MEG Correlates during Affective Stimulus Processing in Posttraumatic Stress Disorder

Abstract

In the present thesis, study I focuses on the relationship between retrospectively reported childhood experiences and psychiatric diagnoses in adult life, study II and study III covers a wide range of affective stimuli and procedures focusing on special features of emotional processing in PTSD: we implemented a visual paradigm to investigate cortical activation patterns during processing of high arousing (pleasant and unpleasant) as compared to low (neutral) arousing pictures in PTSD patients, in schizophrenia patients and healthy controls using magnetoencephalography; in addition to magnetocortical data we examined subjective ratings, heart rate and startle responses. In studies II and III, standardized colored picture stimuli from the International Affective Picture Systems are used. The neural processing underlying emotional information processing in PTSD patients, in schizophrenia patients and healthy participants is studied and the origin of neuromagnetic activity in the brain is modeled by means of magnetic source imaging (MSI). PTSD patients showed a differential sensitivity for the early time windows for high arousing unpleasant pictures. Avoidance symptoms in PTSD patients were negatively correlated with the difference unpleasant minus neutral for the N1m time window suggesting that amplified responses for neutral pictures were negatively correlated with high avoidance scores. PTSD patients showed for the late components increased activity for high arousing pictures suggesting cortical facilitation in attentional processes. Heart rate responses differed significantly among PTSD patients, schizophrenia patients and control participants showing sustained heart rate acceleration for high arousing unpleasant pictures in PTSD patients. Taken together, the earlier amplification for neutral pictures in PTSD patients such as found in the range of the N1m component may indicate initial cortical inhibition of magnetic fields for visual features that are motivationally significant may be associated with PTSD symptoms. As evidenced by the MNE, high arousing pictures elicited greater activity than low arousing (neutral) pictures did in PTSD patients over frontal and frontoparietal cortical networks for the early P3m window, over anterior and posterior parietal regions for the late P3m window and hereby representing differences among groups. There was evidence of failure in PTSD patients but not in schizophrenia patients to show a specific sensitivity to emotional modulation of visual cortex in the range of the N1m time window. Furthermore, source space projection from subsequent time windows such as early and late P3m revealed specific enhancement of electro-cortical activity in PTSD over prefrontal and parietal cortical areas. This finding may reflect increased allocation of attentional resources to arousing stimuli over time in PTSD patients. Based on these observations elements of a model of human emotional stimulus processing in PTSD is proposed.