Temporal lobe abnormalities in panic disorder: an MRI study

Environmental Enrichment Facilitates Anxiety in Conflict-Based Tests but Inhibits Predator Threat-Induced Defensive Behaviour in Male Mice

INTRODUCTION

Environmental enrichment (EE) is a useful and sophisticated tool that improves rodents' well-being by stimulating social behaviour and cognitive, motor, and sensory functions. Exposure to EE induces neuroplasticity in different brain areas, including the limbic system, which has been implicated in the control of anxiety and fear. However, the effects of EE on ethologically relevant naturalistic behaviours, such as those displayed by prey in the presence of predators, remain largely unexplored.

MATERIAL AND METHODS

In the present study, we investigated anxiety- and panic attack-like behaviours in a predator (cat)-prey confrontation paradigm and compared them with those in classical assays, such as the elevated plus-maze (EPM), marble-burying, and open field tests (OFTs), using C57BL/6J male mice housed in enriched or standard environments for 6 weeks.

RESULTS

We observed that EE exposure caused enhancement of the levels of anxiety-like behaviours in the EPM and OFTs, increasing risk assessment (an anxiety-related response), and decreasing escape (a panic attack-like response) behaviours during exposure to the predator versus prey confrontation paradigm.

CONCLUSION

Taken together, our findings suggest that enriched external environments can modify the processing of fear- and anxiety-related stimuli in dangerous situations, changing the decision-making defensive strategy.

Association between cortical thickness and anxiety measures: A scoping review

Cortical thickness has been increasingly studied in the context of structural-brain-behavior associations, such as anxiety; however, the literature is scattered across methods and research fields. This scoping review aims to summarize the available data concerning the association between cortical thickness and anxiety-related measures and identify the current research gaps. Searches were conducted in PubMed, PsycINFO/PsycARTICLES, Web of Science, OpenGrey and Networked Digital Library of Theses and Dissertations, and reference lists of key studies. Two researchers independently screened the abstracts and full-text reports according to the eligibility criteria, as well as extracted and charted the data. Quantitative and descriptive syntheses were conducted. The included publications (n = 18) reported cross-sectional studies, and 17 used surface-based approaches to estimate cortical thickness. Differences in regional cortical thickness were found to be associated with different anxiety-related measures/processes. Brain regions of interest include the medial orbitofrontal cortex, the ventromedial prefrontal cortex, the insula, the temporo-parietal areas, and the anterior cingulate cortex. However, caution should be warranted when interpreting the available results, as there is high variability in the field across anxiety-related measures, distinctive anxiety disorders, and data processing conditions and analysis. More research into this association is needed, to replicate and clarify existing findings.

Distinct grey matter volume alterations in adult patients with panic disorder and social anxiety disorder: A systematic review and voxel-based morphometry meta-analysis

BACKGROUND

The paradox of similar diagnostic criteria but potentially different neuropathologies in panic disorder (PD) and social anxiety disorder (SAD) needs to be clarified.

METHODS

We performed a qualitative systematic review and a quantitative whole-brain voxel-based morphometry (VBM) meta-analysis with an anisotropic effect-size version of seed-based D mapping (AES-SDM) to explore whether the alterations of grey matter volume (GMV) in PD are similar to or different from those in SAD, together with potential confounding factors.

RESULTS

A total of thirty-one studies were eligible for inclusion, eighteen of which were included in the meta-analysis. Compared to the respective healthy controls (HC), qualitative and quantitative analyses revealed smaller cortical-subcortical GMVs in PD patients in brain areas including the prefrontal and temporal-parietal cortices, striatum, thalamus and brainstem, predominantly right-lateralized regions, and larger GMVs in the prefrontal and temporal-parietal-occipital cortices, and smaller striatum and thalamus in SAD patients. Quantitatively, the right inferior frontal gyrus (IFG) deficit was specifically implicated in PD patients, whereas left striatum-thalamus deficits were specific to SAD patients, without shared GMV alterations in both disorders. Sex, the severity of clinical symptoms, psychiatric comorbidity, and concomitant medication use were negatively correlated with smaller regional GMV alterations in PD patients.

CONCLUSION

PD and SAD may represent different anxiety sub-entities at the neuroanatomical phenotypes level, with different specific neurostructural deficits in the right IFG of PD patients, and the left striatum and thalamus of SAD patients. This combination of differences and specificities can potentially be used to guide the development of diagnostic biomarkers for these disorders.

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.

Reduced Cortical Thickness in the Temporal Pole, Insula, and Pars Triangularis in Patients with Panic Disorder

PURPOSE

Recent neuroimaging findings have revealed that paralimbic and prefrontal regions are involved in panic disorder (PD). However, no imaging studies have compared differences in cortical thickness between patients with PD and healthy control (HC) subjects.

MATERIALS AND METHODS

Forty-seven right-handed patients with PD who met the diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders-4th edition-text revision, and 30 HC subjects were enrolled. We used the FreeSurfer software package for estimating the cortical thickness of regions of interest, including the temporal pole, insula, and pars triangularis (mid-ventrolateral prefrontal cortex).

RESULTS

Cortical thickness of the temporal pole (p=0.033, right), insula (p=0.017, left), and pars triangularis (p=0.008, left; p=0.025, right) in patients with PD was significantly lower, compared with HC subjects (Benjamini-Hochberg false discovery rate correction). Exploratory analysis revealed a significant negative correlation between the cortical thickness of the right temporal pole and Beck Depression Inventory scores (r=-0.333, p=0.027) in patients with PD and positive correlations between the cortical thickness of the left pars triangularis and Panic Disorder Severity Scale (r=0.429, p=0.004), Anxiety Sensitivity Index-Revised (r=0.380, p=0.011), and Beck Anxiety Inventory (r=0.421, p=0.004) scores using Pearson's correlation.

CONCLUSION

Ours study is the first to demonstrate cortical thickness reduction in the temporal pole, insula, and pars triangularis in patients with PD, compared with the HC subjects. These findings suggest that reduced cortical thickness could play an important role in the pathophysiology of PD.

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.

Differential alterations of resting-state functional connectivity in generalized anxiety disorder and panic disorder

Generalized anxiety disorder (GAD) and panic disorder (PD) are most common anxiety disorders with high lifetime prevalence while the pathophysiology and disease-specific alterations still remain largely unclear. Few studies have taken a whole-brain perspective in the functional connectivity (FC) analysis of these two disorders in resting state. It limits the ability to identify regionally and psychopathologically specific network abnormalities with their subsequent use as diagnostic marker and novel treatment strategy. The whole brain FC using a novel FC metric was compared, that is, scaled correlation, which they demonstrated to be a reliable FC statistics, but have higher statistical power in two-sample t-test of whole brain FC analysis. About 21 GAD and 18 PD patients were compared with 22 matched control subjects during resting-state, respectively. It was found that GAD patients demonstrated increased FC between hippocampus/parahippocampus and fusiform gyrus among the most significantly changed FC, while PD was mainly associated with greater FC between somatosensory cortex and thalamus. Besides such regional specificity, it was observed that psychopathological specificity in that the disrupted FC pattern in PD and GAD correlated with their respective symptom severity. The findings suggested that the increased FC between hippocampus/parahippocampus and fusiform gyrus in GAD were mainly associated with a fear generalization related neural circuit, while the greater FC between somatosensory cortex and thalamus in PD were more likely linked to interoceptive processing. Due to the observed regional and psychopathological specificity, their findings bear important clinical implications for the potential treatment strategy.

Panic and agoraphobia associated with a cerebral arteriovenous malformation

A patient with epilepsy developed panic and agoraphobia. A large right temporo-parietal, arteriovenous malformation was detected. The relationship between these disorders is discussed.

Advances in the neuroimaging of panic disorder

Models of the neuroanatomy of panic disorder (PD) have relied on both animal work on fear and on clinical data from neuroimaging. Early work hypothesised a network of brain regions involved in fear processing (e.g. the amygdala), but more recent work has also pointed to the involvement of other cortical areas and other brain circuitry (e.g. the insula and anterior cingulate cortex). Studies investigating functional and structural brain connectivity in PD may ultimately shed light on the extent to which the neuroanatomy of PD is localised versus distributed, and on how current treatments alter this neuroanatomy.

Orbito-frontal cortex volumes in panic disorder

OBJECTIVE

Given the association between the pathophysiology of panic disorder and prefrontal cortex function, we aimed to perform a volumetric MRI study in patients with panic disorder and healthy controls focusing on the in vivo neuroanatomy of the OFC.

METHODS

Twenty right-handed patients with panic disorder and 20 right-handed healthy control subjects were studied. The volumes of whole brain, total white and gray matters, and OFC were measured by using T1-weighted coronal MRI images, with 1.5-mm-thick slices, at 1.5T. In addition, for psychological valuation, Hamilton Depression Rating (HDRS) and Panic Agoraphobia Scales (PAS) were administered.

RESULTS

Unadjusted mean volumes of the whole brain volume, total white and gray matter were not different between the patients and healthy controls while the patient group had significantly smaller left (t=-6.70, p<0.0001) and right (t=-5.86, p<0.0001) OFC volumes compared with healthy controls.

CONCLUSION

Our findings indicate an alteration of OFC morphology in the panic disorder and suggest that OFC abnormalities may be involved in the pathophysiology of panic disorder.

The role of the amygdala in the pathophysiology of panic disorder: evidence from neuroimaging studies

Although the neurobiological mechanisms underlying panic disorder (PD) are not yet clearly understood, increasing amount of evidence from animal and human studies suggests that the amygdala, which plays a pivotal role in neural network of fear and anxiety, has an important role in the pathogenesis of PD. This article aims to (1) review the findings of structural, chemical, and functional neuroimaging studies on PD, (2) relate the amygdala to panic attacks and PD development, (3) discuss the possible causes of amygdalar abnormalities in PD, (4) and suggest directions for future research.

Revise the revised? New dimensions of the neuroanatomical hypothesis of panic disorder

In 2000, Gorman et al. published a widely acknowledged revised version of their 1989 neuroanatomical hypothesis of panic disorder (PD). Herein, a 'fear network' was suggested to mediate fear- and anxiety-related responses: panic attacks result from a dysfunctional coordination of 'upstream' (cortical) and 'downstream' (brainstem) sensory information leading to heightened amygdala activity with subsequent behavioral, autonomic and neuroendocrine activation. Given the emergence of novel imaging methods such as fMRI and the publication of numerous neuroimaging studies regarding PD since 2000, a comprehensive literature search was performed regarding structural (CT, MRI), metabolic (PET, SPECT, MRS) and functional (fMRI, NIRS, EEG) studies on PD, which will be reviewed and critically discussed in relation to the neuroanatomical hypothesis of PD. Recent findings support structural and functional alterations in limbic and cortical structures in PD. Novel insights regarding structural volume increase or reduction, hyper- or hypoactivity, laterality and task-specificity of neural activation patterns emerged. The assumption of a generally hyperactive amygdala in PD seems to apply more to state than trait characteristics of PD, and involvement of further areas in the fear circuit, such as anterior cingulate and insula, is suggested. Furthermore, genetic risk variants have been proposed to partly drive fear network activity. Thus, the present state of knowledge generally supports limbic and cortical prefrontal involvement as originally proposed in the neuroanatomical hypothesis. Some modifications might be suggested regarding a potential extension of the fear circuit, genetic factors shaping neural network activity and neuroanatomically informed clinical subtypes of PD potentially guiding future treatment decisions.

Hippocampal neurochemical pathology in patients with panic disorder

OBJECTIVE

In the present study, we measured hippocampal N-acetyl-l-aspartate (NAA), choline (CHO) and creatine (CRE) values in patients with panic disorder and healthy control subjects using in vivo(1)H MRS.

METHODS

We scanned 20 patients meeting Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) criteria for panic disorder and 20 matched healthy controls with a 1.5 Tesla GE Signa Imaging System and measured of NAA, CHO, and CRE in hippocampal regions.

RESULTS

When NAA, CHO and CRE values were compared between groups, statistically significant lower levels for all ones were detected for both sides.

CONCLUSION

Consequently, in the present study we found that NAA, CHO and CRE values of the patients with panic disorder were lower than those healthy controls. Future studies involving a large number of panic patients may shed further light on the generalizability of the current findings to persons with panic disorder.

The diagnostic value of clinical EEG in detecting abnormal synchronicity in panic disorder

Electroencephalographic (EEG) findings repeatedly reported abnormal synchronous or even epileptiform discharges in panic disorder. Although less frequently occurring in patients with panic disorder, these deviant EEG features during panic attacks were also observed in intracranial EEG. For this purpose, our article reviews the consideration of abnormal synchronous neuronal activity in different neurocircuits, particularly limbic, as a suggested condition of panic attacks. Therapeutic approaches of anticonvulsants have shown reductions of symptoms and frequency of attacks in numerous patients suffering from panic disorder, supporting the presumption of underlying abnormal synchronous neuronal activity. Thus, scalp EEG recordings are still recommended for discovering indications of abnormal synchronous neuronal activity in panic patients.

A review of neuroimaging studies of anxiety disorders in China

BACKGROUND

Anxiety disorders are highly prevalent internationally, and constitute a substantial social and economic burden for patients, their families, and society. A number of neuroimaging studies have investigated the etiology of anxiety disorders in China in the last decade. We discuss the findings of these studies, and compare them with the results of neuroimaging studies of anxiety disorders outside China.

METHOD

A literature search was conducted using the Chinese BioMedical Literature Database, the Chinese Scientific and Technical Periodicals Database, the Chinese Journal Full-text Database, and PubMed, from 1989 to April 2009. We selected neuroimaging studies in which all participants and researchers were Chinese.

RESULTS

Twenty-five studies fit our inclusion criteria. Nine studies examined general anxiety disorder (GAD) and/or panic disorder (PD), eight examined obsessive-compulsive disorder (OCD), and eight examined posttraumatic stress disorder (PTSD). Our literature review revealed several general findings. First, reduced regional cerebral blood flow (rCBF) was found in the frontal lobe and temporal lobe in patients with GAD and PD compared with healthy controls. Second, when viewing images with negative and positive valence, relatively increased or decreased activation was found in several brain areas in patients with GAD and PD, respectively. Third, studies with positron emission tomography (PET) and magnetic resonance spectroscopy (MRS) imaging revealed that OCD patients exhibited hyperperfusion and hypoperfusion in some brain regions compared with healthy controls. Neuroimaging studies of PTSD indicate that the hippocampal volume and the N-acetylaspartic acid (NAA) level and the NAA/creatine ratio in the hippocampus are decreased in patients relative to controls.

CONCLUSION

Neuroimaging studies within and outside China have provided evidence of specific neurobiological changes associated with anxiety disorders. However, results have not been entirely consistent across different studies of patients with the same diagnoses. International collaborative research using large samples and robust designs should be conducted in future.

Temporal and right frontal lobe alterations in panic disorder: a quantitative volumetric and voxel-based morphometric MRI study

BACKGROUND

With regard to current neurobiological theories, the aim of our study was to examine possible alterations of temporal and frontal lobe volume in panic disorder (PD).

METHOD

Seventeen in-patients with PD and a group of healthy control subjects (HC) matched for age and gender were investigated by quantitative volumetric magnetic resonance imaging (MRI). Structures of interest were: the temporal lobe, the amygdala-hippocampus complex (AHC) and the frontal lobe. In addition, a voxel-based morphometry (VBM) analysis implemented in Statistical Parametric Mapping 5 (SPM5) was used for a more detailed assessment of possible volume alterations. Modulated grey matter (GM) images were used to test our a priori hypotheses and to present the volumetric results.

RESULTS

Quantitative volumetric MRI revealed a bilateral reduction in temporal lobe volume in patients with PD compared to HC subjects. The AHC was normal. The right frontal lobe volume was also decreased. Using VBM we detected a significant GM volume reduction in the right middle temporal gyrus [Brodmann area (BA) 21] in patients with PD. In addition, there was a reduction in GM volume in the medial part of the orbitofrontal cortex (BA 11).

CONCLUSIONS

Our results of reduced temporal and frontal lobe volume in PD are in agreement with prior studies. By using a recent VBM approach we were able to assess the abnormalities more precisely. The location of GM volume reduction in the right middle temporal gyrus and medial orbitofrontal cortex lends further support to recent aetiological models of PD.

Increased prevalence of white matter hyperintensities in patients with panic disorder

The aim of the current study is to compare the prevalence, severity and location of cerebral white matter hyperintensities (WMH) between patients with panic disorder (PD) and healthy control subjects. Patients with PD (n = 24) and matched healthy control subjects (n = 24) were scanned using a 3.0 Tesla whole-body magnetic resonance scanner. Axial T2-weighted and fluid-attenuated inversion recovery images were acquired and evaluated for the prevalence, severity and location of WMH using the modified composite scale of Fazekas and Coffey and coded separately for deep and periventricular WMH. Logistic regression analyses were used to assess the association between WMH and the diagnosis of PD. A greater severity of total WMH was associated with a diagnosis of PD in a dose-dependent pattern (odds ratio [OR] = 8.8, P = 0.005 for mild WMH; OR = 27.7, P = 0.007 for moderate to severe WMH). Deep WMH, where most group differences originated, were predominantly located in the frontal region of the brain (n = 16 in PD, n = 1 in control). The current report is the first study to report an increased prevalence of WMH in patients with PD.

Sexually dimorphic gray matter volume reduction in patients with panic disorder

While clinical features of panic disorder show significant sexual dimorphism, previous structural MRI studies have not sufficiently controlled for sex when looking at regional brain abnormalities in panic disorder. Using optimized voxel-based morphometry (VBM), regional gray matter volume was compared between 24 patients (male/female: 9/15) with panic disorder and 24 healthy subjects matched for age and sex. Significant gray matter volume reductions were found in the bilateral dorsomedial and right ventromedial prefrontal cortices, right amygdala, anterior cingulate cortex, bilateral insular cortex, occipitotemporal gyrus and left cerebellar vermis in the patients compared with the controls. Among these regions, the VBM revealed significant sexual dimorphism: volume reduction in the right amygdala and the bilateral insular cortex was significantly greater in the males, while reduction in the right superior temporal gyrus was greater in females. Furthermore, a significant reduction in the dorsolateral and ventrolateral prefrontal cortices, thalamus, and parietal cortex was specific to the female patients. The present study demonstrated the morphological changes in extensive brain regions of patients with panic disorder compared with the sex-matched controls. The current results further suggested that the sexually dimorphic clinical phenotypes of panic disorder might have a neurobiological background even at the structural level of the brain.

Smaller amygdala is associated with anxiety in patients with panic disorder

AIMS

Anxiety a core feature of panic disorder, is linked to function of the amygdala. Volume alterations in the brain of patients with panic disorder have previously been reported, but there has been no report of amygdala volume association with anxiety.

METHODS

Volumes of hippocampus and amygdala were manually measured using magnetic resonance imaging obtained from 27 patients with panic disorder and 30 healthy comparison subjects. In addition the amygdala was focused on, applying small volume correction to optimized voxel-based morphometry (VBM). State-Trait Anxiety Inventory and the NEO Personality Inventory Revised were also used to evaluate anxiety.

RESULTS

Amygdala volumes in both hemispheres were significantly smaller in patients with panic disorder compared with control subjects (left: t = -2.248, d.f. = 55, P = 0.029; right: t = -2.892, d.f. = 55, P = 0.005). VBM showed that structural alteration in the panic disorder group occurred on the corticomedial nuclear group within the right amygdala (coordinates [x,y,z (mm)]: [26,-6,-16], Z score = 3.92, family-wise error-corrected P = 0.002). The state anxiety was negatively correlated with the left amygdala volume in patients with panic disorder (r = -0.545, P = 0.016).

CONCLUSIONS

These findings suggested that the smaller volume of the amygdala may be associated with anxiety in panic disorder. Of note, the smaller subregion in the amygdala estimated on VBM could correspond to the corticomedial nuclear group including the central nucleus, which may play a crucial role in panic attack.

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.

Panic disorder: is the PAG involved?

Data from studies with humans have suggested that abnormalities of midbrain structures, including the periaqueductal gray matter (PAG), could be involved in the neurobiology of panic disorder (PD). The electrical stimulation of the PAG in neurosurgical patients induces panic-like symptoms and the effect of drugs that are effective in the treatment of PD in the simulation of public speaking model of anxiety is in agreement with data from animal models of PD. Structural neuroimaging studies have shown increases in gray matter volume of midbrain and pons of PD patients. There is also evidence of lower serotonin transporter and receptor binding, and increases of metabolism in the midbrain of PD patients. Nevertheless, these midbrain abnormalities can not be considered as specific findings, since neuroimaging data indicate that PD patients have abnormalities in other brain structures that process fear and anxiety.

Structural magnetic ressonance imaging in anxiety disorders: an update of research findings

OBJECTIVE: The aim of the present report is to present a systematic and critical review of the more recent literature data about structural abnormalities detected by magnetic ressonance in anxiety disorders. METHOD: A review of the literature in the last five years was conducted by a search of the Medline, Lilacs and SciELO indexing services using the following key words: "anxiety", "panic", "agoraphobia", "social anxiety", "posttraumatic" and "obsessive-compulsive", crossed one by one with "magnetic resonance", "voxel-based", "ROI" and "morphometry". RESULTS: We selected 134 articles and 41 of them were included in our review. Recent studies have shown significant morphological abnormalities in various brain regions of patients with anxiety disorders and healthy controls. Despite some apparently contradictory findings, perhaps reflecting the variability and limitations of the methodologies used, certain brain regions appear to be altered in a consistent and relatively specific manner in some anxiety disorders. These include the hippocampus and the anterior cingulate cortex in posttraumatic stress disorder and the orbitofrontal cortex in obsessive-compulsive disorder. CONCLUSIONS: The present review indicates that structural neuroimaging has contributed to a better understanding of the neurobiology of anxiety disorders. Further development of neuroimaging techniques, better sample standardization and the integration of data across neuroimaging modalities may extend progress in this area.

Regional gray matter abnormalities in panic disorder: a voxel-based morphometry study

Although abnormalities in brain structures involved in the neurobiology of fear and anxiety have been implicated in the pathophysiology of panic disorder (PD), relatively few studies have made use of voxel-based morphometry (VBM) magnetic resonance imaging (MRI) to determine structural brain abnormalities in PD. We have assessed gray matter volume in 19 PD patients and 20 healthy volunteers using VBM. Images were acquired using a 1.5 T MRI scanner, and were spatially normalized and segmented using optimized VBM. Statistical comparisons were performed using the general linear model. A relative increase in gray matter volume was found in the left insula of PD patients compared with controls. Additional structures showing differential increases were the left superior temporal gyrus, the midbrain, and the pons. A relative gray matter deficit was found in the right anterior cingulate cortex. The insula and anterior cingulate abnormalities may be relevant to the pathophysiology of PD, since these structures participate in the evaluation process that ascribes negative emotional meaning to potentially distressing cognitive and interoceptive sensory information. The abnormal brain stem structures may be involved in the generation of panic attacks.

Altered cingulate white matter connectivity in panic disorder patients

OBJECTIVE

Functional imaging studies of panic disorder subjects suggest an increased activation of the cingulate regions of the brain. Aim of the current study was to explore the white matter connectivity differences between subjects with panic disorder and healthy comparison subjects.

METHOD

Structural white matter connectivity, as determined from fractional anisotropy (FA) values obtained by diffusion tensor imaging, was assessed for anterior and posterior cingulate regions in 24 panic disorder patients and 24 age and sex-matched healthy comparison subjects.

RESULTS

Subjects with panic disorder exhibited significantly greater FA values in left anterior and right posterior cingulate regions (by 13.3% and 19.6%, respectively) relative to comparison subjects. White matter connectivity for these two cingulate regions was also positively correlated with clinical severity, as determined by Panic Disorder Severity Scale. FA values in left anterior cingulate region negatively correlated with the time of Trail Making Tests and positively with Digit Symbol Substitution Test.

CONCLUSIONS

Findings suggest a potential 'enhancement' in white matter connectivity in left anterior and right posterior cingulate regions in panic disorder, and that these changes may play an important role in mediating clinical symptoms of panic disorder.

Panic disorder: the psychobiology of external treat and introceptive distress

Panic disorder seems to be mediated by the neuronal circuitry and neurochemical systems that have evolved to respond to external threatening stimuli. Distant threats activate prefrontal cortex (involved in complex planning of avoidance strategies), while immediate threats activate midbrain structures (involved in fast reflexive behaviors). Panic disorder may, however, also involve more specific interoceptive mechanisms. For example, the association between respiratory dysfunction and panic disorder has bolstered a false suffocation alarm hypothesis. Genetic and environmental contributors to panic disorder are beginning to be delineated. Effective pharmacotherapy and psychotherapy are able to normalize the relevant psychobiology.

Decreased GABA levels in anterior cingulate and basal ganglia in medicated subjects with panic disorder: a proton magnetic resonance spectroscopy (1H-MRS) study

The purpose of this study was to investigate the brain gamma-aminobutyric acid (GABA) concentration and its relationship with clinical variables in patients with panic disorder (PD). Single voxel proton magnetic resonance spectroscopy ((1)H-MRS) scan was performed on 22 medicated subjects with PD and 25 age and sex-matched healthy comparison subjects. GABA and other metabolite levels were measured in the anterior cingulate cortex (ACC) and basal ganglia. GABA levels were significantly lower in the ACC and basal ganglia of PD patients relative to comparison subjects. Lactate and choline concentrations in the ACC in PD patients were also higher than in the comparison subjects. Our data suggested in part that alterations of the GABA function and the energy metabolism in ACC and basal ganglia may play an important role in the pathophysiology of panic disorder.

Decreased blood flow of temporal regions of the brain in subjects with panic disorder

OBJECT

The purpose of the current study was to investigate alterations of regional cerebral blood flow (rCBF) in subjects with panic disorder.

METHODS

Twenty-two subjects with panic disorder who were under psychotropic medications and 25 age and gender-matched healthy comparison subjects were assessed regarding the rCBF of using Tc-99m-hexamethyl propylenamino oxime single photon emission tomography (SPECT). Using statistical parametric mapping, the rCBF was compared between panic disorder and healthy comparison groups.

RESULTS

Decreased rCBF flow in right superior temporal lobe was observed in subjects with panic disorder (p<0.05 after correction for multiple comparisons). The rCBF in right superior temporal gyrus negatively correlated with the duration of illness, scores of panic disorder severity scale (PDSS), Hamilton anxiety rating scale (HARS) and Zung self-rating anxiety scale (Z-SAS).

CONCLUSION

We report that there is a decreased cerebral blood flow of temporal regions of the brain in panic disorder and that this decrease may, in part, reflect the clinical severity of panic disorder.

Increased brainstem volume in panic disorder: a voxel-based morphometric study

Neurocircuitry models of panic disorder have hypothesized that the panic attack itself stems from loci in the brainstem including the ascending reticular system and respiratory and cardiovascular control centers. Voxel-based morphometry with acobian modulation was used to examine gray matter volume changes in 10 panic disorder patients and 23 healthy controls. The panic disorder patients had a relatively increased gray matter volume in the midbrain and rostral pons of the brainstem. Increased ventral hippocampal and decreased regional prefrontal cortex volumes were also noted at a lower significance threshold. This finding has implications for pathophysiologic models of panic disorder, and provides structural evidence for the role of the brainstem in neurocircuitry models of panic disorder.

Putaminal gray matter volume decrease in panic disorder: an optimized voxel-based morphometry study

Our study aimed to identify gray matter volume differences between panic disorder patients and healthy volunteers using optimized voxel-based morphometry. Gray matter volume was compared between 18 panic subjects and 18 healthy volunteers. Panic disorder severity scale (PDSS) and Zung self-rating anxiety scale (Z-SAS) were administered. Gray matter volumes of bilateral putamen were decreased in panic subjects relative to healthy comparison subjects (corrected P < 0.05). Decreased gray matter volume was also observed in the right precuneus, right inferior temporal gyrus, right inferior frontal gyrus, left superior temporal gyrus, and left superior frontal gyrus at a less conservative level of significance. PDSS score negatively correlated with gray matter volume in the left putamen, right putamen, right inferior frontal gyrus, and left superior frontal gyrus in panic subjects. The duration of illness negatively correlated with left putaminal gray matter volume. There was also a negative correlation between gray matter volume in right putamen and Z-SAS score in panic subjects. The current study reports a putaminal gray matter volume decrease in panic subjects, which may be related to the clinical severity of panic disorder.

Association of human hippocampal neurochemistry, serotonin transporter genetic variation, and anxiety

The impact of the serotonin transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) on anxiety-related behavior and related cerebral activation has facilitated the understanding of neurobiological mechanisms of anxiety. However, the influence of the 5-HTTLPR genotype on hippocampal neuronal development and neurochemistry, which is relevant to anxiety behavior, has not been investigated. In 38 healthy subjects, absolute concentrations of N-acetylaspartate (NAA) were measured as a main surrogate parameter for hippocampal neurochemistry on a 3-T scanner. A significantly lower hippocampal NAA concentration in s allele carriers was observed as compared to l/l genotype. Other metabolites (choline, creatine + phosphocreatine, glutamate) were unaffected by genotype. The hippocampal NAA concentration was negatively correlated with trait anxiety scores (STAI). Metabolites measured in the anterior cingulate cortex (reference region) were not associated with genotype. The results are in accordance with the recently reported relationship between hippocampal neuronal development and anxiety behavior in adult animals and show an association between human limbic neurochemistry and genetically driven serotonergic neurotransmission relevant to anxiety.

[The contribution of brain imaging to the study of panic disorder]

AIMS

The present review is aimed to evaluate the recent contribution of brain imaging techniques to the definition of neuroanatomofunctional models of panic disorder (PD).

METHODS

Structural and functional brain imaging studies of PD, conducted from January 1993 to October 2003 and selected through a comprehensive Medline search (key-words: panic disorder, emotions, brain imaging, EEG, Event-Related Potentials, MRI, fMRI, PET, SPECT, TC) were included in the review. The Medline search has been complemented by bibliographic cross-referencing.

RESULTS

The majority of the reviewed studies suggests that a dysfunction of a neural circuit encompassing prefrontal and temporo-limbic cortices is present in PD. A right hemisphere preferential involvement in PD has been shown by several studies.

CONCLUSIONS

Reviewed neuroimaging studies suggest a dysfunction of frontal and temporo-limbic circuitries in PD. However, those studies cannot be considered conclusive because of several methodological limitations. Longitudinal and multi-modal studies involving larger patient samples, possibly integrated with population-based and genetic studies, would provide more insight into pathophysiological mechanisms of PD.

DECLARATION OF INTEREST

Authors declare that none of them had any known real, potential, or apparent conflict of interest and that there was no business or personal interest that might be relevant to the topic of this article.

EEG coherence analysis in never-medicated patients with panic disorder

To investigate the functional abnormalities in the central nervous system (CNS) of patients with panic disorder (PD), we compared the electroencephalography (EEG) coherence values in 18 never-medicated PD patients with those in age-matched normal control subjects, and examined the relationships between EEG coherence values and both the duration of disease and the severity of panic attacks. EEG data were recorded in the resting state. The PD patients had lower coherence values with significant differences in F3-F4, C3-C4, P3-P4, F7-T5, and F8-T6. There were positive correlations for the higher alpha band between coherence values and both the duration of disease and the severity of panic attacks. These findings provide further evidence that PD patients have a lower degree of inter-hemispheric functional connectivity in the frontal region and intra-hemispheric functional connectivity in the bilateral temporal region, and that chronic condition or frequent panic attacks in PD patients may be related to the pathophysiological CNS changes.

Reduced brain serotonin transporter binding in patients with panic disorder

There is strong evidence for the importance of the serotonin (5-HT) system in the neurobiology of panic disorder (PD); however, the exact role of this system remains unclear. The 5-HT transporter (5-HTT) is a key element in 5-HT neurotransmission. The current study aimed to investigate the binding of 5-HTT in the brain of patients with PD. We used single-photon emission computed tomography with a radioligand that specifically labels the 5-HTT, [(123)I]nor-beta-CIT. Subjects comprised eight patients with current PD, eight patients with PD in remission, and eight healthy control subjects. The patients with current PD showed a significant decrease in 5-HTT binding in the midbrain, in the temporal lobes and in the thalamus in comparison to the controls. The binding of 5-HTT in patients with PD in remission was similar to findings in the control group in the midbrain and in the temporal lobes, but lower in the thalamus. Regional 5-HTT binding significantly and negatively correlated with the severity of panic symptoms. These findings point to a dysregulation of the 5-HT system in PD patients. Altered function of 5-HTT appears to be related to the clinical status of patients. Clinical improvement in the patients in remission is associated with normalization of 5-HTT binding.

White matter hyperintensities in subjects with bipolar disorder

There have been divergent reports on the prevalence and severity of white matter hyperintensities (WMH) on brain magnetic resonance (MR) images in subjects with bipolar disorder. In the present study, evaluations were made on the prevalence and severity of WMH in subjects with bipolar disorder using contiguous 3-mm thick MR slices as well as fluid attenuated inversion recovery (FLAIR) images. A detailed WMH rating system was employed to assess these WMH. A total of 43 bipolar patients, as diagnosed by the Structured Clinical Interview from the Diagnostic and Statistical Manual-IV (SCID-IV), and 39 healthy comparison subjects were scanned using a 1.5-T whole body GE magnetic resonance scanner. WMH were assessed with a modified composite version of the Fazekas' and Coffey's rating scales to detect less severe WMH. Periventricular and subcortical WMH were coded separately. Subjects with bipolar disorder had greater prevalence of WMH abnormalities than comparison subjects (Bipolar, grade 1 = 11.6%, grade 2 = 9.3%, grade 3 = 7.0%; Comparison, grade 1 = 5.1%, grade 2 = 2.6%, grade 3 = 0%). This difference is mainly due to the differences in deep WMH (Bipolar, grade 1 = 14.0%, grade 2 = 14.0%; Comparison, grade 1 = 7.7%, grade 2 = 0%). The current study confirms the higher prevalence of WMH in subjects with bipolar disorder. Differences of small-sized WMH abnormalities between groups were successfully detected using a large number of bipolar subjects and thinner sliced MR images with FLAIR.

Joint hypermobility syndrome and mitral valve prolapse in panic disorder

OBJECTIVE

The purpose of this study is to test the association between joint hypermobility syndrome (JHS) and panic disorder (PD) and to determine whether mitral valve prolapse (MVP) modifies or accounts in part for the association.

METHOD

A total of 115 subjects are included in this study in three groups. Group I (n = 42): panic disorder patients with MVP. Group II (n = 35): panic disorder patients without mitral valve prolapse. Group III (n = 38): control subjects who had mitral valve prolapse without any psychiatric illness. Beighton criteria were used to assess joint hypermobility syndrome. Two-dimensional and M-mode echocardiography was performed on each subject to detect mitral valve prolapse.

RESULTS

Joint hypermobility syndrome was found in 59.5% of panic disorder patients with mitral valve prolapse, in 42.9% of patients without mitral valve prolapse and in 52.6% of control subjects. Beighton scores was 4.93 +/- 2.97 in group I, 4.09 +/- 2.33 in group II, and 4.08 +/- 2.34 in group III. There was no significant difference between groups according to Beighton scores.

CONCLUSION

We did not detect a statistically significant relationship between panic disorder and joint hypermobility syndrome. Mitral valve prolapse and joint hypermobility syndrome are known to be etiologically related and we suggest that mitral valve prolapse affects the prevalence of joint hypermobility syndrome in the panic disorder patients.

White matter hyperintensities in subjects with cocaine and opiate dependence and healthy comparison subjects

The prevalence, severity, and location of white matter signal hyperintensities (WMH) on brain magnetic resonance images were compared in patients with cocaine or opiate dependence and healthy subjects. Patients with cocaine (n=32) and opiate dependence (n=32), whose diagnoses were confirmed with the Structured Clinical Interview for DSM-IV, and age- and sex-matched healthy subjects (n=32) were scanned using a 1.5 T whole body GE magnetic resonance scanner. Axial proton-density and T2-weighted images were obtained as well as fluid-attenuated inversion recovery axial images. The severity of WMH was assessed separately for deep (and insular) and periventricular WMH, using a modified composite version of the rating scales of Fazekas and Coffey. The cocaine-dependent group had greater severity of WMH than the opiate-dependent group, which in turn had greater severity of WMH than the healthy comparison group (odds ratios=2.54 and 2.90, respectively). The cocaine-dependent group had greater lesion severity of deep and insular WMH than the opiate-dependent group and the healthy comparison group (odds ratio>3.25 for deep WMH; odds ratio>4.38 for insular WMH). For periventricular WMH, there were no significant differences between the three groups. The frontal lobes were the predominant locations of WMH in both substance-dependent groups. The greater prevalence and severity of WMH in cocaine-dependent subjects than in opiate-dependent subjects may reflect the fact that cocaine induces more ischemia via vasoconstriction than opiates. Also, there was a trend for lower WMH severity in substance-dependent women relative to the healthy comparison group, possibly due to estrogen's protective effect against cerebrovascular accidents.

Epilepsy and anxiety

Studies in the general population demonstrate that anxiety disorders are associated with impaired quality of life and function. Available evidence suggests that comorbid anxiety disorders are frequent among patients with epilepsy but that neither the interrelationships between them nor the impact of anxiety disorders on functional outcome is well studied. The study and management of anxiety disorders are further complicated by the occurrence of seizures, the temporal relationship between seizures and anxiety symptoms/syndromes, and the influence of antiepileptic drugs. Increased recognition of anxiety disorders among patients with epilepsy and evaluation of the potential impact of these disorders on functional outcome and the beneficial and detrimental effects of antiepileptic drugs in clinical practice are needed.

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.

Decreased left temporal lobe volume of panic patients measured by magnetic resonance imaging

Reported neuroimaging studies have shown functional and morphological changes of temporal lobe structures in panic patients, but only one used a volumetric method. The aim of the present study was to determine the volume of temporal lobe structures in patients with panic disorder, measured by magnetic resonance imaging. Eleven panic patients and eleven controls matched for age, sex, handedness, socioeconomic status and years of education participated in the study. The mean volume of the left temporal lobe of panic patients was 9% smaller than that of controls (t21 = 2.37, P = 0.028). In addition, there was a trend (P values between 0.05 and 0.10) to smaller volumes of the right temporal lobe (7%, t21 = 1.99, P = 0.06), right amygdala (8%, t21 = 1.83, P = 0.08), left amygdala (5%, t21 = 1.78, P = 0.09) and left hippocampus (9%, t21 = 1.93, P = 0.07) in panic patients compared to controls. There was a positive correlation between left hippocampal volume and duration of panic disorder (r = 0.67, P = 0.025), with recent cases showing more reduction than older cases. The present results show that panic patients have a decreased volume of the left temporal lobe and indicate the presence of volumetric abnormalities of temporal lobe structures.

Evaluation of regional cerebral blood flow changes in panic disorder with Tc99m-HMPAO SPECT

The objective of this study is to investigate differences in regional cerebral blood flow (rCBF) and rCBF asymmetry index values between panic disorder patients (n=22) and normal comparison subjects (n=19) using Tc99m-hexamethylpropyleneamine oxime single photon emission tomography imaging. A decrease in perfusion in the bilateral frontal regions and a relative increase in perfusion in the right medial and superior frontal regions were found. There were significant positive correlations between scores on the Panic and Agoraphobia Scale and rCBF asymmetry index values of the parietal, superior temporal and lateral temporal regions in the panic disorder patients. These correlations point to a relationship between the severity of panic disorder and relative right brain activation. Activation of the amygdala, increased CBF in the frontal region, or hyperactivation of the locus ceruleus seen in panic disorder may explain the decrease in the rCBF in the inferior frontal region.

Amygdalar atrophy in panic disorder patients detected by volumetric magnetic resonance imaging

It has been suggested that the pathophysiology of panic disorder (PD) may involve abnormalities in several brain structures, including the amygdala. To date, however, no study has used quantitative structural neuroimaging techniques to examine amygdalar anatomy in this disorder. Volumetric magnetic resonance imaging (MRI) studies of the amygdalas, hippocampi, and temporal lobes were conducted in 12 drug-free, symptomatic PD patients (six females and six males), and 12 case-matched healthy comparison subjects. Volumetric MRI data were normalized for brain size. PD patients were found to have smaller left-sided and right-sided amygdalar volumes than controls. No differences were found in either hippocampi or temporal lobes. These findings provide new evidence of changes in amygdalar structure in PD and warrant further anatomical and MRI brain studies of patients with this disorder.

Effects of acute cholecystokinin infusion on hemispheric EEG asymmetry and coherence in healthy volunteers

This study investigated the effects of continuous slow infusion of cholecystokinin tetrapeptide (CCK-4), a neuropeptide with panicogenic properties, on functional hemispheric differences, as indexed by quantitative electroencephalographic (EEG) asymmetry and coherence measures. Twenty-four adult volunteers (15 females and 9 males) were assigned to infusion with either placebo or CCK-4 in a randomized, double-blind, parallel-group design, with EEG being recorded before and during (10 and 40 min) a 60-min infusion period. No significant treatment differences were observed for absolute EEG power but, compared to placebo, CCK-4 infusion increased asymmetry and reduced coherence of slow-wave activity at midtemporal recording sites. These findings support the contention that functional imbalance of the temporal cortex, perhaps mediated by CCK-4, is involved in panic disorder (PD).

rCBF differences between panic disorder patients and control subjects during anticipatory anxiety and rest

BACKGROUND

Our goal was to identify brain structures involved in anticipatory anxiety in panic disorder (PD) patients compared to control subjects.

METHODS

Seventeen PD patients and 21 healthy control subjects were studied with H(2)(15)O positron emission tomography scan, before and after a pentagastrin challenge.

RESULTS

During anticipatory anxiety we found hypoactivity in the precentral gyrus, the inferior frontal gyrus, the right amygdala, and the anterior insula in PD patients compared to control subjects. Hyperactivity in patients compared to control subjects was observed in the parahippocampal gyrus, the superior temporal lobe, the hypothalamus, the anterior cingulate gyrus, and the midbrain. After the challenge, the patients showed decreases compared to the control subjects in the precentral gyrus, the inferior frontal gyrus, and the anterior insula. Regions of increased activity in the patients compared to the control subjects were the parahippocampal gyrus, the superior temporal lobe, the anterior cingulate gyrus, and the midbrain.

CONCLUSIONS

The pattern of regional cerebral blood flow activations and deactivations we observed both before and after the pentagastrin challenge was the same, although different in intensity. During anticipatory anxiety more voxels were (de)activated than during rest after the challenge.

Reduced levels of creatine in the right medial temporal lobe region of panic disorder patients detected with (1)H magnetic resonance spectroscopy

In vivo proton magnetic resonance spectroscopy ((1)H MRS) was used to study possible neurochemical abnormalities in drug-free, symptomatic panic disorder patients at rest. (1)H MRS was performed in 11 panic disorder patients and 11 healthy age- and sex-matched comparison subjects. Levels of brain metabolites were determined in the right medial temporal lobe region (encompassing the whole amygdala and part of the hippocampus) and in the medial prefrontal cortex on the basis of previous work with both structural and functional neuroimaging techniques. The concentration of creatine and phosphocreatine, metabolites involved in energy-dependent systems in brain, was significantly lower in the right medial temporal lobe region of panic disorder patients compared to healthy subjects. No significant differences between the two groups were observed in the medial prefrontal cortex. These results provide neurochemical evidence suggesting the involvement of the amygdalohippocampal region in the pathogenesis of panic disorder.

Anatomical MRI findings in mood and anxiety disorders

OBJECTIVE

In vivo structural magnetic resonance imaging (MRI) studies have evaluated the brain anatomy of various psychiatric disorders, allowing the investigation of putative abnormal brain circuits possibly involved in the patophysiology of psychiatric disorders. Here we reviewed the structural MRI literature in mood and anxiety disorders.

METHODS

All anatomical MRI studies evaluating mood and anxiety disorder patients were identified through a comprehensive Medline search conducted for the period from 1966 to January 2002, and a manual search of bibliographic cross-referencing complemented the Medline search.

RESULTS

Differential patterns of anatomical brain abnormalities appear to be involved in subtypes of mood disorders, with hippocampus and basal ganglia being abnormal in unipolar disorder, and amygdala and cerebellum in bipolar disorders, suggesting that these two mood disorders are biologically distinct. As for anxiety disorders, orbital frontal regions and basal ganglia have been reported to be anatomically abnormal in obsessive-compulsive disorder, temporal lobe was found to be abnormally reduced in panic disorder, and abnormal hippocampus shrinkage was shown in posttraumatic stress disorder.

CONCLUSIONS

The structural MRI findings reviewed here suggest abnormalities in specific brain regions participating in proposed neuroanatomic models possibly involved in the pathophysiology of mood disorders and anxiety disorders. Nonetheless, available MRI studies have suffered from limitations related to relatively small patient samples and involvement of medicated patients, and were largely cross-sectional investigations. Therefore, longitudinal MRI studies involving more sizeable samples of drug-free patients, patients at first episode of illness or at high risk for mood or anxiety disorders, associated to genetic studies, are likely to be extremely valuable to separate state from trait brain abnormalities and to characterize further the pathophysiology of these disorders.

Central representation of the sympathetic nervous system in the cerebral cortex

The sympathetic-related regions of the cerebral cortex were identified in rats after pseudorabies virus injections were made in functionally different targets: adrenal gland, stellate ganglion which regulates the heart, or celiac ganglion which innervates the gastrointestinal tract. Extensive transneuronal labeling was found in limbic system areas: (1) extended amygdaloid complex, (2) lateral septum, and (3) infralimbic, insular, and ventromedial temporal cortical regions (viz., ectorhinal cortex=Brodmann's area 36, perirhinal cortex=area 35, lateral entorhinal=area 28, and ventral temporal association cortex=Te3 region). Deep temporal lobe structures were prominently labeled, including the amygdalopiriform and amygdalohippocampal transition areas, ventral hippocampus and ventral subiculum. The cortical circuits mediating emotional-autonomic changes (i.e., mind-body control) are discussed.