Extinction deficit and fear reinstatement after electrical stimulation of the amygdala: implications for kindling-associated fear and anxiety

Interaction of Temporal Lobe Epilepsy and Posttraumatic Stress Disorder: Network Analysis of a Single Case

In this case study, we present a 21 years old female with long-standing Temporal Lobe Epilepsy (TLE) who, following a sexual assault, also developed Posttraumatic Stress Disorder (PTSD), leading to a change in her seizure semiology. The new seizures seemed to be a re-enactment of the sexual assault and accordingly were at first thought to be Psychogenic Non-Epileptic Seizures (PNES). Nevertheless, electroencephalography (EEG) recording at the Epilepsy Monitoring Unit (EMU) revealed ictal epileptic brain activity during these new attacks. In order to further explore the nature of the relation between epileptic seizures and PTSD symptomatology, a functional MRI (fMRI) scan was conducted focusing on neural response to threat (fearful faces). The results indicated that the response to threat elicited bilateral amygdala activation, as well as enhanced amygdala connectivity with the insula and anterior cingulate cortex (ACC), all central nodes of the fear circuitry. Accordingly, we suggest that this unique presentation of "pseudo" PNES might stem from the anatomical proximity of the epileptic network in this patient (temporal-insular-frontal) to the fear circuitry, allowing abnormal epileptic activity to "exploit" or activate the fear circuit or vice versa. We further propose that the traumatic experience may have changed the patient's ictal semiology by modifying the course of the spread of the ictal activity toward the PTSD network.

Ketamine and neuroticism: a double-hit hypothesis of internalizing disorders

Psychiatric disorders can often be viewed as extremes of personality traits. The primary action of drugs that ameliorate these disorders may, thus, be to alter the patient’s position on a relevant trait dimension. Here, we suggest that interactions between such trait dimensions may also be important for disorder. Internalizing disorders show important differences in terms of range of activity and speed of response of medications. Established antidepressant and anxiolytic medications are slow in onset and have differing effects across different internalizing disorders. In contrast, low-dose ketamine is rapidly effective and improves symptom ratings in all internalizing disorders. To account for this, we propose a “double hit” model for internalizing disorders: generation (and maintenance) require two distinct forms of neural dysfunction to coincide. One hit, sensitive to ketamine, is disorder-general: dysfunction of a neural system linked to high levels of the personality trait of neuroticism. The other hit is disorder-specific: dysfunction of one of a set of disorder-specific neural modules, each with its own particular pattern of sensitivity to conventional drugs. Our hypothesis applies only to internalizing disorders. So, we predict that ketamine will be effective in simple phobia and (perhaps partially) in anorexia nervosa, but would make no such prediction about other disorders where neuroticism might also be important secondarily (e.g. attention deficit hyperactivity disorder and schizophrenia).

Common neurocircuitry mediating drug and fear relapse in preclinical models

BACKGROUND

Comorbidity of anxiety disorders, stressor- and trauma-related disorders, and substance use disorders is extremely common. Moreover, therapies that reduce pathological fear and anxiety on the one hand, and drug-seeking on the other, often prove short-lived and are susceptible to relapse. Considerable advances have been made in the study of the neurobiology of both aversive and appetitive extinction, and this work reveals shared neural circuits that contribute to both the suppression and relapse of conditioned responses associated with trauma or drug use.

OBJECTIVES

The goal of this review is to identify common neural circuits and mechanisms underlying relapse across domains of addiction biology and aversive learning in preclinical animal models. We focus primarily on neural circuits engaged during the expression of relapse.

KEY FINDINGS

After extinction, brain circuits involving the medial prefrontal cortex and hippocampus come to regulate the expression of conditioned responses by the amygdala, bed nucleus of the stria terminalis, and nucleus accumbens. During relapse, hippocampal projections to the prefrontal cortex inhibit the retrieval of extinction memories resulting in a loss of inhibitory control over fear- and drug-associated conditional responding.

CONCLUSIONS

The overlapping brain systems for both fear and drug memories may explain the co-occurrence of fear and drug-seeking behaviors.

Establishment of a rat model of ulcerative colitis with abnormal sapra syndrome of traditional Uyghur medicine and detection of changes in inflammation related factors in colon tissue of this model

AIM

To develop a rat model of ulcerative colitis (UC) with abnormal sapra syndrome and detect the changes in inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) hnRNA and mRNA expression in colon tissues of this model.

METHODS

Based on a rat model of abnormal sapra syndrome, trinitrobenzene sulfonic acid/ethanol was used to induce UC in rats with abnormal sapra syndrome. Rats were randomly divided into two groups: normal group and UC with abnormal sapra syndrome model group. Quantitative RT-PCR was used to detect the differences in iNOS and eNOS hnRNA and mRNA expression in colon tissues of rats in the two groups.

RESULTS

UC with abnormal sapra syndrome was successfully induced as evidenced by the presence of anticipated signs, symptoms and colonic mucosa damage. Compared with the normal group, the expression of iNOS hnRNA in colon tissue was significantly upregulated in the model group (P < 0.05), but the expression of eNOS hnRNA in colon tissue showed no statistical difference between the two groups (P > 0.05). The expression of iNOS and eNOS mRNA was significantly upregulated in the model group compared with the normal group (P < 0.05).

CONCLUSION

The inflammatory factors iNOS and eNOS are involved in the development of UC in rats with abnormal sapra syndrome, and changes in inflammation related factors are mediated by a post-transcriptional regulatory mechanism.

Understanding amygdala responsiveness to fearful expressions through the lens of psychopathy and altruism

Because the face is the central focus of human social interactions, emotional facial expressions provide a unique window into the emotional lives of others. They play a particularly important role in fostering empathy, which entails understanding and responding to others' emotions, especially distress-related emotions such as fear. This Review considers how fearful facial as well as vocal and postural expressions are interpreted, with an emphasis on the role of the amygdala. The amygdala may be best known for its role in the acquisition and expression of conditioned fear, but it also supports the perception and recognition of others' fear. Various explanations have been supplied for the amygdala's role in interpreting and responding to fearful expressions. They include theories that amygdala responses to fearful expressions 1) reflect heightened vigilance in response to uncertain danger, 2) promote heightened attention to the eye region of faces, 3) represent a response to an unconditioned aversive stimulus, or 4) reflect the generation of an empathic fear response. Among these, only empathic fear explains why amygdala lesions would impair fear recognition across modalities. Supporting the possibility of a link between fundamental empathic processes and amygdala responses to fear is evidence that impaired fear recognition in psychopathic individuals results from amygdala dysfunction, whereas enhanced fear recognition in altruistic individuals results from enhanced amygdala function. Empathic concern and caring behaviors may be fostered by sensitivity to signs of acute distress in others, which relies on intact functioning of the amygdala.

Myalgic Encephalomyelitis: Symptoms and Biomarkers

Myalgic Encephalomyelitis (ME) continues to cause significant morbidity worldwide with an estimated one million cases in the United States. Hurdles to establishing consensus to achieve accurate evaluation of patients with ME continue, fueled by poor agreement about case definitions, slow progress in development of standardized diagnostic approaches, and issues surrounding research priorities. Because there are other medical problems, such as early MS and Parkinson's Disease, which have some similar clinical presentations, it is critical to accurately diagnose ME to make a differential diagnosis. In this article, we explore and summarize advances in the physiological and neurological approaches to understanding, diagnosing, and treating ME. We identify key areas and approaches to elucidate the core and secondary symptom clusters in ME so as to provide some practical suggestions in evaluation of ME for clinicians and researchers. This review, therefore, represents a synthesis of key discussions in the literature, and has important implications for a better understanding of ME, its biological markers, and diagnostic criteria. There is a clear need for more longitudinal studies in this area with larger data sets, which correct for multiple testing.

A review on human reinstatement studies: an overview and methodological challenges

In human research, studies of return of fear (ROF) phenomena, and reinstatement in particular, began only a decade ago and recently are more widely used, e.g., as outcome measures for fear/extinction memory manipulations (e.g., reconsolidation). As reinstatement research in humans is still in its infancy, providing an overview of its stability and boundary conditions and summarizing methodological challenges is timely to foster fruitful future research. As a translational endeavor, clarifying the circumstances under which (experimental) reinstatement occurs may offer a first step toward understanding relapse as a clinical phenomenon and pave the way for the development of new pharmacological or behavioral ways to prevent ROF. The current state of research does not yet allow pinpointing these circumstances in detail and we hope this review will aid the research field to advance in this direction. As an introduction, we begin with a synopsis of rodent work on reinstatement and theories that have been proposed to explain the findings. The review however mainly focuses on reinstatement in humans. We first describe details and variations of the experimental setup in reinstatement studies in humans and give a general overview of results. We continue with a compilation of possible experimental boundary conditions and end with the role of individual differences and behavioral and/or pharmacological manipulations. Furthermore, we compile important methodological and design details on the published studies in humans and end with open research questions and some important methodological and design recommendations as a guide for future research.

Animal models of fear relapse

Whereas fear memories are rapidly acquired and enduring over time, extinction memories are slow to form and are susceptible to disruption. Consequently, behavioral therapies that involve extinction learning (e.g., exposure therapy) often produce only temporary suppression of fear and anxiety. This review focuses on the factors that are known to influence the relapse of extinguished fear. Several phenomena associated with the return of fear after extinction are discussed, including renewal, spontaneous recovery, reacquisition, and reinstatement. Additionally, this review describes recent work, which has focused on the role of psychological stress in the relapse of extinguished fear. Recent developments in behavioral and pharmacological research are examined in light of treatment of pathological fear in humans.

Reinstatement of extinguished fear by an unextinguished conditional stimulus

Anxiety disorders are often treated using extinction-based exposure therapy, but relapse is common and can occur as a result of reinstatement, whereby an aversive "trigger" can reinstate extinguished fear. Animal models of reinstatement commonly utilize a Pavlovian fear conditioning procedure, in which subjects are first trained to fear a conditional stimulus (CS) by pairing it with an aversive unconditional stimulus (US), and then extinguished by repeated presentations of the CS alone. Reinstatement is typically induced by exposing subjects to an aversive US after extinction, but here we show that exposure to a non-extinguished CS can reinstate conditional fear responding to an extinguished CS, a phenomenon we refer to as "conditional reinstatement" (CRI). Rats were trained to fear two CSs (light and tone) and subsequently underwent extinction training to only one CS (counterbalanced). Presenting the unextinguished CS (but not a novel cue) immediately after extinction reinstated conditional fear responding to the extinguished CS in a test session given 24 h later. These findings indicate that reinstatement of extinguished fear can be triggered by exposure to conditional as well as unconditional aversive stimuli, and this may help to explain why relapse is common following clinical extinction therapy in humans. Further study of CRI using animal models may prove useful for developing refined extinction therapies that are more resistant to reinstatement.

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.

Stereotactic atlas-based depth electrode localization in the human amygdala

BACKGROUND

The efficacy of stereotactic neurosurgery procedures is critically dependent on the accuracy of the device placement procedure. The first step in this process involves correctly identifying the target location in three-dimensional brain space. In some clinical applications, this targeting process cannot be accomplished using MRI images of gross anatomical structures alone. The amygdala complex is a case in point, in that it consists of multiple histologically defined subnuclei with different functional characteristics.

METHODS

In this report, we describe an elastic atlas brain-morphing method that projects amygdala subnuclear anatomical information onto the MRI volumes of individual subjects.

RESULTS

The accuracy of this method was tested in 5 representative subjects using quantitative image-matching analytical techniques. The results demonstrate a high degree of intersubject variability in medial temporal lobe anatomy, and markedly superior anatomical matching performance by the elastic morphing method compared to Affine transformation.

CONCLUSION

Nonlinear elastic morphing technique provides superior performance on fitting atlas templates to individual brain. The strengths and limitations of this and other atlas morphing methods are discussed in the context of emerging functional neurosurgery applications.

Self-Esteem and Autonomic Physiology: Parallels Between Self-Esteem and Cardiac Vagal Tone as Buffers of Threat

In this article a potential physiological connection to self-esteem is suggested: cardiac vagal tone, the degree of influence on the heart by the vagus, a primary nerve of the parasympathetic nervous system. This hypothesis emerges from parallels between the two literatures that suggest both self-esteem and cardiac vagal tone function to provide protection from threat responding. This article reviews these literatures and evidence and preliminary findings that suggest in some contexts self-esteem and cardiac vagal tone may exert an influence on each other. Last, the article discusses theoretical and applied health implications of this potential physiological connection to self-esteem.

Nightmares: A new neurocognitive model

Nightmares are a prevalent parasomnia associated with a range of psychiatric conditions and pathological symptoms. Current knowledge about how nightmares are produced is still influenced by neo-psychoanalytic speculations as well as by more recent personality, evolutionary and neurobiological models. A majority of these models stipulate some type of emotionally adaptive function for dreaming, e.g., image contextualization, affect desomatization, mood regulation or fear extinction. Nightmares are widely seen to be either an intensified expression of an emotionally adaptive function or, conversely, as evidence of its breakdown. Our recent, affective network dysfunction (AND) model, integrates the tenets of many prior models in proposing that nightmares reflect problems with the fear extinction function of dreaming. This new model accounts for a wide range of dysphoric dream imagery (bad dreams, idiopathic nightmares, post-traumatic nightmares) and incorporates recent findings in the areas of brain imaging, sleep physiology, PTSD, anxiety disorders and the consolidation and extinction of fear memories.

Characteristics of extinction of a conditioned passive avoidance reflex in mice with different levels of anxiety

The relationship between the extinction of a conditioned passive avoidance reflex and the initial anxiety level was studied in mice. The time spent in the open arms of an elevated cross maze was used to classify the mice into high-, intermediate-and low-anxiety individuals. Each level of anxiety was found to correspond to a defined extinction dynamic. Highly anxious mice were characterized by the absence of extinction of the conditioned passive avoidance reflex and stability of good reproduction of the memory trace on testing to as long as 15 days. In intermediately anxious individuals, a deficit in performance of the avoidance reflex appeared from day 7 of extinction. In low-anxiety mice, memory trace reproduction deteriorated from test day 11.

The role of the medial prefrontal cortex-amygdala circuit in stress effects on the extinction of fear

Stress exposure, depending on its intensity and duration, affects cognition and learning in an adaptive or maladaptive manner. Studies addressing the effects of stress on cognitive processes have mainly focused on conditioned fear, since it is suggested that fear-motivated learning lies at the root of affective and anxiety disorders. Inhibition of fear-motivated response can be accomplished by experimental extinction of the fearful response to the fear-inducing stimulus. Converging evidence indicates that extinction of fear memory requires plasticity in both the medial prefrontal cortex and the amygdala. These brain areas are also deeply involved in mediating the effects of exposure to stress on memory. Moreover, extensive evidence indicates that gamma-aminobutyric acid (GABA) transmission plays a primary role in the modulation of behavioral sequelae resulting from a stressful experience, and may also partially mediate inhibitory learning during extinction. In this review, we present evidence that exposure to a stressful experience may impair fear extinction and the possible involvement of the GABA system. Impairment of fear extinction learning is particularly important as it may predispose some individuals to the development of posttraumatic stress disorder. We further discuss a possible dysfunction in the medial prefrontal cortex-amygdala circuit following a stressful experience that may explain the impaired extinction caused by exposure to a stressor.

Prior electrical stimulation of dorsal periaqueductal grey matter or deep layers of the superior colliculus sensitizes rats to anxiety-like behaviors in the elevated T-maze test

Electrical stimulation of the dorsal periaqueductal grey matter (DPAG) and deep layers of the superior colliculus (DLSC) of the rat elicits anxiety-like reactions such as freezing and flight. The temporal course of the effects of the aversive electrical stimulation of the DPAG (5, 15 and 30 min afterward) and DLSC (5, 10 and 15 min afterward) on the defensive response of rats exposed to elevated T-maze were determined. The elevated T-maze generates two defensive behaviors, inhibitory avoidance and one-way escape, which have been related, respectively, to generalized anxiety and panic disorders. Prior electrical stimulation of the DPAG (15 min) and DLSC (5 min) enhanced inhibitory avoidance when compared to no-operated and sham animals, although not affecting escape. Therefore, stimulation of the DPAG and DLSC causes a heightened responsivity to anxiogenic stimulus, but not to panicogenic stimulus, inherent to elevated T-maze. These findings support the participation of the DPAG and DLSC in the elaboration of adaptive responses to stressful situations. Besides, the data supports the view that prior electrical stimulation of DPAG and DLSC is selective in sensitizing rats to anxiety-like behaviors, but not to panic-like behaviors in the elevated T-maze test.

Evidence for the perirhinal cortex as a requisite component in the seizure network following seizure repetition in an inherited form of generalized clonic seizures

Perirhinal cortex (PRh) is strongly implicated in neuronal networks subserving forebrain-driven partial onset seizures, but whether PRh plays a role in generalized onset seizures is unclear. The moderate seizure severity substrain of genetically epilepsy-prone rats (GEPR-3s) exhibits generalized onset clonic audiogenic seizures (AGS), but following repetitive AGS (AGS kindling), an additional behavior, facial and forelimb (F&F) clonus emerges immediately following generalized clonus. F&F clonus is thought to be driven from forebrain structures. The present in vivo study used PRh focal blockade or extracellular PRh neuronal recording with simultaneous behavioral observations to examine the role played by PRh in AGS neuronal networks before and after AGS kindling in GEPR-3s. Bilateral microinjection of an NMDA receptor antagonist [2-amino-7-phosphonoheptanoic acid, AP7 (0.2-7.5 nmol/side)] into PRh did not affect generalized clonus before or after AGS kindling. However, complete and reversible blockade of only the F&F clonic seizure behavior was induced by AP7 (1 and 7.5 nmol) in AGS-kindled GEPR-3s. Significant increases in PRh neuronal responses to acoustic stimuli occurred after AGS kindling. Tonic PRh neuronal firing patterns appeared during generalized clonus before and after AGS kindling. During F&F clonus, burst firing, an indicator of increased excitability, appeared in PRh neurons. These neurophysiological and microinjection findings support a critical role of PRh in generation of this AGS kindling-induced convulsive behavior. These data are the first indication that PRh participates importantly in the neuronal network for AGS as a result of AGS kindling and demonstrate a previously unknown involvement of PRh in generalized onset seizures.