Hemodynamic responses of eye movement desensitization and reprocessing in posttraumatic stress disorder

Abstract

Eye movement desensitization and reprocessing (EMDR) is an effective psychological intervention for posttraumatic stress disorder (PTSD). Trauma-related recall (Recall) with eye movements (EMs) is thought to reduce distress. However, the neural mechanisms underlying this process remain unknown. Thirteen patients with PTSD received EMDR treatment over the course of 2–10 weeks. We assessed the change in hemoglobin concentration in the lateral prefrontal cortex (PFC) during Recall with and without EM using multi-channel near-infrared spectroscopy (NIRS). Clinical diagnosis and improvement were evaluated using the Clinician-Administered PTSD Scale. Recall with EM was associated with a significant decrease in oxygenated hemoglobin concentration ([oxy-Hb]) in the lateral PFC as compared with Recall without EM. Longitudinally, [oxy-Hb] during Recall significantly decreased and the amount of decrease was significantly correlated with clinical improvement when the post-treatment data was compared with that of the pre-treatment. Our results suggest that performing EM during Recall reduces the over-activity of the lateral PFC, which may be part of the biological basis for the efficacy of EMDR in PTSD. NIRS may be a useful tool for objective assessment of psychological intervention in PTSD.

Introduction

Posttraumatic stress disorder (PTSD) is a trauma-related anxiety disorder characterized by the subjective re-experiencing of a traumatic event, avoidance of stimuli associated with the trauma or numbing of general responsiveness, and increased arousal. No definitive pharmacological treatment for PTSD has yet been established, and current pharmacological treatment is sometimes insufficient to provide complete remission of PTSD (for a review, see Friedman, 1988). Thus, the recommended treatment for PTSD includes a combination of various medications and psychotherapies. Eye movement desensitization and reprocessing (EMDR) is an effective therapy designed to alleviate PTSD symptoms (Shapiro, 1989). In EMDR treatment, patients visualize the most salient aspect of a traumatic memory while making saccade-like eye movements, and a repetitive series of this concurrent action results in changes in the cognitive processing of the memory and cessation of intrusive thoughts (Shapiro, 1989). After this process decreases the distress of traumatic memory recall, the repetitions of the positive thought recall with eye movements can serve to reinforce the positive cognition. Consequently, the subjective distress is reduced and the validity of the positive cognition increases enough to improve the PTSD symptoms (Shapiro, 1989). The eye movement procedure and the free association after traumatic event recall distinguish EMDR from other standard prolonged exposure protocols. The effectiveness of EMDR in subjects with trauma-related disorders has been demonstrated in several case studies of clinical practices (Wolpe and Abrams, 1991, Lipke and Botkin, 1993), controlled studies (Forbes et al., 1994, Wilson et al., 1994, Van der Kolk et al., 2007) and meta-analyses (Van Etten and Taylor, 1998, Seidler and Wagner, 2006).

Recently, there has been an accumulation of studies using functional neuroimaging to understand the brain mechanisms underlying psychological as well as pharmacological treatment effects in patients with psychiatric disorders (reviewed in Linden, 2006). To date, several studies have examined changes in brain function before and after an EMDR treatment course. Lamprecht et al. (2004) used an event-related potential index of involuntary attention to salient events (P3a) and reported that PTSD patients showed a significant reduction in the P3a amplitude after EMDR compared with a control group receiving a sham treatment. A case report using single photon emission computed tomography (SPECT) showed that the left frontal lobe and anterior cingulate cortex (ACC) showed greater activation during traumatic memory recall after EMDR treatment than before treatment (Levin et al., 1999). Another SPECT study examining delayed-onset PTSD subjects showed decreases in the left and right occipital lobe, left parietal lobe, and right precentral frontal lobe as well as significantly increased perfusion in the left inferior frontal gyrus (Lansing et al., 2005). These previous studies examined the brain function pre- and post-EMDR treatment course. However, to our knowledge, no study has examined changes in brain function during the EMDR treatment course. Thus, we examined the real-time changes during one EMDR session using tasks patterned by EMDR procedures, and we also examined the longitudinal changes in brain function and the level of distress caused by PTSD symptoms in the course of EMDR treatment.

In this study, we used multi-channel near-infrared spectroscopy (NIRS) in order to measure changes in the brain function. NIRS is a functional neuroimaging technology that enables the noninvasive detection of spatiotemporal characteristics of brain function (Strangman et al., 2002a, Strangman et al., 2003, Boas et al., 2004, Huppert et al., 2006), by measuring regional cerebral blood volume (rCBV) in terms of the relative concentrations of oxyhemoglobin ([oxy-Hb]) and deoxyhemoglobin ([deoxy-Hb]) (Suto et al., 2004). NIRS uses two different wavelengths of near-infrared light. A portion of the near-infrared light is absorbed by hemoglobin during its course from the source of the near-infrared light to the detector (Watanabe et al., 1996). Based on the absorption characteristics, the changes in [oxy-Hb] and [deoxy-Hb] can be calculated using the modified Beer–Lambert law. Values are calculated as the product of hemoglobin concentration and optical path length. Activation of a certain brain area causes blood vessel dilation and increases the regional cerebral blood volume. This blood volume increase is more than the oxygen consumption in the activated region (Gsell et al., 2000). As a result, NIRS can detect brain activation as an increase of [oxy-Hb] (Strangman et al., 2002b). We adopted NIRS as a measurement instrument in this study because of the following reasons. First, the high temporal resolution of NIRS is useful in characterizing the time course of prefrontal cortex (PFC) activity of psychiatric disorders (Suto et al., 2004, Kameyama et al., 2006). Second, the portability and compactness of NIRS's apparatus enable the subjects to be examined in a natural sitting position, avoiding the discomfort of loud noises or physical restraint, more than other imaging methods such as PET, SPECT and fMRI (Strangman et al., 2002a). This enabled the subjects to be measured during tasks patterned by real EMDR procedures without contamination of the effect of being measured in an unnatural posture. Third, repeated measurements in an individual are possible with NIRS since it is a noninvasive measurement (Kameyama et al., 2006, Kono et al., 2007), the set-up for the measurement is very easy, and the cost of the measurement is much lower than other neuroimaging modalities. Accordingly, NIRS has the potential to be applied in clinical testing at short-term multiple time-points (Kono et al., 2007) (e.g., at each time in the treatment session during the treatment course). Indeed, NIRS can measure only the cortical surface of the brain. Accordingly, it cannot assess medial PFC including ACC and amygdala where PET and fMRI studies have shown a reduced activation in the medial PFC and an exaggerated response in the amygdala during trauma-related stimuli in PTSD patients (Bremner et al., 1999a, Bremner et al., 1999b, Lanius et al., 2001, Shin et al., 2001, Shin et al., 2004). However, NIRS allowed us to make a dynamic research model examining brain function during tasks patterned by EMDR procedures, and through the use of NIRS we could measure real-time changes in hemoglobin concentration levels not possible with the alternatives. Thus, although the neuroanatomical foci of NIRS are different from that of PET, SPECT or fMRI studies due to the methodological and technological differences described above, NIRS may be suitable for investigating changes in the brain function associated with EMDR treatment in PTSD.

In a previous study, we reported that subjects with PTSD showed a significant increase of [oxy-Hb] in the lateral PFC during trauma-related visual stimuli (Matsuo et al., 2003). Additionally, our preliminary NIRS study in healthy subjects showed that emotional memory recall produced a significant [oxy-Hb] increase in the lateral PFC (Ohtani et al., 2005). In a different study, Stickgold (2002) posited that the repetitive redirecting of attention during eye movement in EMDR induces a neurobiological state similar to that of REM sleep. Subjects who maintained steady REM sleep during brain scanning showed less regional cerebral blood flow in a vast area of dorsolateral PFC (Maquet et al., 1996). Thus, we hypothesized that, cross-sectionally, trauma-related recall might increase [oxy-Hb] in the lateral PFC and trauma-related recall with eye movement that is the task patterned by EMDR procedures would bring significant changes of [oxy-Hb] in the lateral PFC. In addition, longitudinally, that lateral PFC activity during trauma-related recall at pre-treatment would change through EMDR treatment.

The goal of the present NIRS study was to evaluate changes of the activity in lateral PFC during a repetitive series of trauma-related recall with eye movement condition that was patterned by EMDR protocols, and to monitor longitudinal changes in the activity of lateral PFC associated with an EMDR treatment course in PTSD patients.