Possible neural mechanisms of psychotherapy for trauma-related symptoms: cerebral responses to the neuropsychological treatment of post-traumatic stress disorder model individuals

Abstract

Psychotherapy is often effective for treating psychogenic disorders, but the changes that occur in the brain during such treatments remain unknown. To investigate this, we monitored cerebral activity throughout an entire session using a psychotherapeutic technique in healthy subjects. Since post-traumatic stress disorder (PTSD) is a typical psychogenic psychiatric disorder, we used PTSD-model volunteers who had experienced a moderately traumatic event. The technique used as psychotherapy was eye movement desensitisation and reprocessing (EMDR), a standard method for treating PTSD. The oxygenated haemoglobin concentration ([oxy-Hb]), a sensitive index of brain activation, measured using multi-channel near-infrared spectroscopy, revealed changes in [oxy-Hb] in the superior temporal sulcus (STS) and orbitofrontal cortex (OFC). During a vital therapeutic stage, a significant reduction in the activation by forced eye movements was observed in the right STS, and a trend toward a reduction in the left OFC. The hyperactivation of the right STS on the recall of unpleasant memories, and its normalisation by eye movements, seem to reflect an important neural mechanism of the psychotherapy. These findings suggest that psychotherapy for traumatic symptoms involves brain regions related to memory representation and emotion, and possibly those that link memory and emotion, such as the amygdala.

Figure 1. Changes in heart rate during the session (n = 6; data on one subject were not available).

Visual global inspection reveals a gradual decrease in heart rate through the whole session, which suggests a normalization of autonomic hyperarousal. Detailed inspection shows a temporal increase in heart rate upon recall of unpleasant memories. During the second section which focused on the unpleasant memories, heart rate reached the highest level, and then it rapidly decreased to a normal level in the third section. Abscissa: time (minutes). Ordinate: heart rate (beats per minute).

Figure 2. An example of the change in [oxy-Hb] during a session of desensitization using eye movements.

Graph shows an example of the change in [oxy-Hb] levels from 20th to 26th minute in channel 43 (superior temporal sulcus, STS), in one subject (No. 6). The horizontal axis shows the passage of time (seconds) from the start. The light shading in the graph shows the period of eye movements (EMs), usually 20–30 seconds. The [oxy-Hb] level increased rapidly upon recall of an unpleasant memory, and then it suddenly decreased as soon as the EM started. As this process was repeated, the baseline [oxy-Hb] level gradually decreased. The other subjects also demonstrated a similar pattern of [oxy-Hb] changes. Abscissa: time (second). Ordinate: haemoglobin concentration (m(mol/l)•mm).

Figure 3. Mean [oxy-Hb] levels under Recall and EM conditions in the superior temporal sulcus (STS), the orbitofrontal cortex (OFC), and the dorsolateral prefrontal cortex (DLPFC).

Mean change in [oxy-Hb] levels under each condition ([Recall condition], [EM condition]) in the left and right STS, the OFC and the DLPFC are shown. Repeated ANOVA revealed significant effects of the conditions in the right STS [F (1, 6) = 6.482, p = 0.044, ηp2 = 0.519] (p < 0.05) and the left OFC [F (1, 6) = 4.407: p = 0.081, ηp2 = 0.423] (p < 0.1). The post hoc test for multiple comparisons revealed significant differences during the second section in the right STS (p = 0.024, p < 0.05) and the left OFC (p = 0.084, p < 0.1). No significant differences were observed in the left STS, the right OFC, the left DLPFC or the right DLPFC. Ordinate: haemoglobin concentration (m(mol/l)•mm).

Figure 4. The schema of the study procedure.

The NIRS measurement and its relation to the EMDR sessions are shown. Thick line indicates the monitoring using NIRS.

Figure 5. The position of the NIRS probe and the area measured (Tsuzuki et al.58).