Insula response to unpredictable and predictable aversiveness in individuals with panic disorder and comorbid depression

Emotion processing in depression with and without comorbid anxiety disorder

BACKGROUND

Among mental disorders, major depressive disorder (MDD) is highly prevalent and associated with emotional dysfunctions linked to activity alterations in the brain, mainly in prefrontal regions, the insula, the anterior cingulate cortex and the amygdala. However, this evidence is heterogeneous, perhaps because magnetic resonance imaging (MRI) studies on MDD tend to neglect comorbid anxiety (COM-A).

METHODS

To address this, here a sample of age- and sex-matched patients, n_MDD = 90 and n_COM-A = 85, underwent functional MRI to assess neurofunctional group differences during a negative emotional face-matching task using a hypothesis-driven region of interest approach (dorsolateral prefrontal cortex, insula, anterior cingulate cortex, amygdala) and an explorative whole-brain approach. We also assessed these relationships with state-trait anxiety measures, a state depression measure, general functioning and medication load.

RESULTS

During face processing, COM-A (compared to MDD) had significantly increased bilateral insula activity. No activity differences were found in the anterior cingulate cortex or the amygdala. Whole-brain analyses revealed increased inferior temporal activation and frontal activation (comprising the inferior and middle frontal gyrus) in COM-A that was positively linked to state anxiety as well as general functioning across groups.

LIMITATIONS

Still, the lack of a healthy control and small effects mean this study should be replicated to further interpret the results.

CONCLUSIONS

The findings highlight a discriminative activation pattern between MDD and COM-A regarding emotion processing and may present a correlate of potentially anxiety-related psychopathology. In future, further investigations in potential discriminative activity patterns could help to elucidate the origin, development and treatment of depression.

The neurobiology of misophonia and implications for novel, neuroscience-driven interventions

Decreased tolerance in response to specific every-day sounds (misophonia) is a serious, debilitating disorder that is gaining rapid recognition within the mental health community. Emerging research findings suggest that misophonia may have a unique neural signature. Specifically, when examining responses to misophonic trigger sounds, differences emerge at a physiological and neural level from potentially overlapping psychopathologies. While these findings are preliminary and in need of replication, they support the hypothesis that misophonia is a unique disorder. In this theoretical paper, we begin by reviewing the candidate networks that may be at play in this complex disorder (e.g., regulatory, sensory, and auditory). We then summarize current neuroimaging findings in misophonia and present areas of overlap and divergence from other mental health disorders that are hypothesized to co-occur with misophonia (e.g., obsessive compulsive disorder). Future studies needed to further our understanding of the neuroscience of misophonia will also be discussed. Next, we introduce the potential of neurostimulation as a tool to treat neural dysfunction in misophonia. We describe how neurostimulation research has led to novel interventions in psychiatric disorders, targeting regions that may also be relevant to misophonia. The paper is concluded by presenting several options for how neurostimulation interventions for misophonia could be crafted.

Association between startle reactivity to uncertain threats and structural brain volume

Sensitivity to uncertain threat (U-threat) is a clinically important individual difference factor in multiple psychopathologies. Recent studies have implicated a specific frontolimbic circuit as a key network involved in the anticipation of aversive stimuli. In particular, the insula, thalamus, and dorsal anterior cingulate cortex (dACC) have recently been found to be robustly activated by anticipation of U-threat. However, no study to date has examined the association between U-threat reactivity and structural brain volume. In the present study, we utilized a pooled sample of 186 young adult volunteers who completed a structural MRI scan and the well-validated No-Predictable-Unpredictable (NPU) threat of electric shock task. Startle eyeblink potentiation was collected during the NPU task as an objective index of aversive reactivity. ROI-based analyses revealed that increased startle reactivity to U-threat was associated with reduced gray matter volume in the right insula and bilateral thalamus, but not the dACC. These results add to a growing literature implicating the insula and thalamus as core nodes involved in individual differences in U-threat reactivity.

Systematic transdiagnostic review of magnetic-resonance imaging results: Depression, anxiety disorders and their co-occurrence

BACKGROUND

Major depressive disorder (MDD) and anxiety disorders (ANX) share core symptoms such as negative affect and often co-exist. Magnetic-resonance imaging (MRI) research suggests shared neuroanatomical/neurofunctional underpinnings. So far, studies considering transdiagnostic and disorder-specific neural alterations in MDD and ANX as well as the comorbid condition (COM) have not been reviewed systematically.

METHODS

Following PRISMA guidelines, the literature was screened and N = 247 articles were checked according to the PICOS criteria: MRI studies investigating transdiagnostic (across MDD, ANX, COM compared to healthy controls) and/or disorder-specific (between MDD, ANX, COM) neural alterations. N = 35, thereof n = 13 structural MRI and diffusion-tensor imaging studies and n = 22 functional MRI studies investigating emotional, cognitive deficits and resting state were included and quality coded.

RESULTS

Results indicated transdiagnostic structural/functional alterations in the orbitofrontal cortex/middle frontal cortex and in limbic regions (amygdala, cingulum, hippocampus). Few and inconsistent disorder-specific alterations were reported. However, depression-specific functional alterations were reported for the inferior frontal gyrus and dorsolateral prefrontal cortex during emotional tasks, and limbic regions at rest. Preliminary results for anxiety-specific functional alterations were found in the insula and frontal regions during emotional tasks, in the inferior parietal lobule, superior frontal gyrus and superior temporal gyrus during cognitive tasks, and (para)limbic alterations at rest.

CONCLUSIONS

This review provides evidence to support existing transdiagnostic fronto-limbic neural models in MDD and ANX. On top, it expands existing knowledge taking into account comorbidity and comparing MDD with ANX. Heterogeneous evidence exists for disorder-specific alterations. Research focusing on ANX sub-types, and the consideration of COM would contribute to a better understanding of basic neural underpinnings.

Startle during threat longitudinally predicts functional impairment independent of DSM diagnoses

Heightened responsivity to unpredictable, and perhaps predictable, threat characterizes some internalizing disorders and may be vulnerability factors for psychopathology as well. However, few studies have directly tested whether individual differences in unpredictable and/or predictable threat responding longitudinally predict symptoms of psychopathology and functional outcomes. Examining functioning is particularly important given that functioning is separable from symptoms of psychopathology. The present study examined whether electromyography startle measures of predictable and/or unpredictable threat responding was associated with interviewer-assessed symptoms of internalizing psychopathology and functional impairment at baseline (n = 409) and one-year follow-up (n = 104). Elevated startle responding to unpredictable and predictable threat longitudinally predicted a worsening of functioning over time and this effect was independent of change of symptoms over time. Importantly, threat responding at baseline predicted functional impairment during the follow-up independent of the effects of DSM-defined fear-based (e.g., panic disorder) or distress-misery (e.g., major depressive disorder) internalizing disorders. These findings provide initial support for the incremental validity of neurobiological vulnerability markers of threat responding over and above DSM disorders and highlight the importance of distinguishing functional outcomes from symptom outcomes.

Neural correlates of predictable and unpredictable threat in internalizing psychopathology

Converging lines of evidence suggest that heightened responding to unpredictable threat may be an important neurobiological marker of internalizing psychopathology (IP). Prior data also indicate that aversive responding to uncertainty may be mediated by hyperactivation of several brain regions within the frontolimbic circuit, namely the anterior insula (aINS) and the dorsal anterior cingulate cortex (dACC). To date, however, the majority of this research has been focused on individual diagnoses and it is unclear whether abnormal neural reactivity to unpredictable threat is observed within heterogeneous, transdiagnostic IP patient populations, as theory would suggest. The aim of the current study was to therefore examine the neural correlates of temporally unpredictable (U) and predictable (P) threat in a sample of healthy controls (n = 24) and patients with a broad range of IP diagnoses (n = 51). We also examined whether symptom severity measures of fear and distress/misery dimensions correlated with neural reactivity to U- and P-threat. All participants completed a modified version of a well-validated threat-of-shock task during functional magnetic resonance imaging (fMRI). Across all participants, U- and P-threat elicited heightened activation in the aINS and brainstem, while P-threat alone also activated the dACC. Relative to healthy controls, patients displayed greater activation in the right aINS during U-threat, and greater right brainstem activation during P-threat. In addition, we found that brainstem activity during U-threat correlated with fear, but not distress/misery, psychopathology. Taken together, these preliminary results suggest that exaggerated aINS reactivity during U-threat and brainstem reactivity during P-threat may have the potential to become important transdiagnostic biomarkers of IP; however, future research efforts are needed to corroborate and expand the present findings.

Fear Network Model in Panic Disorder: The Past and the Future

The core concept for pathophysiology in panic disorder (PD) is the fear network model (FNM). The alterations in FNM might be linked with disturbances in the autonomic nervous system (ANS), which is a common phenomenon in PD. The traditional FNM included the frontal and limbic regions, which were dysregulated in the feedback mechanism for cognitive control of frontal lobe over the primitive response of limbic system. The exaggerated responses of limbic system are also associated with dysregulation in the neurotransmitter system. The neuroimaging studies also corresponded to FNM concept. However, more extended areas of FNM have been discovered in recent imaging studies, such as sensory regions of occipital, parietal cortex and temporal cortex and insula. The insula might integrate the filtered sensory information via thalamus from the visuospatial and other sensory modalities related to occipital, parietal and temporal lobes. In this review article, the traditional and advanced FNM would be discussed. I would also focus on the current evidences of insula, temporal, parietal and occipital lobes in the pathophysiology. In addition, the white matter and functional connectome studies would be reviewed to support the concept of advanced FNM. An emerging dysregulation model of fronto-limbic-insula and temporooccipito-parietal areas might be revealed according to the combined results of recent neuroimaging studies. The future delineation of advanced FNM model can be beneficial from more extensive and advanced studies focusing on the additional sensory regions of occipital, parietal and temporal cortex to confirm the role of advanced FNM in the pathophysiology of PD.

Neural hypersensitivity to pleasant touch in women remitted from anorexia nervosa

Interoception, or the sensing and integration of bodily state signals, has been implicated in anorexia nervosa (AN), given that the hallmark symptoms involve food restriction and body image disturbance. Here we focus on brain response to the anticipation and experience of affective interoceptive stimuli. Women remitted from AN (RAN; N = 18) and healthy comparison women (CW; N = 26) underwent a pleasant affective touch paradigm consisting of gentle strokes with a soft brush administered to the forearm or palm during functional neuroimaging. RAN had a lower brain response relative to CW during anticipation of touch, but a greater response when experiencing touch in the right ventral mid-insula. In RAN, this reduced anticipatory response was associated with higher levels of harm avoidance. Exploratory analyses in RAN also suggested that lower response during touch anticipation was associated with greater body dissatisfaction and higher perceived touch intensity ratings. This reduced responsivity to the anticipation of pleasant affective interoceptive stimuli in association with higher harm avoidance, along with an elevated response to the experience of touch, suggests an impaired ability in AN to predict and interpret incoming physiological stimuli. Impaired interoception may thus impact one's sense of self, thereby supporting observations of disturbed body image and avoidance of affective and social stimuli. Therapeutic approaches that help AN to better anticipate and interpret salient affective stimuli or improve tolerance of interoceptive experiences may be an important addition to current interventions.

Toward an Embodied Medicine: A Portable Device with Programmable Interoceptive Stimulation for Heart Rate Variability Enhancement

In this paper, we describe and test a new portable device that is able to deliver tactile interoceptive stimulation. The device works by delivering precise interoceptive parasympathetic stimuli to C-tactile afferents connected to the lamina I spinothalamocortical system. In humans, interoceptive stimulation can be used to enhance heart rate variability (HRV). To test the effectiveness of the device in enhancing HRV, 13 subjects were randomly assigned in a single-blind between-subjects design either to the experimental condition or to the control condition. In the experimental condition, subjects received stimulation with the developed device; in the control condition subjects received stimulation with static non-interoceptive pressure. Subjects’ electrocardiograms (ECG) were recorded, with sampling at 1000 Hz for 5 min as a baseline, and then during the stimulations (11 min). Time domain analyses were performed to estimate the short-term vagally mediated component (rMSSD) of HRV. Results indicated that the experimental group showed enhanced rMSSD, compared to the control group. Moreover, frequency domain analyses indicated that high frequency band power, which reflects parasympathetic activity in humans, also appeared to be enhanced in the experimental group compared to control subjects. Conclusions and future challenges for an embodied perspective of rehabilitative medicine are discussed.

Acute calming effects of alcohol are associated with disruption of the salience network

The mood-altering properties of alcohol are a key motivation for drinking, and people commonly report that they drink alcohol to alleviate stress or to relax. To date, the neural processes associated with the self-reported calming effects of alcohol are not well understood. Existing data imply that alcohol may target and disrupt activity within anterior insula (aINS) and amygdala-based neural networks, which are regions implicated in threat detection and anxious responding. The aims of the current study were (1) to examine the acute effect of alcohol upon functional connectivity within aINS and amygdala circuits and (2) to assess relationships between alcohol effects on functional connectivity and self-reported subjective mood. Healthy men and women (N = 39) who reported regular binge drinking completed a within-subjects, double-blind, placebo-controlled pharmacological functional magnetic resonance imaging experiment with i.v. infusions of either alcohol or placebo. Infusion profiles were personalized for each participant and raised breath alcohol concentration to 80 mg percent. Before, during and after infusions, participants rated their subjective mood (stimulation, sedation and calm). Results showed that alcohol dampened functional connectivity between bilateral aINS seed-regions-of-interest and the dorsal anterior cingulate cortex (dACC), key nodes of the salience network. Additionally, the more that alcohol reduced right aINS-dACC functional connectivity, the calmer participants felt during alcohol administration. Alcohol had no effect on amygdala functional connectivity. These findings suggest that alcohol disrupts aINS-dACC functional connectivity, which may impair detection and appraisal of emotionally salient information and relate to acute relaxing effects of the drug.

Brain abnormalities in cognition, anxiety, and depression regulatory regions in adolescents with single ventricle heart disease

BACKGROUND

Single ventricle heart disease (SVHD) adolescents show cognitive impairments and anxiety and depressive symptoms, indicating the possibility of brain injury in regions that control these functions. However, brain tissue integrity in cognition, anxiety, and depression regulatory sites in SVHD remains unclear. We examined brain tissue changes in SVHD compared to controls using T2-relaxometry procedures, which measure free water content and show tissue injury.

METHODS

Proton-density and T2-weighted images, using a 3.0-Tesla MRI, as well as anxiety (Beck anxiety inventory [BAI]), depressive symptoms (patient health questionnaire-9 [PHQ-9]), and cognition (wide range assessment of memory and learning 2 [WRAML2] and Montreal cognitive assessment [MoCA]) data were collected from 20 SVHD (age: 15.8 ± 1.1 years, male/female: 11/9) and 36 controls (age: 16.0 ± 1.1 years, male/female: 19/17). Whole-brain T2-relaxation maps were calculated, normalized to a common space, smoothed, and compared between groups and sexes (analysis of covariance; covariates: age, sex; p < 0.001).

RESULTS

SVHD subjects showed significantly increased BAI and PHQ-9 and reduced MoCA and WRAML2 scores over controls. Several brain regions in SVHD showed increased T2-relaxation values (chronic injury), including the cingulate, and insula, hippocampus/para-hippocampal gyrus, thalamus, hypothalamus, amygdala, frontal white matter, corpus callosum, brainstem, and cerebellar areas. Decreased T2-relaxation values (acute injury) emerged in a few regions, including the prefrontal and cerebellar cortices in SVHD over controls. In addition, male SVHD showed more brain changes over female SVHD.

CONCLUSIONS

Adolescents with SVHD showed significant brain injury with variable male-female differences in areas that control cognition, anxiety, and depression, which may contribute to functional deficits found in the condition.

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.

Distinct phasic and sustained brain responses and connectivity of amygdala and bed nucleus of the stria terminalis during threat anticipation in panic disorder

BACKGROUND

Panic disorder (PD) patients are constantly concerned about future panic attacks and exhibit general hypersensitivity to unpredictable threat. We aimed to reveal phasic and sustained brain responses and functional connectivity of the amygdala and the bed nucleus of the stria terminalis (BNST) during threat anticipation in PD.

METHODS

Using functional magnetic resonance imaging (fMRI), we investigated 17 PD patients and 19 healthy controls (HC) during anticipation of temporally unpredictable aversive and neutral sounds. We used a phasic and sustained analysis model to disentangle temporally dissociable brain activations.

RESULTS

PD patients compared with HC showed phasic amygdala and sustained BNST responses during anticipation of aversive v. neutral stimuli. Furthermore, increased phasic activation was observed in anterior cingulate cortex (ACC), insula and prefrontal cortex (PFC). Insula and PFC also showed sustained activation. Functional connectivity analyses revealed partly distinct phasic and sustained networks.

CONCLUSIONS

We demonstrate a role for the BNST during unpredictable threat anticipation in PD and provide first evidence for dissociation between phasic amygdala and sustained BNST activation and their functional connectivity. In line with a hypersensitivity to uncertainty in PD, our results suggest time-dependent involvement of brain regions related to fear and anxiety.

Reactivity to unpredictable threat as a treatment target for fear-based anxiety disorders

BACKGROUND

Heightened reactivity to unpredictable threat (U-threat) is a core individual difference factor underlying fear-based psychopathology. Little is known, however, about whether reactivity to U-threat is a stable marker of fear-based psychopathology or if it is malleable to treatment. The aim of the current study was to address this question by examining differences in reactivity to U-threat within patients before and after 12-weeks of selective serotonin reuptake inhibitors (SSRIs) or cognitive-behavioral therapy (CBT).

METHODS

Participants included patients with principal fear (n = 22) and distress/misery disorders (n = 29), and a group of healthy controls (n = 21) assessed 12-weeks apart. A well-validated threat-of-shock task was used to probe reactivity to predictable (P-) and U-threat and startle eyeblink magnitude was recorded as an index of defensive responding.

RESULTS

Across both assessments, individuals with fear-based disorders displayed greater startle magnitude to U-threat relative to healthy controls and distress/misery patients (who did not differ). From pre- to post-treatment, startle magnitude during U-threat decreased only within the fear patients who received CBT. Moreover, within fear patients, the magnitude of decline in startle to U-threat correlated with the magnitude of decline in fear symptoms. For the healthy controls, startle to U-threat across the two time points was highly reliable and stable.

CONCLUSIONS

Together, these results indicate that startle to U-threat characterizes fear disorder patients and is malleable to treatment with CBT but not SSRIs within fear patients. Startle to U-threat may therefore reflect an objective, psychophysiological indicator of fear disorder status and CBT treatment response.

Functional neuroanatomy in panic disorder: Status quo of the research

AIM

To provide an overview of the current research in the functional neuroanatomy of panic disorder.

METHODS

Panic disorder (PD) is a frequent psychiatric disease. Gorman et al (1989; 2000) proposed a comprehensive neuroanatomical model of PD, which suggested that fear- and anxiety-related responses are mediated by a so-called “fear network” which is centered in the amygdala and includes the hippocampus, thalamus, hypothalamus, periaqueductal gray region, locus coeruleus and other brainstem sites. We performed a systematic search by the electronic database PubMed. Thereby, the main focus was laid on recent neurofunctional, neurostructural, and neurochemical studies (from the period between January 2012 and April 2016). Within this frame, special attention was given to the emerging field of imaging genetics.

RESULTS

We noted that many neuroimaging studies have reinforced the role of the “fear network” regions in the pathophysiology of panic disorder. However, recent functional studies suggest abnormal activation mainly in an extended fear network comprising brainstem, anterior and midcingulate cortex (ACC and MCC), insula, and lateral as well as medial parts of the prefrontal cortex. Interestingly, differences in the amygdala activation were not as consistently reported as one would predict from the hypothesis of Gorman et al (2000). Indeed, amygdala hyperactivation seems to strongly depend on stimuli and experimental paradigms, sample heterogeneity and size, as well as on limitations of neuroimaging techniques. Advanced neurochemical studies have substantiated the major role of serotonergic, noradrenergic and glutamatergic neurotransmission in the pathophysiology of PD. However, alterations of GABAergic function in PD are still a matter of debate and also their specificity remains questionable. A promising new research approach is “imaging genetics”. Imaging genetic studies are designed to evaluate the impact of genetic variations (polymorphisms) on cerebral function in regions critical for PD. Most recently, imaging genetic studies have not only confirmed the importance of serotonergic and noradrenergic transmission in the etiology of PD but also indicated the significance of neuropeptide S receptor, CRH receptor, human TransMEMbrane protein (TMEM123D), and amiloride-sensitive cation channel 2 (ACCN2) genes.

CONCLUSION

In light of these findings it is conceivable that in the near future this research will lead to the development of clinically useful tools like predictive biomarkers or novel treatment options.

Association between neural reactivity and startle reactivity to uncertain threat in two independent samples

Prior studies indicate that anxiety disorders are associated with heightened sensitivity to uncertain threat (U threat). Individual differences in reactivity to U threat have been measured in the laboratory with two methodologies-startle eyeblink potentiation and fMRI. While startle and fMRI are purported to relate to each other, very little research exists on whether individual differences in one measure are associated with individual differences in another and, thus, whether startle and fMRI capture shared mechanisms. Therefore, the current study was designed to investigate if and where in the brain measures of startle potentiation and fMRI BOLD signal correlate during response to U threat across two independent samples. Participants in both studies completed two threat anticipation tasks-once during collection of startle potentiation and once during fMRI. In Study 1 (n = 43), the startle and fMRI tasks both used electric shock as the threat. As an extension, in Study 2 (n = 38), the startle task used electric shock but the fMRI task used aversive images. Despite these methodological differences, greater startle potentiation to U threat was associated with greater dorsal anterior cingulate, caudate, and orbitofrontal cortex reactivity to U threat in both samples. The findings suggest that startle and fMRI measures of responding to U threat overlap, and points toward an integrated brain-behavior profile of aberrant U threat responding.

Startle potentiation to uncertain threat as a psychophysiological indicator of fear-based psychopathology: An examination across multiple internalizing disorders

Heightened reactivity to uncertain threat (U-threat) is an important individual difference factor that may characterize fear-based internalizing psychopathologies (IPs) and distinguish them from distress/misery IPs. To date, however, the majority of existing research examining reactivity to U-threat has been within individuals with panic disorder and major depressive disorder (MDD) and no prior study has directly tested this hypothesis across multiple IPs. The current study therefore explored whether heightened reactivity to U-threat is a psychophysiological indicator of fear-based psychopathology across 5 groups: current (a) social anxiety disorder (SAD); (b) specific phobia (SP); (c) generalized anxiety disorder (GAD); (d) MDD; and (c) individuals with no history of psychopathology (controls). All 160 adults completed a well-validated threat-of-shock task designed to probe responses to predictable (P-) and U-threat. Startle eyeblink potentiation was recorded as an index of aversive arousal. Results indicated that individuals with SAD and SP evidenced greater startle potentiation to U-threat, but not P-threat, relative to individuals with GAD, MDD, and controls (who did not differ). The current findings, along with the prior panic disorder and MDD literature, suggest that heightened reactivity to U-threat is a psychophysiological indicator of fear-based disorders and could represent a neurobiological organizing principle for internalizing psychopathology. The findings also suggest that individuals with fear disorders generally display a hypersensitivity to uncertain aversive events, which could contribute to their psychopathology. (PsycINFO Database Record

Impact of Panic on Psychophysiological and Neural Reactivity to Unpredictable Threat in Depression and Anxiety

Exaggerated anxious responding to unpredictable threat (U-threat) is a core feature of panic disorder (PD). However, it is unknown whether this abnormality is specific to the diagnosis of PD or would manifest along a continuum of panic symptomatology (PS). Additionally, little is known about the neural processes underlying this abnormality among those high in PS. Finally, no studies have tested whether startle potentiation and limbic neural reactivity - commonly used indices of U-threat responsivity - are associated and therefore reflect common abnormalities. These questions were investigated in 42 adults with a range of PS. U-threat responding was measured twice during threat-of-shock - once with startle and once with functional magnetic resonance imaging (fMRI). As hypothesized, PS positively predicted startle potentiation and dACC reactivity to U-threat. Startle potentiation and dACC activation to U-threat were positively associated. These results suggest a biobehavioral profile of aberrant responding to U-threat associated with PS.

Functional MRI activation in response to panic-specific, non-panic aversive, and neutral pictures in patients with panic disorder and healthy controls

There is evidence that besides limbic brain structures, prefrontal and insular cortical activations and deactivations are involved in the pathophysiology of panic disorder. This study investigated activation response patterns to stimulation with individually selected panic-specific pictures in patients with panic disorder with agoraphobia (PDA) and healthy control subjects using functional magnetic resonance imaging (fMRI). Structures of interest were the prefrontal, cingulate, and insular cortex, and the amygdalo-hippocampal complex. Nineteen PDA subjects (10 females, 9 males) and 21 healthy matched controls were investigated using a Siemens 3-Tesla scanner. First, PDA subjects gave Self-Assessment Manikin (SAM) ratings on 120 pictures showing characteristic panic/agoraphobia situations, of which 20 pictures with the individually highest SAM ratings were selected. Twenty matched pictures showing aversive but not panic-specific stimuli and 80 neutral pictures from the International Affective Picture System were chosen for each subject as controls. Each picture was shown twice in each of four subsequent blocks. Anxiety and depression ratings were recorded before and after the experiment. Group comparisons revealed a significantly greater activation in PDA patients than control subjects in the insular cortices, left inferior frontal gyrus, dorsomedial prefrontal cortex, the left hippocampal formation, and left caudatum, when PA and N responses were compared. Comparisons for stimulation with unspecific aversive pictures showed activation of similar brain regions in both groups. Results indicate region-specific activations to panic-specific picture stimulation in PDA patients. They also imply dysfunctionality in the processing of interoceptive cues in PDA and the regulation of negative emotionality. Therefore, differences in the functional networks between PDA patients and control subjects should be further investigated.

Altered brain responses in subjects with irritable bowel syndrome during cued and uncued pain expectation

BACKGROUND

A majority of the subjects with irritable bowel syndrome (IBS) show increased behavioral and brain responses to expected and delivered aversive visceral stimuli during controlled rectal balloon distension, and during palpation of the sigmoid colon. We aimed to determine if altered brain responses to cued and uncued pain expectation are also seen in the context of a noxious somatic pain stimulus applied to the same dermatome as the sigmoid colon.

METHODS

A task-dependent functional magnetic resonance imaging technique was used to investigate the brain activity of 37 healthy controls (18 females) and 37 IBS subjects (21 females) during: (i) a cued expectation of an electric shock to the abdomen vs a cued safe condition; and (ii) an uncued cross-hair condition in which the threat is primarily based on context vs a cued safe condition.

KEY RESULTS

Regions within the salience, attention, default mode, and emotional arousal networks were more activated by the cued abdominal threat condition and the uncued condition than in the cued safe condition. During the uncued condition contrasted to the cued safe condition, IBS subjects (compared to healthy control subjects) showed greater brain activations in the affective (amygdala, anterior insula) and attentional (middle frontal gyrus) regions, and in the thalamus and precuneus. These disease-related differences were primarily seen in female subjects.

CONCLUSIONS & INFERENCES

The observed greater engagement of cognitive and emotional brain networks in IBS subjects during contextual threat may reflect the propensity of IBS subjects to overestimate the likelihood and severity of future abdominal pain.