The relationship between expressive suppression, therapeutic bond, and treatment outcomes of a positive affect intervention for adults with anxiety and/or depression

Expressive suppression (ES; reducing emotional expression) is linked with reduced social connectedness in individuals with anxiety or depression. One implication is that people who use ES may have difficulty establishing a bond with their therapist which may impede clinical improvement. We examined this hypothesis in 33 adults with clinically elevated anxiety or depression receiving treatment focused on enhancing positive thoughts, emotions, and behaviors. At baseline, participants rated ES for positive and negative emotions during a standardized conversation task designed to generate connectedness. They also rated measures of early (session 3) perceived therapeutic bond and treatment outcomes (i.e. positive affect and social connectedness). ES of positive (r = -.39, p = .018), but not negative (r = .06, p = .747), emotions was negatively associated with therapeutic bond. Therapeutic bond mediated the relationship between greater ES of positive emotions during affiliation and lower post-treatment positive affect, 95% bias-corrected bootstrap confidence interval [-0.021, -0.000], adjusted for pre-treatment positive affect, as well as lower post-treatment social connectedness [-0.397, -0.015]; however, the indirect effect was not significant when accounting for pre-treatment social connectedness (p > .05). ES of positive emotions may be an important factor in the development of therapeutic bond and therefore treatment outcomes for individuals with anxiety or depression.

Positive and negative affect change following psychotherapeutic treatment for anxiety-related disorders: A systematic review and meta-analysis

BACKGROUND

Anxiety-related disorders feature elevated negative affect (NA), and in some cases, diminished positive affect (PA). It remains unclear how well extant psychotherapies for anxiety-related disorders improve PA versus NA.

METHODS

We systematically searched the Cochrane Central Register of Controlled Trials, PubMed, PsychInfo, and Web of Science databases. Records included studies involving (1) patients with a principal or co-principal diagnosis of at least one anxiety-related disorder (i.e., generalized anxiety, social anxiety, panic, agoraphobia, health anxiety, specific phobia, obsessive-compulsive disorder, or posttraumatic stress disorder), and (2) pre- and post-treatment PA and NA scores or a change index between pre- and post-treatment PA and NA scores. Effect sizes were calculated for meta-analyses.

RESULTS

Fourteen studies with 1001 adults with an anxiety-related disorder were included. Psychotherapeutic interventions included cognitive behavioral, present-centered, and imagery-based approaches. Treatments reduced NA (g = -0.90; 95%CI [-1.19, -0.61]) to a greater extent than they improved PA (g = 0.27; 95%CI [0.05, 0.59]), Z = -5.26, p < .001. The limited number of studies available precluded analyses of the relationship between changes in affect and symptoms.

LIMITATIONS

Results should be considered with caution given the small number and heterogeneity of included studies.

CONCLUSIONS

Current psychotherapeutic interventions for anxiety-related disorders may not improve PA and NA to comparable levels.

Childhood Trauma Predicts Positive Expressive Suppression During Social Affiliation in Adults With Anxiety and/or Depression: Implications for Social Functioning

Experiencing childhood trauma (CT) can create barriers for developing relationships and is a risk factor for anxiety and depression. Expressive suppression (ES; i.e., reducing expression associated with experiencing emotions) might explain the link between CT and relationship formation difficulties. We examined the association between (1) CT and ES during a dyadic paradigm intended to facilitate connectedness between unacquainted partners and (2) ES and desire for future interaction (DFI). Individuals with an anxiety or depressive disorder diagnosis (N = 77) interacted with a trained confederate; partners answered a series of increasingly intimate questions about themselves. Participant ES for positive and negative emotions, and participant and confederate DFI were collected during the task. Participants completed global anxiety, depression, and CT measures. CT correlated with positive (r = .35, p = .002), but not negative, ES (r = .13, p = .273). In a multiple linear regression model, CT predicted positive ES beyond symptom variables and gender, β = .318, t = 2.59, p = .012. Positive ES correlated with participant (r = -.38, p = .001) and confederate DFI (r = -.40, p<.01); and predicted participant DFI beyond symptom variables and ethnicity, β = -.358, t = -3.18, p = .002, and confederate DFI, β = -.390, t = -3.51, p = .001, beyond symptom variables. Mediation analyses suggested positive ES accounted for the relationship between greater CT severity and less desire for future interaction from participants, 95%CI [-0.26, -0.02], and confederates, [-0.38, -0.01]. Positive ES may be an important factor in the reduced capacity to form new social relationships for individuals with a history of CT, anxiety, and depression.

Baseline executive functioning moderates treatment-related changes in quality of life in veterans with posttraumatic stress disorder and comorbid traumatic brain injury

Posttraumatic stress disorder (PTSD) treatment has been associated with improvement in quality of life (QOL); however, little is known about factors that moderate treatment-related changes in QOL, particularly cognitive factors. Executive functioning (EF) is important for success across all aspects of everyday life and predicts better psychological and physical health. EF is important to QOL, but more work is needed to better understand the association between EF and QOL improvements following interventions. We hypothesized that poorer baseline EF would be associated with less improvement in overall life satisfaction and satisfaction with health following PTSD treatment. U.S. veterans who served after the September 11, 2001 terrorist attacks (post 9-11; N = 80) with PTSD and a history of mild-to-moderate traumatic brain injury were randomized to standard cognitive processing therapy (CPT) or CPT combined with cognitive rehabilitation (SMART-CPT). Multilevel modeling was used to examine whether baseline EF performance was associated with changes in QOL scores from pretreatment to follow-up across both groups. Results indicated that poorer baseline performance on EF tests of working memory and inhibition were associated with less treatment-related improvements in general life satisfaction and satisfaction with health, rs = .26-.36. Treatment condition did not moderate any results. Future research should examine whether implementing EF-focused techniques before and/or concurrently with CPT for individuals with poorer baseline working memory and inhibition enhances QOL treatment gains, particularly in terms of general life and health-related satisfaction.

Examining affective reactivity as a link between suicidality and social disconnection

The link between suicidality and social disconnection is well-established. We explored possible mechanisms that may account for this link using a positive and negative valence systems framework in a clinical sample with and without suicidality (i.e., suicidal ideation and/or behaviors in the past month). Participants (N = 228) interacted with a trained confederate during a controlled conversation task designed to generate social affiliation. Participant-rated positive affect (PA) and negative affect (NA) were collected during the task (baseline, anticipation, post). Participant-rated desire for future interaction was collected after the task. We tested if (1) groups with (n = 82) and without (n = 146) suicidality differed in affect during the task and (2) whether affect accounted for the link between suicidality and desire for future interaction. Results revealed that groups differed in PA, but not NA, throughout the task. Participants with suicidality reported no significant changes in PA over the task (ps > .05); and, experienced less PA at post-task compared to those without (p = .003, d = 0.38) whereas participants without suicidality reported increased PA at post-task compared to baseline and anticipation of the task, ps < .001. Mediation analysis suggested blunted post-task PA accounted for the relationship between suicidality and less desire for future interaction, 95%CI [-2.59,-0.51]. Diminished PA reactivity during social affiliation opportunities may help explain the link between suicidality and social disconnection. Preliminary findings highlight PA as a potential mechanistic target for improving social connection for individuals at risk for suicide, though prospective and experimental research is needed.

Mechanisms through which executive dysfunction influences suicidal ideation in combat-exposed Iraq and Afghanistan veterans

OBJECTIVE

Executive dysfunction has previously been associated with suicidality, but it remains unclear how deficits in executive functioning contribute to increased suicidal thoughts and behaviors. Although it has been proposed that poorer executive functioning leads to difficulty generating and implementing appropriate coping strategies to regulate distress and inhibit suicidal thoughts and behaviors, studies have not systematically examined these relationships. Therefore, the present study examined various hypotheses to elucidate the mechanisms through which executive dysfunction influences suicidal ideation (SI) in combat-exposed Iraq/Afghanistan veterans.

METHOD

Veterans who endorsed SI were compared to those who denied SI on demographic and diagnostic variables and measures of neuropsychological functioning, psychological symptoms, coping styles, and combat experiences. Serial mediation models were tested to examine mechanistic relationships among executive functioning, psychological distress, coping, and SI.

RESULTS

Those who endorsed SI had worse executive functioning, greater psychological distress, and greater avoidant coping relative to those who denied SI. Serial mediation model testing indicated a significant indirect path, such that executive dysfunction increased psychological distress, which in turn increased avoidant coping, leading to SI.

CONCLUSIONS

Findings support and extend previous hypotheses regarding how executive functioning contributes to increased risk of suicidality via increased distress and avoidant coping. Intervention efforts focused on reducing suicidality may benefit from techniques that enhance executive functioning (e.g. computerized training, cognitive rehabilitation) and in turn reduce distress prior to targeting coping strategies.

Anhedonia in Anxiety Disorders

Humans, like other animals, are fundamentally motivated to pursue rewarding outcomes and avoid aversive ones. Anxiety disorders are conceptualized, defined, and treated based on heightened sensitivity to perceived aversive outcomes, including imminent threats as well as those that are uncertain yet could occur in the future. Avoidance is the central strategy used to mitigate anticipated aversive outcomes - often at the cost of sacrificing potential rewards and hindering people from obtaining desired outcomes. It is for these reasons that people are often motivated to seek treatment. In this chapter, we consider whether and how anhedonia - the loss of interest in pursuing and/or reduced responsiveness to rewarding outcomes - may serve as a barrier to recovering from clinically impairing anxiety. Increasingly recognized as a prominent symptom in many individuals with elevated anxiety, anhedonia is not explicitly considered within prevailing theoretical models or treatment approaches of anxiety. Our goal, therefore, is to review what is known about anhedonia within the anxiety disorders and then integrate this knowledge into a functional perspective to consider how anhedonia could maintain anxiety and limit treatment response. Our overarching thesis is that anhedonia disrupts the key processes that are central to supporting anxiety recovery. We end this chapter by considering how explicitly targeting anhedonia in treatment can optimize outcomes for anxiety disorders.

Association between neurocognitive functioning and suicide attempts in U.S. Army Soldiers

BACKGROUND

Suicide is a serious public health problem, including among U.S. Army personnel. There is great interest in discovering objective predictors of suicide and non-fatal suicidal behaviors. The current study examined the association between neurocognitive functioning and pre-military history of suicide attempts (SA) and post-enlistment onset of SA.

METHODS

New Soldiers reporting for Basic Combat Training (N = 38,507) completed a comprehensive computerized neurocognitive assessment battery and self-report questionnaires. A subset of Soldiers (n = 6216) completed a follow-up survey, including assessment of lifetime SA, 3-7 years later.

RESULTS

Six hundred eighty-nine Soldiers indicated lifetime SA at baseline and 210 Soldiers indicated new-onset SA at follow-up. Regression analyses, adjusted for demographic variables, revealed significant bivariate associations between neurocognitive performance on measures of sustained attention, impulsivity, working memory, and emotion recognition and lifetime SA at baseline. In a multivariable model including each of these measures as predictors, poorer impulse control and quicker response times on an emotion recognition measure were significantly and independently associated with increased odds of lifetime SA. A second model predicted new-onset SA at follow-up for Soldiers who did not indicate a history of SA at baseline. Poorer impulse control on a measure of sustained attention was predictive of new-onset SA.

LIMITATIONS

Effect sizes are small and of unlikely clinical predictive utility.

CONCLUSIONS

We simultaneously examined multiple neurocognitive domains as predictors of SA in a large, representative sample of new Army Soldiers. Impulsivity most strongly predicted past and future SA over and beyond other implicated cognitive-emotional domains.

White matter integrity, suicidal ideation, and cognitive dysfunction in combat-exposed Iraq and Afghanistan Veterans

White matter alterations in frontolimbic circuits and poorer cognitive functioning have been observed in individuals endorsing suicidality across numerous psychiatric conditions. However, relationships between white matter integrity, cognition, and suicidality in Veterans are poorly understood, particularly for those at increased risk for suicide due to mental health conditions (e.g., posttraumatic stress disorder, depression) and traumatic brain injury history. We (1) examined white matter alterations in combat-exposed Iraq/Afghanistan Veterans with and without suicidal ideation (SI) and (2) investigated relationships between white matter integrity and neuropsychological functioning in regions that differed between SI groups. No group differences were found regarding psychiatric diagnoses. Participants with SI had lower fractional anisotropy (FA) in the posterior corona radiata, superior corona radiata, and superior longitudinal fasciculus relative to those without SI. Worse processing speed/attention performance was associated with lower FA in the superior longitudinal fasciculus, while worse executive functioning performance was associated with lower FA in the superior corona radiata and superior longitudinal fasciculus. Memory performance was not associated with FA. These findings suggest that white matter integrity may be involved in cognitive dysfunction and increased risk for SI. Interventions that target cognitive dysfunction may ameliorate SI, and in turn, reduce risk for suicide among Veterans.

Self-efficacy and coping style in Iraq and Afghanistan-era veterans with and without mild traumatic brain injury and posttraumatic stress disorder

OBJECTIVE

To examine self-efficacy and coping style in combat-exposed Veterans with and without mild traumatic brain injury (mTBI) history and posttraumatic stress disorder (PTSD).

METHODS

Veterans (N = 81) were categorized into four groups: comorbid mTBI and PTSD (n = 23), PTSD-only (n = 16), mTBI-only (n = 25), and combat-exposed controls (n = 17). Outcomes included the Self-Efficacy for Symptom Management Scale and the Brief Coping Orientation to Problems Experienced.

RESULTS

Significant group effects were found on self-efficacy and coping style, even when adjusting for total mTBIs and psychiatric comorbidities. Post-hoc analyses revealed that the comorbid and PTSD-only groups generally had lower self-efficacy than the mTBI-only and control groups and that the PTSD-only group used less action-focused coping than the mTBI-only and control groups.

CONCLUSION

Our results suggest that self-efficacy and coping style vary as a function of mTBI history and PTSD status and that it may be important to integrate these malleable factors into interventions for this population.

Decreased myelin content of the fornix predicts poorer memory performance beyond vascular risk, hippocampal volume, and fractional anisotropy in nondemented older adults

Alterations to cerebral white matter tracts have been associated with cognitive decline in aging and Alzheimer's disease (AD). In particular, the fornix has been implicated as especially vulnerable given that it represents the primary outflow tract of the hippocampus. Despite this, little work has focused on the fornix using a potential early marker of white matter degeneration-myelin water fraction (MWF; an in vivo marker of myelin content). Therefore, we sought to (1) clarify associations between MWF in the fornix and memory functioning, and (2) examine whether fornix MWF relates to memory performance above and beyond hippocampal volume and conventional imaging measures of white matter that may not be as specific to alterations in myelin content. Forty nondemented older adults (mean age = 72.9 years) underwent an MRI exam and neuropsychological assessment. Multicomponent driven equilibrium single pulse observation of T1 and T2 (mcDESPOT) was used to quantify fornix MWF and diffusion tensor imaging (DTI) was used to measure fornix fractional anisotropy (FA). Adjusting for age, sex, education, and vascular risk factors, linear regression models revealed that, lower fornix MWF was significantly associated with poorer memory functioning (β = 0.405, p = .007) across our sample of older adults. Notably, fornix MWF remained a significant predictor of memory functioning (β = 0.380, p = .015) even after adjusting for fornix DTI FA and hippocampal volume (in addition to the above covariates). Given the observed associations between myelin and memory in older adults without dementia, MWF may be a useful early marker of dementia risk.

Post-concussive symptom endorsement and symptom attribution following remote mild traumatic brain injury in combat-exposed Veterans: An exploratory study

The purpose of this study was to examine rates of and relationships between "post-concussive" symptom endorsement and symptom attribution in Veterans with a history of mild traumatic brain injury (mTBI). This cross-sectional, exploratory study included 48 combat-exposed Iraq/Afghanistan Veterans with remote history of mTBI. All Veterans completed clinical interviews and self-report questionnaires assessing sociodemographic factors, injury and combat-related variables, psychiatric distress, self-efficacy, and coping style. To assess symptom endorsement and symptom attribution, a modified version of the Neurobehavioral Symptom Inventory was administered. Results showed that the most commonly endorsed "post-concussive" symptoms were several non-specific symptoms, while the symptoms most frequently attributed to mTBI included forgetfulness, poor concentration, and headaches. Furthermore, although there were some overlapping correlates of both symptom endorsement and symptom attribution, unique variables were associated with each domain. Specifically, symptom endorsement was uniquely associated with measures of psychiatric distress, while symptom attribution was uniquely associated with having a history of loss of consciousness and a greater degree of combat exposure. Taken together, results suggest that endorsement of symptoms may be significantly impacted by the presence of mental health comorbidities, but that perceptions or beliefs as to why symptoms are occurring are related more to mTBI and combat-related characteristics. Findings offer potential avenues for therapeutic intervention, emphasize the importance of psychoeducation, and highlight the need to consider using alternate terminology for these symptoms that promotes recovery and minimizes misattribution of symptoms.

Factors associated with employment and work perception in combat-exposed veterans

PURPOSE/OBJECTIVE

The purpose of this study was 2-fold: (a) to evaluate whether perception of work ability is associated with employment status in a sample of combat-exposed veterans, and (b) to determine whether the same sets of variables that are associated with employment status are also associated with perception of work ability. Research Method/Design: In this cross-sectional study, veterans (N = 83) underwent a neuropsychological assessment and completed questionnaires assessing demographic characteristics, combat-related experiences, and psychiatric and neurobehavioral/health-related symptoms. Primary outcomes of interest were employment status (unemployed vs. employed) and veterans' perception of whether their ability to work has declined due to an ongoing condition (yes vs. no).

RESULTS

A chi-square analysis revealed a significant relationship between perception of work ability and employment status. Additionally, psychiatric and neurobehavioral/health-related symptoms were associated with employment status and perception of work ability, whereas demographic characteristics (i.e., service-connected disability rating) and combat-related experiences (i.e., mTBI history) were only associated with perception of work ability. Objective cognitive functioning was not associated with employment status or perception of work ability.

CONCLUSIONS/IMPLICATIONS

Although preliminary, results suggest that perception of work ability is an important factor to consider when evaluating employment-related outcomes in veterans. Moreover, results indicate that while there is some overlap among the variables associated with employment status and perception of work ability, additional variables are linked with perception of work ability. Taken together, these findings suggest that perception of one's ability to work and factors that influence it may be particularly important treatment targets in the veteran population. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Associations Between Multiple Remote Mild TBIs and Objective Neuropsychological Functioning and Subjective Symptoms in Combat-Exposed Veterans

OBJECTIVE

The purpose of this study was to evaluate relationships between multiple mild traumatic brain injuries (mTBIs) and objective and subjective clinical outcomes in a sample of combat-exposed Veterans, adjusting for psychiatric distress and combat exposure.

METHOD

In this cross-sectional study, 73 combat-exposed Iraq/Afghanistan Veterans were divided into three groups based on mTBI history: 0 mTBIs (n = 31), 1-2 mTBIs (n = 21), and 3+ mTBIs (n = 21). Veterans with mTBI were assessed, on average, 7.78 years following their most recent mTBI. Participants underwent neuropsychological testing and completed self-report measures assessing neurobehavioral, sleep, and pain symptoms.

RESULTS

MANCOVAs adjusting for psychiatric distress and combat exposure showed no group differences on objective measures of attention/working memory, executive functioning, memory, and processing speed (all p's > .05; ηp2 = .00-.06). In contrast, there were significant group differences on neurobehavioral symptoms (p's = < .001-.036; ηp2 = .09-.43), sleep difficulties (p = .037; ηp2 = .09), and pain symptoms (p < .001; ηp2 = .21). Pairwise comparisons generally showed that the 3+ mTBI group self-reported the most severe symptoms, followed by comparable symptom reporting between the 0 and 1-2 mTBI groups.

CONCLUSIONS

History of multiple, remote mTBIs is associated with elevated subjective symptoms but not objective neuropsychological functioning in combat-exposed Veterans. These results advance understanding of the long-term consequences of repetitive mTBI in this population and suggest that Veterans with 3+ mTBIs may especially benefit from tailored treatments aimed at ameliorating specific neurobehavioral, sleep, and pain symptoms.

Mild traumatic brain injury characteristics do not negatively influence cognitive processing therapy attendance or outcomes

Some providers have expressed hesitation about the appropriateness of PTSD treatment for veterans with a history of mild traumatic brain injury (mTBI), given concerns that TBI-related sequelae may negatively affect PTSD treatment and/or should be the focus of treatment instead. However, research suggests that those with a history of mTBI can benefit from evidence-based PTSD treatment. To extend these findings, we examined whether specific mTBI injury markers were associated with PTSD treatment attendance and response. Iraq/Afghanistan-era veterans with PTSD and history of mTBI (N = 88) all received Cognitive Processing Therapy (CPT; either standard CPT without the trauma account or SMART-CPT, a modified version of CPT that included cognitive rehabilitation strategies). Analyses examined whether time since injury, presence of loss of consciousness (LOC) or posttraumatic amnesia (PTA), and number and mechanism of mTBIs were associated with treatment attendance or response. None of the five injury variables examined were associated with number of treatment sessions attended. Multilevel modeling indicated that injury variables did not moderate treatment response (across treatment conditions) in terms of change in PTSD and depression symptoms. There was a three-way interaction showing that individuals who denied ever experiencing LOC exhibited a greater decrease in PTSD and depression symptoms in standard CPT relative to those in the SMART-CPT. Thus, a history of mTBI should not preclude individuals from receiving standard CPT, regardless of injury characteristics. In fact, PTSD treatment should often be a first line of treatment for these veterans, given evidence of a mental health etiology to persistent post-concussive symptoms.

The Minnesota Multiphasic Personality Inventory-2-RF in Treatment-Seeking Veterans with History of Mild Traumatic Brain Injury

OBJECTIVE

This study examined the Minnesota Multiphasic Personality Inventory-Second Edition-Restructured Form (MMPI-2-RF) to better understand symptom presentation in a sample of treatment-seeking Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) Veterans with self-reported history of mild traumatic brain injury (mTBI).

METHOD

Participants underwent a comprehensive clinical neuropsychological battery including performance and symptom validity measures and self-report measures of depressive, posttraumatic, and post-concussive symptomatology. Those with possible symptom exaggeration (SE+) on the MMPI-2-RF were compared with those without (SE-) with regard to injury, psychiatric, validity, and cognitive variables.

RESULTS

Between 50% and 87% of participants demonstrated possible symptom exaggeration on one or more MMPI-2-RF validity scales, and a large majority were elevated on content scales related to cognitive, somatic, and emotional complaints. The SE+ group reported higher depressive, posttraumatic, and post-concussive symptomatology, had higher scores on symptom validity measures, and performed more poorly on neuropsychological measures compared with the SE- group. There were no group differences with regard to injury variables or performance validity measures. Participants were more likely to exhibit possible symptom exaggeration on cognitive/somatic compared with traditional psychopathological validity scales.

CONCLUSIONS

A sizable portion of treatment-seeking OEF/OIF Veterans demonstrated possible symptom exaggeration on MMPI-2-RF validity scales, which was associated with elevated scores on self-report measures and poorer cognitive performance, but not higher rates of performance validity failure, suggesting symptom and performance validity are distinct concepts. These findings have implications for the interpretation of clinical data in the context of possible symptom exaggeration and treatment in Veterans with persistent post-concussive symptoms.

Epileptogenesis in immature neocortical slices induced by 4-aminopyridine

The laminar site of onset of 4-aminopyridine (4AP)-induced epileptiform discharges in immature neocortical brain slices was localized to layer V using conventional extracellular field electrodes, current source-density analysis (CSD), and subdivided slices. Intracellular patch-electrode recordings in immature layer V neurons confirmed that intrinsically bursting (IB) neurons were not present at the ages studied or with bath application of 50-200 microM 4AP. IB properties were not being masked in the younger animals by the patch electrodes because typical IB neurons in layer V were seen in older rats when the same intracellular techniques were used. These results demonstrate that epileptiform activity can be initiated in the absence of IB neurons, and suggest that other factors are responsible for the preferential onset in layer V.

Chronic neocortical epileptogenesis in vitro

1. We used an in vitro model to explore critical aspects of chronic epileptogenesis. Partial neocortical isolations having intact blood supply were made in rat and guinea pig from postnatal day 7 to 34 and then examined 1 to 150 days later in standard brain slice preparations. 2. The epileptogenic potential of several different types of lesions was assessed. Slices containing transcortical (i.e., gray matter) lesions, with or without a contiguous white matter injury (i.e., "undercut"), developed chronic epileptogenesis after a latency of approximately 1-2 wk, manifested by evoked and spontaneous "interictal" discharges and evoked "ictal" events. The region of hyperexcitability did not extend beyond approximately 2 mm from the chronic transcortical lesion and was rarely observed in slices having only an apparent white matter injury. 3. Multiple recordings and current source density (CSD) analysis identified layer V as the source of the interictal discharge. 4. Significant differences in CSD profiles of the evoked interictal discharge occurred between chronically epileptogenic slices and control (noninjured) slices bathed in the convulsant, bicuculline methiodide, suggesting that mechanisms other than disinhibition must be involved in posttraumatic epileptogenesis. 5. Interictal events were blocked in most but not all chronically injured slices by application of the N-methyl-D-aspartate (NMDA) receptor antagonist D-2-amino-5-phosphonovalerate (D-AP5), suggesting that non-NMDA receptors were predominantly involved in some preparations. 6. This model of chronic epileptogenesis in vitro will be useful in studies relevant to mechanisms of posttraumatic epilepsy in man.