Electrophysiological abnormalities in PTSD

The impact of posttraumatic stress disorder on event-related potentials in affective and non-affective paradigms: A systematic review with meta-analysis

Post-traumatic stress disorder (PTSD) is associated with neural processing deficits affecting early automatic and later conscious processing. Event-related Potentials (ERPs) are high resolution indices of automatic and conscious processing, but there are no meta-analyses that have examined automatic and conscious ERPs in PTSD across multiple paradigms. This systematic review examined 69 studies across affective and non-affective auditory and visual paradigms. Individuals with PTSD were compared to trauma-exposed and non-trauma controls on ERPs reflecting automatic (N1, P1, N2, P2) and conscious (P3, LPP) processing. Trauma exposure was associated with increased automatic ERP amplitudes to irrelevant auditory information. PTSD further showed increased automatic and conscious allocation of resources to affective information, reduced automatic attending and classification as well as reduced attention processing and working memory updating of non-affective information. Therefore, trauma exposure is associated with enhanced early processing of incoming stimuli, and PTSD with enhanced processing of affective stimuli and impaired processing of non-affective stimuli. This review highlights the need for longitudinal ERP studies in PTSD, adopting standardized procedures and methodological designs.

Closed Loop Deep Brain Stimulation for PTSD, Addiction, and Disorders of Affective Facial Interpretation: Review and Discussion of Potential Biomarkers and Stimulation Paradigms

The treatment of psychiatric diseases with Deep Brain Stimulation (DBS) is becoming more of a reality as studies proliferate the indications and targets for therapies. Opinions on the initial failures of DBS trials for some psychiatric diseases point to a certain lack of finesse in using an Open Loop DBS (OLDBS) system in these dynamic, cyclical pathologies. OLDBS delivers monomorphic input into dysfunctional brain circuits with modulation of that input via human interface at discrete time points with no interim modulation or adaptation to the changing circuit dynamics. Closed Loop DBS (CLDBS) promises dynamic, intrinsic circuit modulation based on individual physiologic biomarkers of dysfunction. Discussed here are several psychiatric diseases which may be amenable to CLDBS paradigms as the neurophysiologic dysfunction is stochastic and not static. Post-Traumatic Stress Disorder (PTSD) has several peripheral and central physiologic and neurologic changes preceding stereotyped hyper-activation behavioral responses. Biomarkers for CLDBS potentially include skin conductance changes indicating changes in the sympathetic nervous system, changes in serum and central neurotransmitter concentrations, and limbic circuit activation. Chemical dependency and addiction have been demonstrated to be improved with both ablation and DBS of the Nucleus Accumbens and as a serendipitous side effect of movement disorder treatment. Potential peripheral biomarkers are similar to those proposed for PTSD with possible use of environmental and geolocation based cues, peripheral signs of physiologic arousal, and individual changes in central circuit patterns. Non-substance addiction disorders have also been serendipitously treated in patients with OLDBS for movement disorders. As more is learned about these behavioral addictions, DBS targets and effectors will be identified. Finally, discussed is the use of facial recognition software to modulate activation of inappropriate responses for psychiatric diseases in which misinterpretation of social cues feature prominently. These include Autism Spectrum Disorder, PTSD, and Schizophrenia-all of which have a common feature of dysfunctional interpretation of facial affective clues. Technological advances and improvements in circuit-based, individual-specific, real-time adaptable modulation, forecast functional neurosurgery treatments for heretofore treatment-resistant behavioral diseases.

Information Processing Bias in Post-traumatic Stress Disorder

This review considers theory and evidence for abnormal information processing in post-traumatic stress disorder (PTSD). Cognitive studies have indicated sensitivity in PTSD for traumatic information, more so than general emotional information. These findings were supported by neuroimaging studies that identify increased brain activity during traumatic cognition, especially in affective networks (including the amygdala, orbitofrontal and anterior cingulate cortex). In theory, it is proposed that traumatic cognition may interfere with neutral cognition and there is evidence of abnormal neutral stimulus processing in PTSD. Firstly, PTSD patients perform poorly on a variety of neuropsychology tasks that involve attention and memory for neutral information. The evidence from event-related potentials and functional neuroimaging also indicates abnormal results in PTSD during neutral stimulus processing. The research evidence generally provides support for theories of trauma sensitivity and abnormal neutral stimulus processing in PTSD. However, there is only tentative evidence that trauma cognition concurrently interferes with neutral cognition. There is even some evidence that traumatic or novelty arousal processes can increase the capacity for attentive processing, thereby enhancing cognition for neutral stimulus information. Research on this topic has not yet fully explored the mechanisms of interaction between traumatic and neutral content in the cognitive dynamics of PTSD.

Reduced mismatch negativity in posttraumatic stress disorder: a compensatory mechanism for chronic hyperarousal?

Mismatch Negativity (MMN) is yet poorly understood in the context of Posttraumatic Stress Disorder (PTSD, e.g. [Morgan 3rd, C.A., Grillon, C., 1999. Abnormal mismatch negativity in women with sexual assault-related posttraumatic stress disorder. Biol. Psychiatry 45, 827-832.]). PTSD symptoms like hyperarousal, emotional pressure and avoidance may interfere with pre-attentive sensory processing. We tested this in an optimized MMN design [Näätänen, R., Pakarinen, S., Rinne, T., Takegata, R. (2004) The mismatch negativity (MMN): towards the optimal paradigm. Clin. Neurophysiol. 115: 140-144.] with PTSD victims and a control group without PTSD. A group of PTSD subjects was compared with gender and age-matched, healthy comparison subjects without PTSD. A "memory trace" was elicited by frequently presented "standard" auditory stimuli (50% occurrence) of 1 kHz, 75 ms duration, intermittently with 8 rare "deviants", which differed in frequency (higher/lower), intensity (louder/softer), duration (shorter), direction (left/right) or by the presence of a gap in the sound. During presentation of tones a silent film was shown. Psychometric data were collected by SCID, BSI, Attentiveness Inventory, Edinburgh Handedness Questionnaire, and the PTSD Screening Scale by Breslau et al. [Breslau, N., Peterson, E.L., Kessler, R.C., Schultz, L.R. (1999) Short screening scale for DSM-IV posttraumatic stress disorder. Am. J. Psychiatry 156: 908-911.]. Group comparisons of the MMN were performed for left/right-frontal/temporal, and for midline electrode sites. A good differentiation of both groups was found in psychometric and electrophysiological data. The PTSD group revealed on most BSI scales enhanced values of psychic aberration. The amplitude of the MMN was significantly reduced in the PTSD compared to non-PTSD subjects. MMN was significantly correlated with the total PTSD score. The data suggest a reduction in pre-attentive auditory sensory memory in PTSD due to specific symptom variables such as hyperarousal, sleeplessness, impaired concentration and a general enhanced excitation of the nervous system. This protective inhibition is thought to be a fine-tuning process in PTSD in order to prevent arousal overload.

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.

Abnormal frontal and parietal activity during working memory updating in post-traumatic stress disorder

This study used event-related potentials (ERPs) to investigate the timing and scalp topography of working memory in post-traumatic stress disorder (PTSD). This study was designed to investigate ERPs associated with a specific working memory updating process. ERPs were recorded from 10 patients and 10 controls during two visual tasks where (a) targets were a specific word or (b) targets were consecutive matching words. In the first task, nontarget words are not retained in working memory. In the second task, as in delay-match-to-sample tasks, a non-target word defines a new target identity, so these words are retained in working memory. This working memory updating process was related to large positive ERPs over frontal and parietal areas at 400-800 ms, which were smaller in PTSD. Estimation of cortical source activity indicated abnormal patterns of frontal and parietal activity in PTSD, which were also observed in regional cerebral blood flow [Clark, C.R., McFarlane, A.C., Morris, P., Weber, D.L., Sonkkilla, C., Shaw, M., Marcina, J., Tochon-Danguy, H., Egan, G., 2003. Cerebral function in posttraumatic stress disorder during verbal working memory updating: a positron emission tomography study. Biological Psychiatry 53, 474-481]. Frontal and parietal cortex are known to be involved in distributed networks for working memory processes, interacting with medial temporal areas during episodic memory processes. Abnormal function in these brain networks helps to explain everyday concentration and memory difficulties in PTSD.

Electroencephalographic comparison of veterans with combat-related post-traumatic stress disorder and healthy subjects

Various investigations prove the biological basis for post-traumatic stress disorder (PTSD). There are only a few quantitative electroencephalographic (qEEG) studies of patients with PTSD. The aim of this investigation is to find out whether there are differences in qEEG parameters between PTSD patients and healthy subjects. The experimental group was comprised of 18 veterans with PTSD, and 20 healthy non-veterans were included in the control group. After informed consent was obtained, they were investigated by qEEG recordings. The artifact-free EEG epoch was analyzed by fast Fourier transformation (FFT). Power values of particular frequency bands (delta, theta, alpha 1, alpha 2, beta 1, beta 2) were observed on the regions: Fp I, Fp2, F3, F4, F7, F8, C3, C4, T3, T4, T5, T6, P3, P4, O1 and O2. PTSD patients had increased theta activity over central regions, and increased beta activity. Beta 1 activity increased over frontal, central and left occipital regions; beta 2 activity increased over frontal regions. No significant differences were noted between the PTSD and control group in delta and alpha activity. These results suggest a neurobiological basis for PTSD. Increased theta activity may help to explain changes in hippocampal volume. Various explanations (cortical hyperexcitability, prolonged wakefulness, or attention disturbances) have been offered for the beta activity increase observed in PTSD subjects.