Epilepsy, schizophrenia, and the extended amygdala

Dissociation, Epileptiform Discharges and Chaos in the Brain: Toward a Neuroscientific Theory of Dissociation

Dissociated states represent pathological conditions when psychological trauma may emerge in a variety of forms such as psychic dissociative symptoms or, on the contrary, as paroxysms or other somatoform symptoms. There is evidence that epileptic activity plays an important role in the generation of dissociative states and it is able to generate various psychopathological processes as well as a wide spectrum of somatic symptoms or seizures. For the explanation of these connections between dissociative states and epileptic discharges the author proposes a neuroscientific model of dissociation based on the theory of competitive neural assemblies which can lead to chaotic self-organization in brain neural networks. This model is suggested as an integrative view interconnecting the various psychopathological and somatoform manifestations of dissociative states and suggests further possibilities for future research regarding common pathogenic mechanisms among epilepsy and mental disorders.

Increased Prevalence of Intermittent Rhythmic Delta or Theta Activity (IRDA/IRTA) in the Electroencephalograms (EEGs) of Patients with Borderline Personality Disorder

INTRODUCTION

An increased prevalence of pathological electroencephalography (EEG) signals has been reported in patients with borderline personality disorder (BPD). In an elaborative case description of such a patient with intermittent rhythmic delta and theta activity (IRDA/IRTA), the BPD symptoms where linked to the frequency of the IRDAs/IRTAs and vanished with the IRDAs/IRTAs following anticonvulsive therapy. This observation raised a question regarding the prevalence of such EEG abnormalities in BPD patients. The aim of this retrospective study was to identify the frequency of EEG abnormalities in a carefully analyzed psychiatric collective. Following earlier reports, we hypothesized an increased prevalence of EEG abnormalities in BPD patients.

PARTICIPANTS AND METHODS

We recruited 96 consecutive patients with BPD from the archive of a university clinic for psychiatry and psychotherapy, and compared the prevalence of EEG abnormalities to those of 76 healthy controls subjects. The EEGs were rated by three different blinded clinicians, including a consultant specializing in epilepsy from the local epilepsy center.

RESULTS

We found a significant increase in the prevalence of IRDAs and IRTAs in BPD patients (14.6%) compared to the control subjects (3.9%; p = 0.020).

DISCUSSION

In this blinded retrospective case-control study, we were able to confirm an increased prevalence of pathological EEG findings (IRDAs/IRTAs only) in BPD patients. The major limitation of this study is that the control group was not matched on age and gender. Therefore, the results should be regarded as preliminary findings of an open uncontrolled, retrospective study. Future research performing prospective, controlled studies is needed to verify our findings and answer the question of whether such EEG findings might predict a positive response to anticonvulsive pharmacological treatment.

Ontogenetic influence on rat susceptibility to lindane seizure after pretreatment with phencyclidine

The aim of the study was to determine the effects of early postnatal PCP treatment on the sensitivity of pubertal and adult rats to lindane proepileptogenic effects. Rat pups were treated with NaCl (0.9%) or PCP (10 mg/kg) at postnatal days 2, 6, 9 and 12. One control (NaCl-35) and one experimental (PCP-35) group have received lindane (4 mg/kg) at postnatal day 35, while others received lindane at postnatal day 65 (NaCl-65 and PCP-65). One week prior to lindane treatment three gold-plated EEG electrodes were implanted. Pubertal rats had significantly shorter latency time. After lindane, a prompt increase in power spectral density seen in PCP-treated groups vs. control was evident earlier in PCP-65 rats. The theta waves were significantly increased in PCP-35 and alpha rhythm in PCP-65 rats, when compared with corresponding controls. Postnatal PCP treatment increases the synchronization of brain electrical activity, thus contributing to the increased susceptibility to lindane.

Local area network inhibition: a model of a potentially important paraepileptic pathomechanism in neuropsychiatric disorders

Electroencephalographic abnormalities in the absence of any other major laboratory or imaging findings are a frequently encountered phenomenon in many psychiatric disorders. In some cases, clear-cut interictal epileptiform EEG abnormalities in patients with classic primary psychiatric disorders lead to referrals to epilepsy departments for diagnostic evaluation. Although video/EEG telemetry in these cases generally proves that there is no direct temporal link between the EEG pathologies and psychiatric symptoms, and therefore the psychiatric syndrome cannot be regarded as epilepsy, the relevance of the EEG abnormalities remains open to discussion. In this article we put forward the model of a paraepileptic pathomechanism, which might explain the pathogenetic role of such EEG pathologies, at least in subgroups of such patients. We propose that ictal or nonictal epileptic neurophysiological activity can lead to local area neuronal network inhibition (LANI). In this model clinical symptoms are related not to the excitatory epileptiform abnormalities themselves, but to the extent, site, and dynamics of the resulting local neuronal network inhibition. The LANI hypothesis is capable of explaining the complex relationship between EEG abnormalities and clinical symptoms in different neuropsychiatric syndromes and can be verified and falsified in empirical research.

Sensitization, epileptic-like symptoms and local synchronization in patients with paranoid schizophrenia

Recent findings indicate that changes in synchronization of neural activities underlying sensitization and kindling could be more comprehensively understood using nonlinear methods. With this aim we have examined local synchronization using novel measure of coarse-grained information rate (CIR) in 8 EEG signals recorded at different cortical areas in 44 patients with paranoid schizophrenia. The values of local synchronization that could reflect sensitization related changes in EEG activities of cortical sites were then related to psychometric measures of epileptic-like symptoms and positive and negative schizophrenia symptoms (PANSS). While no significant correlations between CIR and positive and negative symptoms have been found, statistically significant relationships described by Spearman correlation coefficients between CIR indices and results of LSCL-33 have been observed in 7 (of 8) EEG channels (r in the range from 0.307 to 0.374, p<0.05). Results of this study provide first supportive evidence for the relationship between local synchronization measured by CIR and epileptic-like symptoms in schizophrenia.

Lennart Heimer: concepts of the ventral striatum and extended amygdala

Dr. Lennart Heimer, the famous neuroanatomist of Swedish descent, died last year but left a legacy that will impact the neurosciences and potentially psychosurgery for years to come. He developed an anatomical technique for demonstrating the terminal boutons that helped to delineate basal forebrain anatomy. During these studies, he realized the relationship of basal forebrain structures to the limbic system, thus initiating the concept of the ventral striatum and parallel basal ganglia circuitry.

Heimer excelled as a teacher as well and honed his brain dissection technique to one of the most effective tools for understanding neuroanatomy. His legendary sessions with neurosurgical residents resulted in his recognition as one of the world’s leading fiber tract dissectors. His gentle, engaging manner has been documented in several media formats.

Dissociation and Neurobiological Consequences of Traumatic Stress

According to recent evidence traumatic stress is an important etiological factor in pathogenesis of psychiatric diseases. Typical psychological manifestation of the traumatic stress represents dissociative states. Dissociated states present pathological conditions where psychological trauma may emerge in a variety of forms such as psychic dissociative symptoms or on the other hand as somatoform symptoms including seizures. At this time there is evidence that temporal lobe seizure activity may produce dissociative syndrome and this activity likely may exist independently of neurological focal lesion. This conceptualization of dissociative phenomena is in accordance with findings that originate from the study of the relationship between epilepsy and mental illness and known as antagonism between epilepsy and psychosis or the so-called forced normalization. From this point of view the relationship between dissociation, epileptic activity and kindling phenomena represent useful concepts for understanding of neurobiological consequences of the traumatic stress and dissociation with respect to pathogenesis of stress-related mental diseases.

Activation of GABA(B) receptors reverses spontaneous gating deficits in juvenile DBA/2J mice

RATIONALE

Gamma-amino-butyric acid (GABA)(B) receptors play a key role in the pathophysiology of psychotic disorders. We previously reported that baclofen, the prototypical GABA(B) agonist, elicits antipsychotic-like effects in the rat paradigm of prepulse inhibition (PPI) of the startle, a highly validated animal model of schizophrenia.

OBJECTIVES

We studied the role of GABA(B) receptors in the spontaneous PPI deficits displayed by DBA/2J mice.

MATERIALS AND METHODS

We tested the effects of baclofen (1.25-5 mg/kg, intraperitoneal [i.p.]) in DBA/2J and C57BL/6J mice, in comparison to the antipsychotic drugs haloperidol (1 mg/kg, i.p.) and clozapine (5 mg/kg, i.p.). Furthermore, we investigated the expression of GABA(B) receptors in the brain of DBA/2J and C57BL/6J mice by quantitative autoradiography.

RESULTS

Baclofen dose-dependently restored PPI deficit in DBA/2J mice, in a fashion similar to the antipsychotic clozapine (5 mg/kg, i.p.). This effect was reversed by pretreatment with the GABA(B) antagonist SCH50211 (50 mg/kg, i.p.). In contrast, baclofen did not affect PPI in C57BL/6J mice. Finally, quantitative autoradiographic analyses assessed a lower GABA(B) receptor expression in DBA/2J mice in comparison to C57BL/6J controls in the prefrontal cortex and hippocampus but not in other brain regions.

CONCLUSIONS

Our data highlight GABA(B) receptors as an important substrate for sensorimotor gating control in DBA/2J mice and encourage further investigations on the role of GABA(B) receptors in sensorimotor gating, as well as in the pathophysiology of psychotic disturbances.

The price of seizure control: dynorphins in interictal and postictal psychosis

Postictal and interictal psychoses are relatively common complicating factors in the clinical course of epilepsy, yet their neurobiological substrates are poorly understood. Recent evidence shows that kappa opioid receptor (KOR) activation elicits anticonvulsant and psychotomimetic effects. In view of this background, here we introduce the hypothesis that epilepsy-related psychoses may partially result from excessive hippocampal dynorphin release and kappa opioid receptor overstimulation aimed at seizure control.

A rat model for neural circuitry abnormalities in schizophrenia

Animal models for complex brain disorders, such as schizophrenia, are essential for the interpretation of postmortem findings. These models allow empirical testing of hypotheses regarding the role of genetic and environmental factors, the pathophysiological mechanisms and brain circuits that are responsible for specific neural abnormalities and their associated behavioral impairment, and the effectiveness of therapeutic treatments relative to these diseases. Recently, we developed a rodent model for neural circuitry abnormalities in discrete corticolimbic subregions of subjects with major psychoses. According to our protocol, the GABA-A receptor antagonist picrotoxin is stereotaxically infused in the basolateral amygdala to mimic a GABA defect in this region that is postulated to occur in these disorders. This protocol has been tested with a number of acute and chronic time schedules. Following picrotoxin administration in the basolateral amygdala, changes in GABAergic neurons and/or terminals in hippocampal regions CA2/3 are observed, similar to those seen in major psychoses, as well as a marked reduction in GABA-receptor-mediated currents in pyramidal neurons of this region. This has established the construct and predictive validity of this model for studying limbic-lobe circuitry abnormalities. We propose that this modeling strategy may provide a valid alternative to isomorphic models of these diseases.

Role of stress, corticotrophin releasing factor (CRF) and amygdala plasticity in chronic anxiety

Stress initiates a series of neuronal responses that prepare an organism to adapt to new environmental challenges. However, chronic stress may lead to maladaptive responses that can result in psychiatric syndromes such as anxiety and depressive disorders. Corticotropin-releasing factor (CRF) has been identified as a key neuropeptide responsible for initiating many of the endocrine, autonomic and behavioral responses to stress. The amygdala expresses high concentrations of CRF receptors and is itself a major extrahypothalamic source of CRF containing neurons. Within the amygdala, the basolateral nucleus (BLA) has an important role in regulating anxiety and affective responses. During periods of stress, CRF is released into the amygdala and local CRF receptor activation has been postulated as a substrate for stress-induced alterations in affective behavior. Previous studies have suggested that synaptic plasticity in the BLA contributes to mechanisms underlying long-term changes in the regulation of affective behaviors. Several studies have shown that acute glutamate receptor-mediated activation, by either GABA-mediated disinhibition or CRF-mediated excitation, induces long-term synaptic plasticity and increases the excitability of BLA neurons. This review summarizes some of the data supporting the hypotheses that stress induced plasticity within the amygdala may be a critical step in the pathophysiology of the development of chronic anxiety states. It is further proposed that such a change in the limbic neural circuitry is involved in the transition from normal vigilance responses to pathological anxiety, leading to syndromes such as panic and post-traumatic stress disorders.

Long-term effects of amygdala GABA receptor blockade on specific subpopulations of hippocampal interneurons

Growing evidence indicates that the amygdala modulates hippocampal functions. To test the hypothesis that this modulation may involve long-lasting effects on interneuronal networks in the hippocampus, changes in the expression of neurochemical markers specific for different interneuronal subpopulations were assessed in adult rats 96 h following acute infusion of low doses of the GABAA receptor antagonist picrotoxin into the amygdala. The numerical density (Nd) of somata showing immunoreactivity (IR) for parvalbumin (PVB) was decreased in dentate gyrus (DG) and the CA4-2 region, while that of calretinin (CR)-IR was decreased in DG and CA2. The Nd of calbindin D28k (CB)-IR somata was decreased in CA3-2. The densities of axon terminals arising from PVB-IR and cholecystokinin (CCK)-IR basket neurons were also altered, with those of CCK-IR terminals increased across all sectors, while PVB-IR terminals were decreased only in the CA region. Increases in CCK-IR terminals were paralleled by increases of terminals with IR for the 65-kD isoform of glutamate decarboxylase (GAD65). Mixed-effects statistical models, adapted specifically for these analyses, indicated that perturbations of amygdalar inputs to the hippocampus significantly alter the drive that hippocampal PVB-, CR-, and CB-IR neurons within the dentate gyrus/CA4 region exercise on CCK-IR terminals within the same region as well as in CA3-1. These results suggest that amygdalar modulation of specific neuronal subpopulations may induce lasting and far-reaching changes in the hippocampus during normal functioning, as well as in diseases involving a disruption of amygdalar activity. In particular, changes in specific interneuronal markers within selective hippocampal sectors detected in the present results are strikingly similar to those reported in this region in schizophrenia. These similarities suggest that, in this disease, a disruption of GABAergic transmission within the amygdala may play a significant role in the induction of abnormalities in the hippocampus.

Real-time neural activity and connectivity in healthy individuals and schizophrenia patients

Processing of facial information is distributed across several brain regions, as has been shown recently in many neuroimaging studies. Disturbances in accurate face processing have been repeatedly demonstrated in different stages of schizophrenia. Recently, electroencephalography (EEG) and tomographic analysis of average magnetoencephalographic (MEG) data were used to define the latencies of significant regional brain activations in healthy and schizophrenic subjects elicited during the recognition of facial expression of emotions. The current study re-examines these results using tomographic analysis of single trial MEG data. In addition to the areas identified by the analysis of the average MEG data, statistically significant activity is identified in several other areas, including a sustained increase in the right amygdala activity in response to emotional faces in schizophrenic subjects. The single trial analysis demonstrated that the reduced activations identified from the average MEG signal of schizophrenic subjects is due to high variability across single trials rather than reduced activity in each single trial. In control subjects, direct measures of linkage demonstrate distinct stages of processing of emotional faces within well-defined network of brain regions. Activity in each node of the network, confined to 30 to 40 ms latency windows, is linked to earlier and later activations of the other nodes of the network. In schizophrenic subjects, no such well-defined stages of processing were observed. Instead, the activations, although strong were poorly linked to each other, managing only isolated links between pairs of areas.

Treatment of interictal psychiatric disorder in epilepsy. II. Chronic psychosis

BACKGROUND

Interictal psychosis is a serious comorbid condition in epilepsy patients that would benefit from treatment with psychotropic medication.

OBJECTIVE

This paper gives an overview of the pathophysiology, symptomatology and treatment of the schizophrenia-like psychosis of epilepsy. Use of the term 'interictal chronic psychosis' is suggested, to conform to current DSM-IV classification of schizophrenia.

METHODS

Literature review supplemented by clinical experience. There is a lack of randomized control trials (RCTs) concerning effectiveness and side-effects of neuroleptics in epilepsy patients.

RESULTS

Hypotheses concerning the pathophysiology of the interictal chronic psychosis are discussed. The concept of forced normalization and alternative psychosis is based on case descriptions, and was not substantiated by systematic research. The kindling hypothesis seems promising, but was never confirmed in humans. A third theory, supported by some studies, suggests that inhibitory cerebral mechanisms enhance psychotic symptoms in epilepsy patients. Treatment strategies are based on case studies and open studies by lack of RCTs. Treatment should consider the optimalization of the dosage of antiepileptics in combination with one or two antidepressants, mood stabilizers and/or atypical neuroleptics. Surgery plays no significant role in the treatment of treatment-refractive epilepsy with interictal chronic psychotic symptoms.

CONCLUSION

There is a prominent role of antidepressant or double antidepressant treatment strategies in patients with epilepsy and interictal chronic psychosis compared with treatment guidelines of chronic psychotic patients in general psychiatry.

Amygdala pathology in psychosis of epilepsy: A magnetic resonance imaging study in patients with temporal lobe epilepsy

Psychosis of epilepsy (POE) has been recognized as a severe complication of chronic intractable epilepsy for more than a century. Most of the clinical symptoms of POE are reminiscent of schizophrenia. Nevertheless, there is general agreement that the phenomenology of POE differs from classical schizophrenia. The temporal lobe hypothesis of schizophrenia put forward in the 1960s notes that episodes with paranoid psychoses are more prevalent in temporal lobe epilepsy (TLE). However, the aetiology and pathogenesis of POE are poorly understood. One of the strongest biological findings in schizophrenia is volume loss of temporal lobe structures and the hippocampus in particular. In order to test the hypothesis that atrophy of the hippocampus and the amygdala is found in patients with TLE and POE, we performed a retrospective study of all patients with TLE who were admitted to the assessment unit of the Chalfont Centre for Epilepsy from 1995 until 1999. Twenty-six (2.6%) of these 1008 patients fulfilled inclusion criteria and were compared with 24 patients with TLE without psychopathology and 20 healthy volunteers. All patients underwent extensive MRI investigations, including volumetric data sets and quantitative T(2 )relaxometry. We found that patients with TLE and POE differed from patients with TLE alone and healthy volunteers in that the total brain volumes were significantly smaller. While there were no differences in hippocampal volumes between the three study groups, there was a significant 16-18% enlargement of the amygdala on both sides in patients with POE. Our findings support the notion that POE is a distinct nosologic entity differing from schizophrenia not only in clinical details but also in neurobiological aspects. The finding of amygdala enlargement agrees with the observation of an association between dysphoric disorders of epilepsy and POE described nearly 100 years ago.

P300 asymmetry in schizophrenia: a meta-analysis

P300 event-related brain potential (ERP) amplitude is smaller in patients with schizophrenia compared to unaffected controls, but whether left temporal component amplitude is also smaller is debated. The present study employed meta-analytical methods to quantitatively assess previous P300 schizophrenia asymmetry findings. All P300 articles on schizophrenia using an auditory oddball paradigm published before January 2000 were obtained by comprehensive literature searches and cross-referencing for related articles. A total of 19 original articles reporting complete midline electrode data and 11 articles reporting lateral asymmetry electrode data were reviewed, which included different independent conditions that yielded 50 independent data sets. P300 amplitude differences between patients with schizophrenia and control subjects from the midline electrodes yielded effect sizes that differed among recording sites, such that Fz was significantly smaller than Pz, with Cz effect sizes smaller than Pz but larger than Fz. Comparison of P300 amplitude from the lateral data for the T3 and T4 electrodes found no reliable effect size difference when these electrodes were analyzed separately. However, comparison of P300 amplitude effect sizes from the TCP1 was significantly larger than that from the TCP2 when these electrodes were analyzed separately. P300 amplitude is smaller overall in patients with schizophrenia compared to control subjects and differs in its effect size topography across the midline and temporal electrode sites, with the strongest effect sizes obtained for the Pz midline and TCP1 lateral electrodes.

Amygdalar activation alters the hippocampal GABA system: "partial" modelling for postmortem changes in schizophrenia

Abnormalities in amygdala and hippocampus have been shown to coexist in schizophrenia (SZ). In the hippocampus, compelling evidence suggests that a disruption of GABA neurotransmission is present mainly in sectors CA4, CA3, and CA2. The amygdala sends important inputs to the hippocampus and is also believed to have a defective GABA system in schizophrenia. To explore the possibility that changes in the hippocampal GABAergic system could be related to an increased inflow of activity originating in the amygdala, a "partial" animal model has been developed. In awake, freely moving, rats a GABA(A) receptor antagonist was infused locally into the basolateral nuclear complex of the amygdala (BLn). Within 2 hours, a decreased density of both the 65- and 67-kDa isoforms of glutamate decarboxylase (GAD(65) and GAD(67)) -immunoreactive (IR) terminals was detected on neuron somata in sectors CA3 and CA2, but not in CA1, CA3, or dentate gyrus. An increase of GAD(67)-IR somata was also found in the dentate gyrus and CA4. In anterograde tracer studies, amygdalo-hippocampal projection fibers were exclusively found in CA3 and CA2, but not CA1. Taken together, these results indicate that activation of amygdalo-hippocampal afferents is associated with the induction of significant changes in the GABA system of the hippocampus, with a subregional distribution that is remarkably similar to that found in SZ. Under pathologic conditions, an excessive discharge of excitatory activity emanating from the amygdala could be capable of altering inhibitory modulation along the trisynaptic pathway. This mechanism may potentially contribute to disturbances of GABAergic function in the major psychoses. Such "partial" rodent modelling provides an important strategy for deciphering the effect of altered cortico-limbic circuits in SZ.

[Anesthesia for epilepsy surgery]

Epilepsy is rather common, affecting 0.5 to 2% of the population. Numerous patients, particularly those resistant to the antiepileptic therapy, can be surgically treated after a thorough evaluation. Surgery for epilepsy can be carried out either under general or local anaesthesia with sedation. This second approach is reserved for the extirpation of foci localised in motor, sensory or language areas. During the preoperative anaesthetic evaluation, two specific points have to be taken into account: the psychological aspect and the antiepileptic medication. During the procedure, an electrocorticography with or without stimulation may be indicated, particularly when a perioperative stimulation is scheduled. Low doses of volatile agents are chosen, and no curare and large doses of benzodiazepines and barbiturates. Awakening takes place on the operation table for a rapid and reliable neurological evaluation. During procedures performed under local anaesthesia, the anaesthetist must be ready at any time to intubate the patient in order to secure the airway.