Table 1 Summary of articles included in the systematic review (11 studies)

(Engelhard, van den Hout, Dek, et al., 2011)

Investigate whether double task could provide better

desensitization of the

traumatic memory

Participants with recurrent intrusive/ disturbing visual images (N = 37)

1 group (N = 37)

No control group

Yale-Brown Obsessive Compulsive Scale and SCL-90

Experimental study using computer and behavioural task/measure of an emotionally disturbing auditory memory

Two conditions: recall intrusive images with EM or recall without making eye movements

VAS score on vividness and emotionality

Vividness of intrusive images was lower after recall with eye movement, relative to recall only (t(36) = 2.37, p < .05, d = 0.37), and there was a similar trend for emotionality (t(36) = 2.01, p < .05, d = 0.32).

(Thomaes et al., 2016)

Examine visual and emotional processing brain regions as well as the activity of the DLPFC during the recall of the

traumatic memory recall, with EM relative to recall-only

Participants with current PTSD symptoms (N = 8)

1 group (N = 8)

No control group

Structured clinical interview and

PSS-SR scale

Experimental study using functional magnetic resonance imaging

Two conditions: recall of the traumatic

memories with EM and recall without EM

Neural activation in brain regions in response to memory recall during script-driven imagery

EM during recall, compared to recall only, was associated with reducing activity – i.e., less activation of right amygdala and rostral ACC and connectivity in emotional processing in brain regions (T = 3.499, p-uncorrected < 0.005)

(Sack et al., 2016)

Examine if there is better desensitization

with exposure alone, with a double task, or with a visual fixation task

Participants with current PTSD (N = 139)

EM group (N = 47) and EF group (N = 47)

Control group (EC) (N = 45)

CAPS interview based on the DSM-IV

Randomized clinical trial

Three conditions: eyes moving on the therapist’s moving hand (EM), eyes fixating on the therapist’s non-moving hand (EF), and exposure without explicit visual focus of attention as the control condition (EC)

CAPS scores on PTSD symptoms and

remission of PTSD diagnosis after EMDR session

Larger symptom decrease in EM and EF than in EC (CAPS: EM = 35.8, EF = 40.5, EC = 31.0) and significantly larger effect sizes (EM: d = 2.06, 95% CI: 1.55–2.57, EF: d = 2.58, 95% CI: 2.01–3.11, EC: d = 1.44, 95% CI: 0.97–1.91);

no difference between EM and EF

(Matthijssen et al., 2017)

Investigate whether auditory memories can be targeted with EMDR in PTSD patients

Participants with current PTSD symptoms (N = 30)

1 group (N = 30)

No control group

Clinical psychologist/psychiatrist screening using DSM IV-TR criteria

Experimental study with behavioural task/measure of an emotionally disturbing memory

Three conditions:

to make EM (VT), to count down (AT), or to stare at a non-moving dot (CC)

SUD score on the emotionality of a disturbing image and

reaction time

Emotionality of auditory memory was reduced in the three conditions; however, no difference was found between AT, VT, or the CC [Auditory Memory: [F(2,58) = 2.02, p = .14]; Visual Memory F(2,60) = 0.25, p = .78]

(Matthijssen et al., 2019)

Examine the extent to which emotionality of auditory hallucination memories could be reduced by dual tasking

Participants with current PTSD symptoms (N = 36)

1 group (N = 36)

No control group

PSYRATS-AH questionnaire, BAVQ-R questionnaire, SUD score

Experimental study with behavioural task/measure of an emotionally disturbing auditory memory

Three conditions: visual taxation though EM (VT), auditory taxation by counting out loud (AT), and control condition without any additional task (CC)

SUD score on the emotionality of a disturbing image

The active conditions – i.e., making eye movements or counting out loud – showed stronger effects in reducing emotionality of auditory hallucinations compare to the control condition

[BF1 = 5.8, model 1: AT (pre-post) = VT (pre-post) > CC (pre-post)]

(Matthijssen & van Hout, 2016)

Examine the effects of eye movements on positive verbal imagery after an

EMDR session

Healthy participants (N = 30)

1 group (N = 30)

No control group

\

Experimental study using selected individual negative memory

Two conditions: EM and eyes stationary (ES)

VAS scale on the belief in personality trait

and perception checklist scores

No significant differences between the eye movement and the eyes stationary conditions; eye movements did not diminish or enhance the belief of the positive relevant personality trait (F(1, 35) = 0.071, p = .792)

(Voogd & Phelps, 2020)

Examine whether the impact of a working memory task on extinction learning is greater when cognitive load is increased

Healthy participants exposed to PTSD-induced trauma (n = 75) across three groups

Low-load group (N = 24) and high-load group (N = 27)

Control group (N = 24)

\

Experimental study with induced PTSD using images of snakes associated with peripheral stimulation

Three conditions: low-load condition group, high-load condition group, and without dual task as the control condition

Accuracy scores on a random sequence, SCR response, and reaction times

The conditioned response was stronger in the control group compared to the low-load group [F(1, 46) = 4.24, p = .045, ηp 2 = 0.08] and the high-load group [F(1, 49) = 12.07, p = .001, ηp 2 = 0.20]; also, a stronger cognitive load had a bigger impact on the reduction in the conditioned response compared to the control condition [t(72) = − 3.619, p < .001]

(Leer & Engelhard, 2020)

Examine the effect of induced EM on memory accuracy on a visual discrimination task

Healthy participants (n = 68)

Group for discrimination test day 2 (N = 34) and group for discrimination test day 1 and day 2 (N = 34)

No control group

\

Experimental study with induced trauma using two sets of images and a 2-ms electrocutaneous stimulus

Two conditions: recall with EM condition vs. recall without eye movements condition

Shock occurrence prediction, shock expectancy rating score,

number of false positive responses, and

reaction time of responses

False positive rates in a discrimination task increased in recall with eye movement condition the day after the conditioning phase, compared to the control condition (F(1, 66) = 14.58, p < .001, ηp2 = 0.181)

(van Schie et al., 2019)

Investigated the effects of dual tasks on intrusive memories following analogue trauma

Healthy participants (n = 76)

1 group (N = 76)

No control group

\

Experimental study with induced trauma using word-image association pairs

Three conditions: recall + EM condition, recall + counting condition, and no task (control condition);

two different dual tasks to quantify WM (RIR + EM, RIR + counting, or RIR only

VAS score on vividness and emotionality, response latency score, and choice confidence

Cognitive loads of RIR + EM and RIR + counting were higher than RIR only (BFs10 > 2.81 × 10¹⁷);

hotspot vividness and unpleasantness ratings were not affected by the intervention; WM taxation was not related to decreases in vividness (r = − .19, BF01 = 12.60)

or unpleasantness (r = − .04, BF01 = 6.90)

(van Veen et al., 2020)

Examine if recall + EM results in larger immediate and 24-hour reductions in memory vividness, negative valence, and distress than recall alone

Healthy participants (n = 45)

Recall + EM group (N = 50) and recall only group (N = 50)

No control group

\

Experimental study with induced trauma using negative autobiographical memory

Two conditions: recall with EM vs. recall without EM

VAS score on vividness, negative valence, and distress ratings; SUIS score on tendency and ease of forming visual images in daily life; ACS score; automated reading span

After four sessions, memory was deflated in recall with eye movements –vividness − 0.90 (− 3.10–1.23); negative valence 0.64 (− 0.76–2.14); distress 0.82 (− 1.17–2.86); memory was inflated in recall alone –vividness − 2.84*(− 4.95 to − 0.71), negative valence − 2.13*(− 3.60 to − 0.70), distress − 3.59*(− 5.57 to − 1.58)

After 32 sessions, there was a reduction in both recall conditions for all outcome measures

(Rackham & Lau-Zhu, 2021)

Investigate whether mental imagery of the 9/11 terrorist attacks following media exposure is dampened by taxing working memory

Healthy participants (n = 45)

1 group (N = 45)

No control group

\

Experimental study with PTSD induced using a personally relevant mental image of the 9/11 terrorist attacks

Three conditions:

recall + EM,

recall + Tetris game, and recall only

11-point Likert scale on imagery vividness and emotionality

Compared to recall only, dual-task effects (i.e., recall + Tetris and recall + EM) reduced ratings of vividness and emotionality – recall + Tetris, F(1, 28) = 27.90, p < .001, h2 p = .50, 90% CI = [0.26, 0.64]; recall + EM, F(1, 28) = 37.44, p < .001, h2 p = .57, 90% CI = [0.34, 0.69]; this effect vanished in a follow-up (24 h later) test –recall + Tetris, t(14) = 4.75, p < .001, d = 1.22, and recall + EM, t(14) = 5.82, p < .001, d = 1.51)