Francine Shapiro Library: EMDR Bibliography
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1. Keller, B., Stevens, L. C., Boyce, K., Lui, C., & Murray, J. (2011). Bilateral eye movements and EEG coherence during positive memories: Implications for PTSD and EMDR. Presentation at the American Psychological Association Conference, Washington, DC.
The purpose of this study was to investigate the role of bilateral eye movements in the processing of long-term emotional memories, especially as it pertains to the treatment method for PTSD known as EMDR. EMDR utilizes methods similar to cognitive therapy and exposure but also employs saccadic eye movements to facilitate the treatment. The saccadic eye movements are theorized by Shapiro and others to decrease emotional valence and vividness of episodic memories allowing for easier reprocessing. There remains some disagreement as to the actual role and importance of the saccadic eye movements as well as to the neurological effects of EMDR. This study used EEG power-spectral analysis and measures of interhemispheric coherence on 30 individuals who underwent one of three conditions while recalling positive episodic memories. The 3 conditions were (1) a solid black dot with no eye movement (control), (2) a low frequency color changing dot with no eye movement, and (3) a bilateral eye movement condition simulating EMDR. After a 5’ eyes-open baseline, participants experienced one of the three conditions while recalling a positive memory for five 1’ episodes. After each episode, each participant had 19-channel EEGs recorded while they stared ahead eyes opened. EEG data were noise artifacted, power spectral analyzed, and statistically analyzed for interhemispheric coherence differences between conditions for clusters of frontal pole (Fp), frontal (F), central (C), parietal (P), and occipital (O) electrodes. ANCOVA analysis of post-treatment coherence values, with baseline values as the covariate, across conditions showed significantly increased Low Beta (12-20Hz) activity in the Frontal region of the brain during the saccadic eye movements condition compared to the low frequency dot condition (p=.012). Also found were significantly increased Low Theta (4-6Hz) coherence values in the Parietal region of the brain in the low frequency dot condition compared to both the eye fixation (p=.017) and saccadic eye movement (p=.022) conditions. Self reports of memory clarity and vividness indicated significantly increased measures across all conditions. LORETA cortical localization analyses revealed Low Beta (12-20Hz) activation during the saccadic eye movements condition occurring primarily in Brodmanns Area 11 (BA11) and Brodmann Area 25 (BA25) and Low Theta (4-6Hz) activation during the low frequency dot condition focused in BA35 and BA36. LORETA neuroimages are presented. Cortical localizations of increased Low Beta interhemispheric coherence in BA11 (VentroMedial Frontal Cortex) and BA25 (Subgenual Anterior Cingulate Cortex) following bilateral eye movements during the recall of positive memories suggest a synchronization of information processing activities in parts of the frontal cortex involved in planning, reasoning, and decision making (11) and in verbal episodic memory retrieval (25). These functions are consistent with the assigned tasks of review of positive episodic memories in this study. Coincident with this pattern of cortical activation was an obtained increase in memory clarity and vividness during episodic memory retrieval. It is possible that the obtained effects on beta activity were an artifact of eye movements; however, the lack of significantly increased signal coherence at the Fp region and the removal of eye movement artifacts prior to data analysis reduce this possibility. These results provide support for an Interhemispheric Coherence Model as an explanation for the positive effects of Eye Movement Desensitization and Reprocessing of retrieved memories. Additionally, these outcomes suggest that it is the saccadic eye movements, not a repetition of a rhythmic stimulus, that elicits the changes in interhemispheric coherence, and possibly in emotional valence and vividness, highlighting the importance of saccadic eye movements in EMDR.