Anke Karl

A meta-analysis of structural brain abnormalities in PTSD.

This series of meta-analyses examined structural abnormalities of the hippocampus and other brain regions in persons with PTSD compared to trauma-exposed and non-exposed control groups. The findings were significantly smaller hippocampal volumes in persons with PTSD compared to controls with and without trauma exposure, but group differences were moderated by MRI methodology, PTSD severity, medication, age and gender. Trauma-exposed persons without PTSD also showed significantly smaller bilateral hippocampal compared to non-exposed controls. Meta-analyses also found significantly smaller left amygdala volumes in adults with PTSD compared to both healthy and trauma-exposed controls, and significantly smaller anterior cingulate cortex compared to trauma-exposed controls. Pediatric samples with PTSD exhibited significantly smaller corpus callosum and frontal lobe volumes compared to controls, but there were no group differences in hippocampal volume. The overall findings suggested a dimensional, developmental psychopathology systems model in which: (1) hippocampal volumetric differences covary with PTSD severity; (2) hippocampal volumetric differences do not become apparent until adulthood; and (3) PTSD is associated with abnormalities in multiple frontal-limbic system structures.

Reorganization of Motor and Somatosensory Cortex in Upper Extremity Amputees with Phantom Limb Pain

Phantom limb pain (PLP) in amputees is associated with reorganizational changes in the somatosensory system. To investigate the relationship between somatosensory and motor reorganization and phantom limb pain, we used focal transcranial magnetic stimulation (TMS) of the motor cortex and neuroelectric source imaging of the somatosensory cortex (SI) in patients with and without phantom limb pain. For transcranial magnetic stimulation, recordings were made bilaterally from the biceps brachii, zygomaticus, and depressor labii inferioris muscles. Neuroelectric source imaging of the EEG was obtained after somatosensory stimulation of the skin overlying face and hand. Patients with phantom limb pain had larger motor-evoked potentials from the biceps brachii, and the map of outputs was larger for muscles on the amputated side compared with the intact side. The optimal scalp positions for stimulation of the zygomaticus and depressor labii inferioris muscles were displaced significantly more medially (toward the missing hand representation) in patients with phantom limb pain only. Neuroelectric source imaging revealed a similar medial displacement of the dipole center for face stimulation in patients with phantom limb pain. There was a high correlation between the magnitude of the shift of the cortical representation of the mouth into the hand area in motor and somatosensory cortex and phantom limb pain. These results show enhanced plasticity in both the motor and somatosensory domains in amputees with phantom limb pain.

Meta-analytic review of event-related potential studies in post-traumatic stress disorder

In recent years there has been an accumulation of studies that have utilized the measurement of event-related potentials (ERP) to examine the neuroelectric correlates of hypothesized alterations in information processing in persons with post-traumatic stress disorder (PTSD). The objective of this meta-analysis was to summarize the findings of ERP PTSD research, including studies that have examined P50 auditory sensory gating, augmenting-reducing P200, and P300 in target detection oddball tasks. The results suggest that persons with PTSD exhibit alterations in the amplitude and latency of ERP within these paradigms that support the hypothesis that changes in information processing can accompany PTSD. The results were also consistent with recent cognitive neuropsychological findings in PTSD research.

The relationship of perceptual phenomena and cortical reorganization in upper extremity amputees

In this study 16 unilateral upper extremity amputees participated in a comprehensive psychophysiological examination that included the assessment of painful and non-painful phantom and stump sensations, thermal and electric perception as well as two-point discrimination thresholds, the detailed analysis of referred sensation and the measurement of reorganizational changes in primary somatosensory cortex using neuroelectric source imaging. Reorganization of the primary somatosensory cortex was associated with increased habitual phantom limb pain, telescoping, non-painful stump sensations and painful referred sensation induced by painful stimulation. It was unrelated to non-painful phantom sensations, non-painful referred sensation elicited by painful or non-painful stimulation, painful referred sensation elicited by non-painful stimulation, perception thresholds and stump pain. These data substantiate the hypothesis that painful and non-painful phantom phenomena are mediated by different neural substrates.

Examining the Factor Structures of the Five Facet Mindfulness Questionnaire and the Self-Compassion Scale

The five facet mindfulness questionnaire (FFMQ; Baer, Smith, Hopkins, Krietemeyer, & Toney, 2006) and the self-compassion scale (SCS; Neff, 2003) are widely used measures of mindfulness and self-compassion in mindfulness-based intervention research. The psychometric properties of the FFMQ and the SCS need to be independently replicated in community samples and relevant clinical samples to support their use. Our primary aim was to establish the factor structures of the FFMQ and SCS in individuals with recurrent depression in remission, since mindfulness-based cognitive therapy (MBCT) was developed as a treatment for preventing depressive relapse. In order to determine the consistency across populations, we examined the factor structures of the FFMQ and SCS in 3 samples: (1) a convenience sample of adults, (2) a sample of adults who practice meditation, and (3) a sample of adults who suffer from recurrent depression and were recruited to take part in a trial of MBCT. Confirmatory factor analyses (CFAs) showed that a 4-factor hierarchical model of the FFMQ best fits the community sample and the clinical sample but that a 5-factor hierarchical model of the FFMQ best fits the meditator sample. CFA did not endorse the SCS 6-factor hierarchical structure in any of the 3 samples. Clinicians and researchers should be aware of the psychometric properties of the FFMQ to measure mindfulness when comparing meditators and nonmeditators. Further research is needed to develop a more psychometrically robust measure of self-compassion.

Posttraumatic Growth in Accident Survivors: Openness and Optimism as Predictors of Its Constructive or Illusory Sides

Posttraumatic growth (PTG), the phenomenon of self-reported positive outcomes of trauma, is assumed to consist of two sides: a constructive and an illusory side. This study investigates the relationship between PTG and its possible illusory and constructive predictors, as well as the moderating role of posttraumatic stress disorder (PTSD) severity. One-hundred two motor vehicle accident (MVA) survivors with full, subsyndromal, and without PTSD were assessed by multiple psychometric measures targeting PTSD severity, posttraumatic growth, optimism, and openness to experience. Hierarchical regression analysis yielded differential interaction effects between PTSD severity and optimism, as well as openness facets pointing to the moderating role of PTSD severity in the prediction of an illusory and a constructive factor in PTG.

Neuroelectric source imaging of steady-state movement-related cortical potentials in human upper extremity amputees with and without phantom limb pain

&NA; Whereas several studies reported a close relationship between changes in the somatotopic organization of primary somatosensory cortex and phantom limb pain, the relationship between alterations in the motor cortex and amputation‐related phenomena has not yet been explored in detail. This study used steady‐state movement‐related cortical potentials (MRCPs) combined with neuroelectric source imaging to assess the relationship of changes in motor cortex and amputation‐related phenomena such as painful and non‐painful phantom and residual limb sensations, telescoping, and prosthesis use. Eight upper limb amputees were investigated. A significant positive relationship between reorganization of the motor cortex (distance of the MRCP source location from the mirrored source for hand movement) and phantom limb pain was found. Non‐painful phantom sensations as well as painful and non‐painful residual limb sensations were unrelated to motor cortical reorganization. A higher amount of motor reorganization was associated with less daily prosthesis use, which also tended to be related to more severe phantom limb pain. These results extend previous findings of a positive relationship between somatosensory reorganization and phantom limb pain to the motor domain and suggest a potential positive effect of prosthesis use on phantom limb pain and cortical reorganization.

A neural substrate for nonpainful phantom limb phenomena.

&NA; Activity in the cerebral cortex associated with non‐painful phantom limb sensation was studied in 14 upper extremity amputees. In four subjects, repetitive tactile stimulation of the digits or the lower corner of the mouth elicited non‐painful phantom sensation in the amputated limb, in the remaining 10 patients no sensation could be evoked. Neuroelectric source imaging revealed significantly elevated activity in SI and posterior parietal cortex, and significantly decreased activity in ipsilateral SII cortex when referred sensations were present. However, nonpainful referred phantom sensations were not associated with a shift of the cortical representation of the mouth into the hand region, as previously suggested. Non‐painful phantom limb experiences seem to have widely distributed neural networks in multiple cortical regions.

Distinct brain networks in recognition memory share a defined region in the precuneus

Current models of recognition memory performance postulate that there are two fundamentally distinct retrieval processes, i.e. recollection and familiarity. This view has been challenged and little is known from human research about the functional connectivity of the brain areas involved in these processes. In our study we used a Remember‐Know procedure to assess the functional connectivity of brain regions under recognition memory in 30 healthy adults. Using functional magnetic resonance imaging, we analysed the blood oxygen level‐dependent responses during correct Remember, correct Know, correct Rejection and missed responses of the subjects during recognition of non‐emotional nouns. One activation cluster was found in the left precuneus associated with both recollection and familiarity answers. To acquire information about the way in which activity in one brain region modulates activity in another brain region in response to the active task, we performed a psychophysiological interaction analysis with the left precuneus as a seed region. This analysis revealed functionally distinct networks of brain areas underlying recollection and familiarity. Furthermore, we discuss the differential involvement of the hippocampus in a recollection network as compared with a familiarity network. In summary, our results further strengthen the assumptions of a dual‐process view of recognition memory [e.g. H. Eichenbaum et al. (2007) Annual Review of Neuroscience, 30, 123–152; A.P. Yonelinas (2001) Philosophical Transactions of the Royal Society London B Biological Sciences, 356, 1363–1374] and add empirical findings about the functional interconnectivity of brain regions supporting either recollection or familiarity.

Neural correlates of posttraumatic growth after severe motor vehicle accidents.

Frontal brain asymmetry has been associated with emotion- and motivation-related constructs. The authors examined the relationship between frontal brain asymmetry and subjective perception of posttraumatic growth (PTG) after severe motor vehicle accidents (MVAs). Eighty-two survivors of MVAs completed self-report measures of PTG, trait and state affect, and diagnostic interviews assessing clinical status, and underwent measurement of resting electroencephalographic activity. As predicted, increased relative left frontal activation was significantly related to PTG, even when statistically controlling for dispositional positive affect. The authors assume that approach-related motivational tendencies associated with higher relative left frontal brain activity may be involved in the process and outcome of PTG.