Kim L. Felmingham

Trauma modulates amygdala and medial prefrontal responses to consciously attended fear.

Effective fear processing relies on the amygdala and medial prefrontal cortex (MPFC). Post-trauma reactions provide a compelling model for examining how the heightened experience of fear impacts these systems. Post-traumatic stress disorder (PTSD) has been associated with excessive amygdala and a lack of MPFC activity in response to nonconscious facial signals of fear, but responses to consciously processed facial fear stimuli have not been examined. We used functional MRI to elucidate the effect of trauma reactions on amygdala-MPFC function during an overt fear perception task. Subjects with PTSD (n = 13) and matched non-traumatized healthy subjects (n = 13) viewed 15 blocks of eight fearful face stimuli alternating pseudorandomly with 15 blocks of neutral faces (stimulus duration 500 ms; ISI 767 ms). We used random effects analyses in SPM2 to examine within- and between-group differences in the MPFC and amygdala search regions of interest. Time series data were used to examine amygdala-MPFC associations and changes across the first (Early) versus second (Late) phases of the experiment. Relative to non-traumatized subjects, PTSD subjects showed a marked bilateral reduction in MPFC activity (in particular, right anterior cingulate cortex, ACC), which showed a different Early-Late pattern to non-traumatized subjects and was more pronounced with greater trauma impact and symptomatology. PTSD subjects also showed a small but significant enhancement in left amygdala activity, most apparent during the Late phase, but reduction in Early right amygdala response. Over the time course, trauma was related to a distinct pattern of ACC and amygdala connections. The findings suggest that major life trauma may disrupt the normal pattern of medial prefrontal and amygdala regulation.

Amygdala and ventral anterior cingulate activation predicts treatment response to cognitive behaviour therapy for post-traumatic stress disorder

BACKGROUND Although cognitive behaviour therapy (CBT) is the treatment of choice for post-traumatic stress disorder (PTSD), approximately half of patients do not respond to CBT. No studies have investigated the capacity for neural responses during fear processing to predict treatment response in PTSD. METHOD Functional magnetic resonance imaging (fMRI) responses of the brain were examined in individuals with PTSD (n=14). fMRI was examined in response to fearful and neutral facial expressions presented rapidly in a backwards masking paradigm adapted for a 1.5 T scanner. Patients then received eight sessions of CBT that comprised education, imaginal and in vivo exposure, and cognitive therapy. Treatment response was assessed 6 months after therapy completion. RESULTS Seven patients were treatment responders (defined as a reduction of 50% of pretreatment scores) and seven were non-responders. Poor improvement after treatment was associated with greater bilateral amygdala and ventral anterior cingulate activation in response to masked fearful faces. CONCLUSIONS Excessive fear responses in response to fear-eliciting stimuli may be a key factor in limiting responses to CBT for PTSD. This excessive amygdala response to fear may reflect difficulty in managing anxiety reactions elicited during CBT, and this factor may limit optimal response to therapy.

Depression, Comorbid Anxiety Disorders, and Heart Rate Variability in Physically Healthy, Unmedicated Patients: Implications for Cardiovascular Risk

Context There is evidence that heart rate variability (HRV) is reduced in major depressive disorder (MDD), although there is debate about whether this effect is caused by medication or the disorder per se. MDD is associated with a two to fourfold increase in the risk of cardiac mortality, and HRV is a robust predictor of cardiac mortality; determining a direct link between HRV and not only MDD, but common comorbid anxiety disorders, will point to psychiatric indicators for cardiovascular risk reduction. Objective To determine in physically healthy, unmedicated patients whether (1) HRV is reduced in MDD relative to controls, and (2) HRV reductions are driven by MDD alone, comorbid generalized anxiety disorder (GAD, characterized by anxious anticipation), or comorbid panic and posttraumatic stress disorders (PD/PTSD, characterized by anxious arousal). Design, Setting, and Patients A case-control study in 2006 and 2007 on 73 MDD patients, including 24 without anxiety comorbidity, 24 with GAD, and 14 with PD/PTSD. Seventy-three MDD and 94 healthy age- and sex-matched control participants were recruited from the general community. Participants had no history of drug addiction, alcoholism, brain injury, loss of consciousness, stroke, neurological disorder, or serious medical conditions. There were no significant differences between the four groups in age, gender, BMI, or alcohol use. Main Outcome Measures HRV was calculated from electrocardiography under a standardized short-term resting state condition. Results HRV was reduced in MDD relative to controls, an effect associated with a medium effect size. MDD participants with comorbid generalized anxiety disorder displayed the greatest reductions in HRV relative to controls, an effect associated with a large effect size. Conclusions Unmedicated, physically healthy MDD patients with and without comorbid anxiety had reduced HRV. Those with comorbid GAD showed the greatest reductions. Implications for cardiovascular risk reduction strategies in otherwise healthy patients with psychiatric illness are discussed.

Enhanced amygdala and medial prefrontal activation during nonconscious processing of fear in posttraumatic stress disorder: An fMRI study

Biological models of posttraumatic stress disorder (PTSD) suggest that patients will display heightened amygdala but decreased medial prefrontal activity during processing of fear stimuli. However, a rapid and automatic alerting mechanism for responding to nonconscious signals of fear suggests that PTSD may display heightened rather than decreased MPFC under nonconscious processing of fear stimuli. This study used functional magnetic resonance imaging to examine blood oxygenation level‐dependent signal changes during nonconscious presentation (16.7 ms, masked) of fearful and neutral faces in 15 participants with PTSD and 15 age and sex‐matched healthy control participants. Results indicate that PTSD participants display increased amygdala and MPFC activity during nonconscious processing of fearful faces. These data extend existing models by suggesting that the impaired MPFC activation in PTSD may be limited to conscious fear processing. Hum Brain Mapp, 2008.

Changes in Anterior Cingulate and Amygdala After Cognitive Behavior Therapy of Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) may develop from impaired extinction of conditioned fear responses. Exposure-based treatment of PTSD is thought to facilitate extinction learning (Charney, 2004). Fear extinction is mediated by inhibitory control of the ventromedial prefrontal cortex (vmPFC) over amygdala-based fear processes (Phelps, Delgado, Nearing, & LeDoux, 2004; Quirk, Russo, Barron, & LeBron, 2000). Most neuroimaging studies of PTSD reveal reduced vmPFC activity (particularly in rostral anterior cingulate cortex, or rACC; Lanius et al., 2001; Shin et al., 2005), and some find increased amygdala activity during threat processing (Shin et al., 2005). In addition, increased amygdala activity during fear conditioning and reduced vmPFC activity during extinction have been reported in PTSD (Bremner et al., 2005). Although PTSD patients show increased orbitofrontal and medial prefrontal activity following treatment with serotonin reuptake inhibitors (SSRIs; Fernandez et al., 2001; Seedat et al., 2004), no studies have investigated neural networks before and after exposure-based treatment of PTSD. We report the first such study. We hypothesized that symptom reduction would be associated with increased rACC activity and reduced amygdala activity during fear processing.

Aggressive behavior following traumatic brain injury: how common is common?

ObjectiveTo assess the prevalence and predictors of aggressive behavior among traumatic brain injury (TBI) survivors at 6, 24, and 60 months postdischarge. DesignMixed cross-sectional and longitudinal data from a 5-year follow-up study of discharged TBI patients analyzed retrospectively. SettingA specialized Brain Injury Rehabilitation Service of a tertiary referral hospital. PatientsTwo hundred twenty-eight (228) patients with moderate to severe TBI. Main Outcome MeasuresThe Overt Aggression Scale; injury-related variables (in particular, Glasgow Coma and Outcome scales and posttraumatic amnesia duration); and a battery of postdischarge questionnaires (Beck Depression Inventory, Trauma Complaints List, General Health Questionnaire, etc). ResultsAt any given follow-up period, 25% of the participants were classified as aggressive. Aggression, where present, was consistently associated with depression, concurrent traumatic complaints, younger age at injury, and low satisfaction with life rather than with injury, demographic, or premorbid characteristics. Depression was the factor that was most significantly associated with aggressive behavior at all times postinjury, followed by a younger age at the time of injury. ConclusionsAggression is a common, fluctuating, and long-term problem following TBI. The underlying association between aggression and psychosocial variables lends support to the provision of ongoing outreach services and psychological and behavioral interventions for all affected TBI survivors.

Neural Networks of Information Processing in Posttraumatic Stress Disorder: A Functional Magnetic Resonance Imaging Study

BACKGROUND Neuroimaging studies report reduced medial prefrontal cortical (particularly anterior cingulate) but enhanced amygdala response to fear signals in posttraumatic Stress Disorder (PTSD). We investigated whether anterior cingulate-amygdala dysregulation in PTSD would generalize to salient, but nonthreat related signals. METHODS Individuals with PTSD (n = 14) and age and sex-matched nontraumatized controls (n = 14) completed an auditory oddball paradigm adapted to functional magnetic resonance imaging at a 1.5-T field strength. RESULTS Controls displayed bilateral activation in ventral anterior cingulate and amygdala networks, and PTSD subjects showed bilateral dorsal anterior cingulate and amygdala activation to targets relative to nontargets. Compared to controls, PTSD subjects showed enhanced responses to targets in the dorsal and rostral anterior cingulate, and left amygdala. Whole-brain analyses confirmed the expected pattern of distributed prefrontal-parietal responses to targets in the oddball task. Greater activity in posterior parietal somatosensory regions was observed in PTSD. CONCLUSIONS Our findings of enhanced anterior cingulate responses in PTSD contrast with reports of reduced activity for threat stimuli, suggesting that the latter may be specific to processing of threat-related content. Activation in rostral and dorsal anterior cingulate, left amygdala and posterior parietal networks in response to salient, nonthreatening stimuli may reflect generalized hypervigilance.

Effects of diffuse axonal injury on speed of information processing following severe traumatic brain injury

To test the hypothesis that slowed information processing in traumatic brain injury is related to diffuse axonal injury (DAI), the authors compared 10 patients with predominant DAI (diffuse group) and minimal DAI (mixed injury group) on the Symbol Digit Modalities Test, simple and choice reaction time, Trail Making Tests A and B, and the Stroop Neuropsychological Screening Test. The diffuse group was slower than the mixed injury and control groups on basic speed of processing tasks. This difference was not apparent on complex speeded tasks once basic speed of processing was controlled for. The diffuse groups slower speed of processing was not accounted for by differences in injury severity, age, or time postinjury. The diffuse group showed greater recovery over time.

Dysautonomia after traumatic brain injury: a forgotten syndrome?

OBJECTIVES To better establish the clinical features, natural history, clinical management, and rehabilitation implications of dysautonomia after traumatic brain injury, and to highlight difficulties with previous nomenclature. METHODS Retrospective file review on 35 patients with dysautonomia and 35 sex and Glasgow coma scale score matched controls. Groups were compared on injury details, CT findings, physiological indices, and evidence of infections over the first 28 days after injury, clinical progress, and rehabilitation outcome. RESULTS the dysautonomia group were significantly worse than the control group on all variables studied except duration of stay in intensive care, the rate of clinically significant infections found, and changes in functional independence measure (FIM) scores. CONCLUSIONS Dysautonomia is a distinct clinical syndrome, associated with severe diffuse axonal injury and preadmission hypoxia. It is associated with a poorer functional outcome; however, both the controls and patients with dysautonomia show a similar magnitude of improvement as measured by changes in FIM scores. It is argued that delayed recognition and treatment of dysautonomia results in a preventable increase in morbidity.

A Randomized Controlled Trial of Exposure Therapy and Cognitive Restructuring for Posttraumatic Stress Disorder

Previous studies have reported that adding cognitive restructuring (CR) to exposure therapy does not enhance treatment gains in posttraumatic stress disorder (PTSD). This study investigated the extent to which CR would augment treatment response when provided with exposure therapy. The authors randomly allocated 118 civilian trauma survivors with PTSD to receive 8 individually administered sessions of either (a) imaginal exposure (IE), (b) in vivo exposure (IVE), (c) IE combined with IVE (IE/IVE), or (d) IE/IVE combined with CR (IE/IVE/CR). There were fewer patients with PTSD in the IE/IVE/CR (31%) condition than the IE (75%), IVE (69%), and IE/IVE (63%) conditions at a 6-month follow-up assessment. The IE/IVE/CR condition resulted in larger effect sizes than each of the other conditions in terms of PTSD and depressive symptoms. These findings suggest that optimal treatment outcome may be achieved by combining CR with exposure therapy in treating PTSD patients.