of life. Despite their high prevalence rates, anxiety disorders have often been under-diagnosed or misdiagnosed, and consequently under-treated. Even with the correct diagnosis, anxiety disorders are known to be difficult to treat successfully. In order to implement better strategies in diagnosis, prognosis, treatment decision, and early prevention for anxiety disorders, tremendous efforts have been put into studies using genetic and neuroimaging techniques to advance our understandings of the underlying biological mechanisms. In addition to anxiety disorders including panic disorder, generalised anxiety disorder (GAD), specific phobias, social anxiety disorders (SAD), due to overlapping symptom dimensions, obsessive-compulsive disorder (OCD), and post-traumatic stress disorder (PTSD) (which were removed from the anxiety disorder category in DSM-5 to become separate categories) are also included for review of relevant genetic and neuroimaging findings. Although the number of genetic or neuroimaging studies focusing on anxiety disorders is relatively small compare to other psychiatric disorders such as psychotic disorders or mood disorders, various structural abnormalities in the grey or white matter, functional alterations of activity during resting-state or task conditions, molecular changes of neurotransmitter receptors or transporters, and genetic associations have all been reported. With continuing effort, further genetic and neuroimaging research may potentially lead to clinically useful biomarkers for the prevention, diagnosis, and management of these disorders.

Biological markers for anxiety disorders, OCD and PTSD - a consensus statement. Part I: Neuroimaging and genetics

OBJECTIVES

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part I) summarises findings on potential biomarkers in neuroimaging studies, including structural brain morphology, functional magnetic resonance imaging and techniques for measuring metabolic changes, including positron emission tomography and others. Furthermore, this review reports on the clinical and molecular genetic findings of family, twin, linkage, association and genome-wide association studies. Part II of the review focuses on neurochemistry, neurophysiology and neurocognition.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high-quality research has accumulated that will improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

Neuroimaging in social anxiety disorder: a systematic review of the literature

Brain imaging techniques allow the in vivo evaluation of the human brain, leading to a better understanding of its anatomical, functional and metabolic substrate. The aim of this current report is to present a systematic and critical review of neuroimaging findings in Social Anxiety Disorder (SAD). A literature review was performed in the PubMed Medline, Scielo and Web of Science databases using the following keywords: 'MRI', 'functional', 'tomography', 'PET', 'SPECT', 'spectroscopy', 'relaxometry', 'tractography' and 'voxel' crossed one by one with the terms 'social anxiety' and 'social phobic', with no limit of time. We selected 196 articles and 48 of them were included in our review. Most of the included studies have explored the neural response to facial expressions of emotion, symptoms provocation paradigms, and disorder-related abnormalities in dopamine or serotonin neurotransmission. The most coherent finding among the brain imaging techniques reflects increased activity in limbic and paralimbic regions in SAD. The predominance of evidence implicating the amygdala strengthens the notion that it plays a crucial role in the pathophysiology of SAD. The observation of alterations in pre-frontal regions and the reduced activity observed in striatal and parietal areas show that much remains to be investigated within the complexity of SAD. Interesting, follow-up designed studies observed a decrease in perfusion in these same areas after either by pharmacological or psychological treatment. The medial prefrontal cortex provided additional support for a corticolimbic model of SAD pathophysiology, being a promising area to investigation. Furthermore, the dopaminergic and GABAergic hypotheses seem directed related to its physiopathology. The present review indicates that neuroimaging has contributed to a better understanding of the neurobiology of SAD. Although there were several methodological differences among the studies, the global results have often been consistent, reinforcing the evidence of a specific cerebral circuit involved in SAD, formed by limbic and cortical areas.

Neuroimaging in anxiety disorders

Neuroimaging studies have gained increasing importance in validating neurobiological network hypotheses for anxiety disorders. Functional imaging procedures and radioligand binding studies in healthy subjects and in patients with anxiety disorders provide growing evidence of the existence of a complex anxiety network, including limbic, brainstem, temporal, and prefrontal cortical regions. Obviously, "normal anxiety" does not equal "pathological anxiety" although many phenomena are evident in healthy subjects, however to a lower extent. Differential effects of distinct brain regions and lateralization phenomena in different anxiety disorders are mentioned. An overview of neuroimaging investigations in anxiety disorders is given after a brief summary of results from healthy volunteers. Concluding implications for future research are made by the authors.

Resting brain perfusion in social anxiety disorder: a voxel-wise whole brain comparison with healthy control subjects

INTRODUCTION

Social anxiety disorder (SAD) is a condition characterised by fears of social interaction and performance situations. SAD may be related to a dysregulation or hyperactivity of cortico-limbic circuitry. This is the first voxel-based whole brain study comparing resting function in SAD to a normal control group.

METHODS

Resting perfusion in adult subjects with generalised SAD was compared with healthy adult volunteers using Statistical Parametric Mapping (SPM). In subjects with SAD, correlations were also sought between resting perfusion and clinical severity measured using the total Liebowitz Social Anxiety Scale (LSAS).

RESULTS

Twenty-eight subjects with SAD were compared with 19 healthy volunteers. SAD subjects had increased resting perfusion in the frontal cortex and right cerebellum, and decreased perfusion in the pons, left cerebellum, and right precuneus. Total LSAS correlated positively with left frontal cortex resting perfusion, and negatively with right fusiform and right lingual perfusion.

CONCLUSION

This study demonstrated increased resting frontal function in social anxiety disorder that is consistent with its hypothesised role in the modulation of excessive limbic activity in anxiety disorders. The correlation of posterior cortical resting function with the severity of SAD symptoms may point to defective perception of self and others.

A comparison of the effects of citalopram and moclobemide on resting brain perfusion in social anxiety disorder

INTRODUCTION

The serotonin specific reuptake inhibitor (SSRI) citalopram and the reversible mono-amine oxidase-A inhibitor (RIMA) moclobemide have both been used successfully for the treatment of social anxiety disorder (SAD). In this study we investigate the effects of these compounds on resting brain function using single photon emission computed tomography (SPECT).

METHODS

Subjects meeting DSM-IV criteria for SAD underwent regional cerebral blood flow (rCBF) SPECT using Tc-HMPAO at baseline and after 8 weeks of treatment with either citalopram or moclobemide. Using statistical parametric mapping brain SPECT studies were analysed to determine the effects of treatment on rCBF, to compare the effects of citalopram and moclobemide, and to detect correlations between changes in rCBF and clinical response.

RESULTS

Subjects received citalopram (n=17) or moclobemide (n=14) as therapy. Subjects in both treatment groups demonstrated a significant improvement of SAD symptoms as measured by the Liebowitz Social Anxiety Scale total score. All subjects demonstrated a decrease in rCBF in the insulae post therapy. Subjects receiving citalopram had decreased superior cingulate rCBF after therapy compared to those receiving moclobemide.

CONCLUSION

Both SSRI's and RIMA's decreased rCBF in the insulae during treatment of SAD; an effect that may be consistent with the role of these regions in processing internal somatic cues evoked by emotional stimuli. Citalopram had a greater effect on superior cingulate perfusion, an effect that is consistent with evidence of high levels of 5-HT transporters in this region.

Why do some individuals develop social phobia? A review with emphasis on the neurobiological influences

Social phobia, or social anxiety disorder, is now considered the most common anxiety disorder. Still, the etiology of the disorder is to an essential degree unknown. This paper presents an overview of various pathways to be considered in relation to the development of social phobia. The literature concerning genetics and family aggregation, behavioral inhibition, various forms of the learning account, and neurobiological influences was examined. The reviewed studies suggest that social phobia has a neuroanatomical basis in a highly sensitive fear network centered in the amygdaloid-hippocampal region, i.e. "the alarm system" of the brain, and encompassing the prefrontal cortex. This pattern is congruent with genetic studies proposing that the genetic component comprises a general vulnerability to fearfulness rather than to social phobia itself. Further, both family and twin studies support a hereditary contribution to social phobia resulting from genetic and environmental factors, which most likely operate in an interactive way rather than acting in isolation.

Neurocircuitry of anxiety disorders

A major focus in the field of anxiety in the past decade, and an area of intense ongoing interest, is the delineation of the basic neurocircuitry underlying normal and pathologic anxiety. Preclinical work defining the basic neurocircuitry responsible for fear responding has fueled neuroimaging investigations attempting to model the neurocircuitry of the anxiety disorders. Herewith, the authors review neuroimaging findings contributing to the development and refinement of neuroanatomic models for post-traumatic stress disorder, panic disorder, and social anxiety disorder.

Impaired conditional discrimination learning in social phobia

Eyelid conditional discrimination learning (ECDL) is a test of discriminative aversive conditioning. It places minimal demands on motivation and was shown to selectively test temporal lobe function. Twenty-five unmedicated social phobia (SP) patients (mean age 29.5 +/- 7.0 years), diagnosed according to DSM-IV criteria, and 25 age- and gender-matched healthy controls (HC, mean age 34.0 +/- 8.6 years) were examined with an ECDL paradigm. In the experiment two differently colored stimuli are randomly presented. Only one of the stimuli (reinforced trial) is followed by an aversive airpuff to the cornea, as opposed to unreinforced trials not followed by an airpuff. Conditioned responses (CRs) consist of reflex eyelid closures already upon light presentation. HC as well as SP patients showed a significant difference between reinforced and unreinforced trials. In SP patients, CR frequency did not increase during the ECDL task, while HCs showed appropriate conditional discrimination ability. Thus the results indicate an impairment of adequate behavior modification in an aversive conditioning task in SP.

Neuroimaging studies of amygdala function in anxiety disorders

Neuroimaging research has helped to advance neurobiological models of anxiety disorders. The amygdala is known to play an important role in normal fear conditioning and is implicated in the pathophysiology of anxiety disorders. The amygdala may also be a target for the beneficial effects of cognitive-behavioral and medication treatments for anxiety disorders. In the current paper, we review neuroimaging research pertaining to the role of the amygdala in anxiety disorders and their treatment. Moreover, we discuss the development of new neuroimaging paradigms for measuring aspects of amygdala function, as well as the function of related brain regions. We conclude that such tools hold great promise for facilitating progress in relevant basic neuroscience as well as clinical research domains.

Brain function in social anxiety disorder

What have these studies revealed about SAD? First, few studies have been performed so far, with even fewer replications. Most of the work has been exploratory in nature and follows the paradigms used in PD. This approach has been justifiably criticized. The use of psychological (naturalistic) challenges may be more appropriate in SP than chemical challenges. The paradigms of public speaking, autobiographical scripts, or similar behavioral challenges merit further use, exploration, and validation if symptoms resembling those of the condition proper are to be induced in experimental circumstances. However, some tentative conclusions can be drawn from the research performed so far. There is no enough evidence to support the presence of structural brain abnormality in SAD. Admittedly, such a finding would have been very unlikely. On the other hand, evidence of subtle functional abnormalities is accumulating. On the nosologic question, there appear to be differences from PD. While in some challenges (e.g., CO2 and pentagastrin) the two conditions differ only in degree, in others (e.g., lactate, caffeine, and flumazenil), the separation is clearer. Equally, there is a strong argument to differentiate the generalized from the specific form of social anxiety on the basis of substantial (albeit accidental) findings outlined earlier. More sophisticated neuroimaging techniques, directly comparing patients from both groups before and after pharmacologic or psychological treatment, should provide more conclusive evidence on this issue. What might also help future research is the integration of biological investigations with specific personality profiles. In one study, SAD patients scored low in novelty seeking, self-directedness and cooperativeness and high in harm avoidance. It has been hypothesized that such results indicate serotonergic and dopaminergic dysregulation, which is consistent with the findings described earlier. The best evidence for neurotransmitter abnormality so far is for altered dopamine function at the level of the basal ganglia, either pre- or postsynaptic, which may result in reduced basal ganglia function so that the normal fluidity of social motor functions (e.g., smiling, eye movements, and speech) are impaired, thus leading to the cognitive symptoms of social anxiety and the subsequent generation of avoidance behavior. Such patients should respond poorly to antipsychotics, and additional challenges with these drugs could be used to test this theory. Furthermore, more research needs to be done to elucidate the mechanism by which SSRIs work in SAD. Neuroanatomical models of social anxiety (Fig. 4) [see structure: Text], explaining the site of action of drugs and psychological treatments, have been proposed in recent years. Central to these models is the notion of an innate anxiety circuit, which could be tentatively identified with the behavioral inhibition system, the septohippocampal system. This area receives 5-HT, NE, and dopamine input and has connections with the cortex and limbic structures. The relevance of these models remains to be assessed in experiments that are specifically designed to test them.

Social anxiety disorder

In 1990s, it was found that GSAD is more common, more disabling, and more chronic than previously realized. For the first time, there are good data about a range of effective treatment options that can offer these patients substantial relief and protection from their disability.

The quest for biological correlates of social phobia: an interim assessment

OBJECTIVE

The primary goal of this review was to assess critically the literature concerning the ongoing search for possible biological correlates of social phobia.

METHODS

In addition to manual searches, Medline, Current Contents and Psych Info databases were searched for relevant publications.

RESULTS

On the evidence of an extensive body of research, so far biological correlates of social phobia remain elusive. Furthermore, the majority of studies reveal by default that the neurobiological functioning of social phobics is very much like that of normal control subjects.

CONCLUSION

The conceptual and methodological foundations underpinning the current research programme are discussed critically. Its main weaknesses were found to be: lack of theory to guide research and aid the interpretation of results, static comparisons between subject groups and analysis oblivious to great individual variations. Possibilities of alternative approaches to study the neurobiology of social phobia are raised. Among others, continuous and situation-specific measurement, subjects used as their own controls and neurobiological correlates of clinical improvement following psychotherapy are considered.

Drugs in development for social anxiety disorder: more to social anxiety than meets the SSRI

Individuals with social phobia (SP) fear and avoid a wide variety of social and performance situations in which they are exposed to unfamiliar persons or to possible scrutiny by others. The lifetime prevalence of SP is estimated to be as high as 13%. It is frequently co-morbid with and usually precedes the onset of other psychiatric illnesses and is associated with significant occupational and social impairment, including academic and vocational underachievement. Fortunately, there are effective treatments for this common and debilitating condition. There is currently considerable evidence for the efficacy of pharmacotherapy and especially the monoamine oxidase inhibitors (MAOIs) and selective serotonin re-uptake inhibitors (SSRIs) in the treatment of this disorder. However, SSRIs are generally preferred as the first-line treatment of choice due to the advantages of SSRIs over MAOIs in terms of safety and tolerability. Despite encouraging results, current treatments most often produce partial symptomatic improvement, rather than high end-state functioning. While current first line treatments for social phobia target the serotonergic system, it is important to remember that different social fears are likely to have different developmental roots and may be based on quite different neurobiological systems. In this article we provide a review of current pharmacotherapeutic options for SP, current knowledge of the neurobiology of SP, and a review of new and promising directions in pharmacological research. It is increasingly clear that serotonin (5-HT) is unlikely to be the whole story in SP and that other brain chemical systems, especially the dopaminergic, noradrenaline-corticotropin releasing hormone and gamma-aminobutyric acid (GABA) dependent systems, most probably have an important role to play in a substantial percentage of cases. A number of new and novel agents, including the substance P antagonists, GABA agonists and CRF antagonists show considerable promise in the treatment of SP. However, in order to enhance the understanding of the neurobiology and treatment response of SP, we need to develop more sophisticated theory-driven typologies of SP.

The neurobiology of social phobia: from pharmacotherapy to brain imaging

Social phobia is a common psychiatric disorder that is often associated with significant psychiatric comorbidity and disability. There is currently considerable evidence for the efficacy of pharmacotherapy, especially the selective serotonin reuptake inhibitors, in the treatment of this disorder. In addition, researchers have recently begun to explore the underlying neurobiology of social phobia with results that will likely have important implications for future treatments. This article provides a review of the results to date of controlled medication trials. A review of chemical and neuroendocrine challenges, neurotransmitter functioning, and neuroimaging studies in social phobia is provided, followed by a discussion of the implications of these findings for future treatment and research.

Functional brain imaging and pharmacotherapy in social phobia: single photon emission computed tomography before and after treatment with the selective serotonin reuptake inhibitor citalopram

1. Despite increased understanding of the prevalence and pharmacotherapy of social phobia (or social anxiety disorder), the neurobiology of the disorder is little understood. 2. Little data exists on the effect of pharmacotherapeutic intervention on regional cerebral blood flow (rCBF) in this disorder. Patients (n=15) who met DSM-IV diagnostic criteria for social phobia were subjected to single photon emission computed tomography (SPECT) with technetium-99m hexamethylpropylene amine oxime (Tc-99m HMPAO) before and after an eight-week trial of pharmacotherapy with the selective serotonin reuptake inhibitor (SSRI) citalopram. 3. Pharmacotherapy led to significantly reduced activity in the anterior and lateral part of the left temporal cortex; the anterior, lateral and posterior part of the left mid frontal cortex; and the left cingulum. 4. Despite the small sample size, medication non-responders (n=6) had higher activity at baseline in the anterior and lateral part of the left temporal cortex and the lateral part of the left mid frontal regions compared with responders (n=9). These data from this exploratory study are consistent with work suggesting that the anxiety disorders share certain mediating neurocircuitry, although activity in other brain regions may differ. 5. Further research is necessary to determine the neurobiological underpinnings of social phobia.

Neurobiology of social phobia

Social phobia is an anxiety disorder that is characterized by excessive fear and/or avoidance of situations in which an individual believes that he or she may be the subject of evaluation or scrutiny while interacting with other people or performing a specific task. This article reviews the available literature on the neurobiology underlying social phobia, including autonomic nervous system effects, neuroimaging findings, pharmacologic challenge studies, and neuroendocrine responsivity and function. Overall, such studies have found few consistently demonstrable differences in neurobiology between patients with social phobia and healthy controls, but further investigations are needed.

Subcortical correlates of differential classical conditioning of aversive emotional reactions in social phobia

BACKGROUND

Conditioning processes have been proposed to play a role in the development of anxiety disorders. As yet, the neurobiologic correlates of emotional learning have not been fully understood in these patients. Accordingly, brain activity was studied in subcortical and cortical regions involved in the processing of negative affect during differential aversive classical conditioning.

METHODS

Twelve patients with social phobia and 12 healthy control subjects were presented with paired conditioned (CS; neutral facial expressions) and unconditioned stimuli (US; negative odor vs unmanipulated air). Functional magnetic resonance imaging (fMRI) was utilized to examine regional cerebral activity during habituation, acquisition,a nd extinction trials. Activity was measured with echo-planar-imaging (EPI), and signal intensity in individually defined anatomic regions were analyzed.

RESULTS

Subjective ratings of emotional valence to the CS indicated that behavioral conditioning occurred in both groups. The presentation of CS associated with negative odor led to signal decreases in the amygdala and hippocampus of normal subjects, whereas an opposite increased activation in both regions was observed in patients. Regional differences were not found during habituation and extinction.

CONCLUSIONS

Results suggest that conditioned aversive stimuli are processed in subcortical regions, with phobic patients differing from control subjects.

Neurobiological perspectives on social phobia: from affiliation to zoology

Social phobia (or "social anxiety disorder") is a prevalent condition that has been the subject of increased scrutiny in recent years. The purpose of this paper is to review the neurobiology of social phobia. It is apparent from the extant literature that this disorder is poorly understood from a neurobiological perspective. There are nonetheless a number of clinical and preclinical observations which, at times, converge to illuminate areas worthy of further study. Included in this category are suggestive findings of central serotonergic dysregulation in social phobia, response to serotonin reuptake inhibitors in social phobia, and the role of serotonergic function in septohippocampal models of anxiety. Abnormalities in central dopaminergic function are also posited, supported to some extent by recent neuroimaging findings. There are in addition a number of animal and human behavioral models in existence that may be relevant to the study of social phobia. Included in this category are models of social dominance in wild baboons, social affiliation in the prairie vole, and behavioral inhibition to the unfamiliar in childhood. Newer technologies that are likely to play a major role in the delineation of the neural circuitry (e.g., functional magnetic resonance imaging) and heritability (e.g., molecular genetics) of social phobia are discussed. Finally, an interactive role for biology and experience in the expression of social phobia is considered.