Authors
Kana Minamikawa¹,
Shingo Kakigi²,
Masaya Ichii³,
Kazuaki Maeda^4
1Ashiya Counseling Room Root, 4-12 Ohara, Ashiya, Hyogo 659-0092, Japan
²The Joint Graduate School in Science of School Education Hyogo University of Teacher Education, Shimokume 942-1, Kato-city, Hyogo 673-1494, Japan
³Hyogo University of Teacher Education, Shimokume 942-1, Kato-city, Hyogo 673-1494, Japan
⁴Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe, Hyogo 658-8501, Japan

Previous studies have investigated the effect of saccadic eye movement (EM). However, eye movement desensitization and reprocessing (EMDR) therapists appear to elicit smooth pursuit EM by instructing clients to follow their fingers. Minamikawa et al. (2022, 2024) hypothesized the effect of EMDR is induced by saccadic EM and measured eye tracks and analyzed the type of EM. Participants followed a dot moving back and forth for 30 rounds, in 5 different speeds: 0.4, 0.6, 0.8, 1.0, and 1.2 Hz.
Experiment 1 (no recall): 9 healthy adults’ eye tracks made saccadic EMs at faster than 0.6 Hz. Smooth pursuit EMs was induced only at 0.4 Hz, but there was great individual variation.
Experiment 2 (recall): 11 healthy adult participants recalled a disturbing event and simultaneously track a visual target. Subjective Units of Discomfort Scale (SUD) were measured before and after EMs, the following day and one week later. Participants mainly made saccadic EMs at faster than 1.0 Hz but smooth pursuit EMs at 0.4 Hz. SUD was attenuated in all speed conditions, but a certain degree of saccadic EM occurrence was needed. Comparison of two experiments suggest when a visual target moves at 1.0 or 1.2Hz, EMDR can be effective and saccadic EM is necessary for processing negative memory. Furthermore, these results indicated that even if the visual target was inducing pursuit EMs, participants’ eyes were still making saccadic EMs. We consider saccadic EM facilitates REM sleep-like system. Therefore, we suggest 1:1 or 2:1 ratio of finger width to eye-to-finger distance for EMDR therapists to lead a client to make saccadic EM at faster than 1.0Hz.

Learning Objectives
1. Why EMDR works even if therapists appear to elicit smooth pursuit EM.
2. The roll of saccadic EM in EMDR.
3. How to lead a client to make saccadic EM in EMDR.

Authors
Shingo Kakigi¹,
Gakuto Enokibara²,
Masaya Ichii³,
Kazuaki Maeda^4
1The Joint Graduate School in Science of School Education Hyogo University of Teacher Education, Shimokume 942-1, Kato-city, Hyogo 673-1494, Japan
²Graduate School of Science and Technology in Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma, Nara, 630-0192, Japan
⁴Hyogo University of Teacher Education, 942-1, Shimokume, Kato, Hyogo, 673-1494, Japan
⁴Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe, Hyogo 658-8501, Japan

Several studies have mentioned the effectiveness of saccadic eye movement in eye movement desensitization and reprocessing (EMDR). For example, saccades increase interhemispheric interaction or induce REM sleep-like states. Moreover, our studies have revealed that although EMDR therapists instruct clients to follow their fingers, their eyes don’t move smoothly but saccadically [1]. Therefore, we hypothesized that saccades in EMDR contribute to trauma processing by inducing interhemispheric interactions and REM sleep-like states. This study aimed to measure the brain activity during saccade induction with an electroencephalograph and conduct an electrophysiological evaluation analysis. Sixteen undergraduate and graduate students attended. They were instructed to follow a moving dot horizontally on the monitor with their eyes. There were four types of moving with different motions (pursuit or saccade) and speeds (0.4Hz or 1.0Hz). The EEG analysis evaluated β2 and θ waves for interhemispheric interaction and REM sleep-like state, respectively. The results showed that pursuit and saccade at 1.0Hz amplified β2 and θ wave components in the right hemisphere. On the other hand, θ waves showed a tendency for the EEG amplitude of the right hemisphere to increase in a manner dependent on eye movement speed, regardless of the type of eye movement. These results support the interhemispheric interaction hypothesis and REM sleep hypothesis.
Right brain activation by saccades during EMDR may contribute to trauma processing by inducing interhemispheric interactions, changing the focus on memory, and inducing a REM sleep-like state to facilitate the association between trauma and other related memories.

Learning Objectives
1. The mechanism of action of saccades in EMDR.
2. About the interhemispheric interaction hypothesis and the REM sleep hypothesis.
3. Measurement of EEG during eye movements.

References
[1] Minamikawa, K. et al., Japanese Journal of EMDR Research and Practice, 14, 35-45 (2022).