Early Affective Processing in Patients with Acute Posttraumatic Stress Disorder: Magnetoencephalographic Correlates

Background: In chronic PTSD, a preattentive neural alarm system responds rapidly to emotional information, leading to increased prefrontal cortex (PFC) activation at early processing stages (<100 ms). Enhanced PFC responses are followed by a reduction in occipito-temporal activity during later processing stages. However, it remains unknown if this neuronal pattern is a result of a long lasting mental disorder or if it represents changes in brain function as direct consequences of severe trauma.Methodology: The present study investigates early fear network activity in acutely traumatized patients with PTSD. It focuses on the question whether dysfunctions previously observed in chronic PTSD patients are already present shortly after trauma exposure. We recorded neuromagnetic activity towards emotional pictures in seven acutely traumatized PTSD patients between one and seven weeks after trauma exposure and compared brain responses to a balanced healthy control sample. Inverse modelling served for mapping sources of differential activation in the brain.Principal Findings: Compared to the control group, acutely traumatized PTSD patients showed an enhanced PFC response to high-arousing pictures between 60 to 80 ms. This rapid prefrontal hypervigilance towards arousing pictorial stimuli was sustained during 120–300 ms, where it was accompanied by a reduced affective modulation of occipito-temporal neural processing.Conclusions: Our findings indicate that the hypervigilance-avoidance pattern seen in chronic PTSD is not necessarily a product of an endured mental disorder, but arises as an almost immediate result of severe traumatisation. Thus, traumatic experiences can influence emotion processing strongly, leading to long-lasting changes in trauma network activation and expediting a chronic manifestation of maladaptive cognitive and behavioral symptoms

Early Affective Processing in Patients with Acute Posttraumatic Stress Disorder: Magnetoencephalographic Correlates

<div><p>Background</p><p>In chronic PTSD, a preattentive neural alarm system responds rapidly to emotional information, leading to increased prefrontal cortex (PFC) activation at early processing stages (<100 ms). Enhanced PFC responses are followed by a reduction in occipito-temporal activity during later processing stages. However, it remains unknown if this neuronal pattern is a result of a long lasting mental disorder or if it represents changes in brain function as direct consequences of severe trauma.</p><p>Methodology</p><p>The present study investigates early fear network activity in acutely traumatized patients with PTSD. It focuses on the question whether dysfunctions previously observed in chronic PTSD patients are already present shortly after trauma exposure. We recorded neuromagnetic activity towards emotional pictures in seven acutely traumatized PTSD patients between one and seven weeks after trauma exposure and compared brain responses to a balanced healthy control sample. Inverse modelling served for mapping sources of differential activation in the brain.</p><p>Principal Findings</p><p>Compared to the control group, acutely traumatized PTSD patients showed an enhanced PFC response to high-arousing pictures between 60 to 80 ms. This rapid prefrontal hypervigilance towards arousing pictorial stimuli was sustained during 120–300 ms, where it was accompanied by a reduced affective modulation of occipito-temporal neural processing.</p><p>Conclusions</p><p>Our findings indicate that the hypervigilance-avoidance pattern seen in chronic PTSD is not necessarily a product of an endured mental disorder, but arises as an almost immediate result of severe traumatisation. Thus, traumatic experiences can influence emotion processing strongly, leading to long-lasting changes in trauma network activation and expediting a chronic manifestation of maladaptive cognitive and behavioral symptoms.</p></div

Visualization of differences between patients and controls with regard to the linear arousal-driven modulation of neural activation during the early time-interval (60–80 ms).

<p>5A) and 5B) as in 3B) with the exception that a greater linear arousal modulation for patients compared to controls is found at predominately bilateral dorsolateral and ventro-central prefrontal dipole locations. Please note that the cluster-level significance has been increased to p<.10. 5C) The regional amplitude of the analyzed dipoles is displayed for patients and control separately with regard to the AROUSAL dimension of the picture (high-arousing, low-arousing picture) only. 5D) The regional amplitude of the analyzed dipoles is displayed for patients and control separately with regard to the VALENCE dimension of the picture (negative, positive picture) only.</p

Visualization of subjective ratings of (A) hedonic valence and (B) emotional arousal across all patients (blue) and controls (red).

<p>Visualization of subjective ratings of (A) hedonic valence and (B) emotional arousal across all patients (blue) and controls (red).</p

Visualization of the linear arousal-driven modulation of neural activation across all participants during the early time-interval (60–80 ms).

<p>A) as in 2A) with the exception that the contrast distribution is projected onto a standard brain shown from the front. It contains mainly bluish colours which indicates linearly decreasing neural activity with increasing arousal of the picture categories visible at predominately right dorsolateral and right and left temporal cortex.</p

Visualization of the linear arousal-driven modulation of neural activation across all participants during the EPN-m time-interval (120–300 ms).

<p>A) In the top row of the first column, neural clusters are displayed that show a cluster-level significance of p<.05 for the linear arousal contrast calculated across all participants. The image was achieved by first calculating the contrast distribution (4, −1, −6, −1, 4) for the linear arousal contrast of PICTURE CATEGORY (HiPos > LoPos > Neut < LoNeg < HiNeg) across all patients and controls with averaged z-values of a cluster containing a center dipole and its five closest neighbours. The contrast distribution was then masked with the significance level topography for this very contrast after 1,000 random permutations of all data sets (subjects x conditions) given a significance criterion of p<.05 and a cluster size of six neighbouring dipoles. The masked contrast distribution, which highlights spatio-temporal clusters (6 dipoles, 120–300 ms) with significant effects on a cluster level, is displayed in z-values and projected onto a standard brain (back view). Reddish coloured areas indicate linearly increasing neural activity with increasing arousal of the picture categories visible at predominately medial occipital cortex areas. Black cylinders visualize the occipital dipole locations used for the second level analysis. Please mind that dipoles within these areas represent the centres of cluster-level significant groups of dipoles. The extent of the area with significant effects is thus bigger than the highlighted region. In the bottom row of the first column, the regional amplitude of the analyzed dipoles with regard to each picture category is displayed across patients and controls. B) as in A) with the exception that the masked contrast distribution projected on a standard brain is shown from the front and indicates a linearly increasing neural activity with increasing arousal of the picture categories at the dorsomedial and right orbitofrontal cortex.</p

Visualization of differences between patients and controls with regard to the linear arousal-driven modulation of neural activation during the EPN-m time-interval (120–300 ms).

<p>A) In the top row of the first column, the neural clusters are displayed that show a cluster-level significance of p<.05 for the differences of patients and controls in the linear arousal contrast. The image was achieved by first calculating the contrast distribution (4, −1, −6, −1, 4, −4, 1, 6, 1, −4) for the interaction of the linear arousal contrast of PICTURE CATEGORY (HiPos > LoPos > Neut < LoNeg < HiNeg) with GROUP (patients, controls) with averaged z-values of a cluster containing a center dipole and its five closest neighbours. The contrast distribution was then masked with the significance level topography for this very contrast after 1,000 random permutations of all data sets (subjects x conditions) given a significance criterion of p<.05 and a cluster size of six. The masked contrast distribution, which highlights spatio-temporal clusters (6 dipoles, 120-300 ms) with significant effects on a cluster level, is displayed in z-values and projected onto a standard brain (back view). Bluish coloured areas indicate a decreased linear U-shaped arousal contrast for the picture categories in patients vs. controls visible at predominately left occipito-temporal areas. Black cylinders visualize the left occipito-temporal dipole locations used for the second level analysis. In the bottom row, the regional amplitude of the analyzed dipoles with regard to each picture category is displayed for patients and controls separately. B) as in A) with the exception that the masked contrast distribution projected on a standard brain is shown from the front and contains mainly reddish colours indicating an enhanced linear arousal modulation in patients vs. controls.</p

Plot displaying the global power of the estimated neural activity across time over all participants and all test sources.

<p>The two a-priori defined time-intervals of interest used for statistical analysis (60–80 ms, 120–300 ms) are marked in gray.</p