Bilateral eye movements enhance the retrieval of episodic memories

The Effect of Eye Movement Desensitization and Reprocessing (EMDR) Therapy on Reducing Craving in Populations with Substance Use Disorder: A Meta-Analysis

Substance use disorder (SUD) significantly impacts public health, economics, and legal systems worldwide. Eye Movement Desensitization and Reprocessing (EMDR) was initially developed in the late 1980s as a therapeutic approach for post-traumatic stress disorder (PTSD), using bilateral stimulation to integrate traumatic memories with calming physiological responses. However, the effectiveness of EMDR in treating SUD remains unclear. This study aims to conduct a systematic review and meta-analysis of the impact of EMDR therapy on craving reduction in individuals with SUD. The search was conducted using databases such as PubMed and Web of Science, focusing on studies that measured craving and employed EMDR interventions. Both random and fixed effects models were used to pool effect sizes, utilizing an R software meta-package (R-4.4.1). The study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The results indicated a significant reduction in cravings among patients undergoing EMDR therapy. Specifically, under the fixed effect model, the standardized mean difference (SMD) was -0.866 with a 95% confidence interval ranging from -1.121 to -0.611 (z = -6.66, p < 0.0001). These findings may demonstrate the significant efficacy of EMDR therapy in decreasing cravings in people with SUD.

Eye movement intervention facilitates concurrent perception and memory processing

A widely used psychotherapeutic treatment for post-traumatic stress disorder (PTSD) involves performing bilateral eye movement (EM) during trauma memory retrieval. However, how this treatment-described as eye movement desensitization and reprocessing (EMDR)-alleviates trauma-related symptoms is unclear. While conventional theories suggest that bilateral EM interferes with concurrently retrieved trauma memories by taxing the limited working memory resources, here, we propose that bilateral EM actually facilitates information processing. In two EEG experiments, we replicated the bilateral EM procedure of EMDR, having participants engaging in continuous bilateral EM or receiving bilateral sensory stimulation (BS) as a control while retrieving short- or long-term memory. During EM or BS, we presented bystander images or memory cues to probe neural representations of perceptual and memory information. Multivariate pattern analysis of the EEG signals revealed that bilateral EM enhanced neural representations of simultaneously processed perceptual and memory information. This enhancement was accompanied by heightened visual responses and increased neural excitability in the occipital region. Furthermore, bilateral EM increased information transmission from the occipital to the frontoparietal region, indicating facilitated information transition from low-level perceptual representation to high-level memory representation. These findings argue for theories that emphasize information facilitation rather than disruption in the EMDR treatment.

Differences Between Consistent and Inconsistent Handedness Remain Consistently Interesting: Ten Years of Research on the Consistency of Handedness With the Edinburgh Handedness Inventory

Almost 10 years ago Prichard et al. (2013) published a literature review on consistency of handedness. They described how consistency of handedness, typically measured by the Edinburgh Handedness Inventory (EHI), predicted outcomes in memory and decision-making paradigms better than direction of handedness. In the last 10 years, new research has extended these findings and added new theoretical perspectives. The goal of this short form review is to highlight and summarize some of these more intriguing findings and to encourage researchers in the fields of memory and decision making to incorporate handedness as a variable in future research.

Bilateral eye movements disrupt the involuntary perceptual representation of trauma-related memories

Bilateral eye movement (EM) is a critical component in eye movement desensitization and reprocessing (EMDR), an effective treatment for post-traumatic stress disorder. However, the role of bilateral EM in alleviating trauma-related symptoms is unclear. Here we hypothesize that bilateral EM selectively disrupts the perceptual representation of traumatic memories. We used the trauma film paradigm as an analog for trauma experience. Nonclinical participants viewed trauma films followed by a bilateral EM intervention or a static Fixation period as a control. Perceptual and semantic memories for the film were assessed with different measures. Results showed a significant decrease in perceptual memory recognition shortly after the EM intervention and subsequently in the frequency and vividness of film-related memory intrusions across one week, relative to the Fixation condition. The EM intervention did not affect the explicit recognition of semantic memories, suggesting a dissociation between perceptual and semantic memory disruption. Furthermore, the EM intervention effectively reduced psychophysiological affective responses, including the skin conductance response and pupil size, to film scenes and subjective affective ratings of film-related intrusions. Together, bilateral EMs effectively reduce the perceptual representation and affective response of trauma-related memories. Further theoretical developments are needed to elucidate the mechanism of bilateral EMs in trauma treatment.

Facilitated extinction but impaired extinction recall by eye movement manipulation in humans - Indications for action mechanisms and the applicability of eye movement desensitization

Eye movement desensitization and reprocessing (EMDR) therapy utilizes the manipulation of eye movements to reduce affective distress during fear-exposure. Animal research recently suggested a potential neural mechanism underlying these effects, by which increased activity of the superior colliculus (SC), mediating visual attention, increases the inhibition of the basolateral amygdala (BLA), mediating defensive plasticity. We tested such mechanism in forty healthy humans using a multiple-day single-cue fear conditioning and extinction paradigm. The activity of the SC during extinction was experimentally manipulated by eye movements, as half of the participants executed saccadic eye movements (n = 20; major SC involvement), while the other half executed smooth eye pursuits (n = 20; minor SC involvement). Amygdala-mediated fear-potentiated startle responses and fear bradycardia, as well as threat expectancy was analyzed. Saccadic eye movements facilitated the extinction of fear bradycardia and fear-potentiated startle responses. Higher saccadic accuracy and range correlated with reduced fear-potentiated startle. However, during extinction recall, fear-potentiated startle and fear bradycardia resurged and partly reached levels obtained after fear acquisition. Threat expectancy was not affected by different eye movements and was not elevated during extinction recall. Within limitations, results support an inhibitory SC-BLA pathway in humans by which eye movements may reduce low-level defensive responding, but not threat expectancy. Yet, manipulating eye movements during extinction learning seems to impair extinction recall for behavioral and physiological defensive response indices. Thus, increasing SC activity might enhance initial efficacy of exposure treatment, but additional strategies seem necessary for sustained fear attenuation.

Effects of saccadic eye movements on episodic & semantic memory fluency in older and younger participants

Research has demonstrated that performing a sequence of saccadic horizontal eye movements prior to retrieval facilitates performance on tests of episodic memory. This has been observed in both laboratory tasks of retention and autobiographical memory. To date, the work has centred on performance in younger individuals. This paper extends previous investigations by examining the effects of saccadic eye movements in older persons. Autobiographical episodic and semantic memory fluency was assessed in younger (age range 18-35, mean = 22.50), and older (age range 55-87, mean = 70.35) participants following saccadic (vs. fixation control) manipulations. The main effects of eye movements and age were found for episodic autobiographical memory (greater fluency after eye movements and in younger participants). Semantic autobiographical memory showed a main effect of age (greater fluency in younger participants), whereas general semantic memory showed no effect of age or eye movement. These findings indicate that saccadic horizontal eye movements can enhance episodic personal memory in older individuals. This has implications as a technique to improve autobiographical recollection in the elderly and as an adjunct in reminiscence therapy.

Emerging Wearable Biosensor Technologies for Stress Monitoring and Their Real-World Applications

Wearable devices are being developed faster and applied more widely. Wearables have been used to monitor movement-related physiological indices, including heartbeat, movement, and other exercise metrics, for health purposes. People are also paying more attention to mental health issues, such as stress management. Wearable devices can be used to monitor emotional status and provide preliminary diagnoses and guided training functions. The nervous system responds to stress, which directly affects eye movements and sweat secretion. Therefore, the changes in brain potential, eye potential, and cortisol content in sweat could be used to interpret emotional changes, fatigue levels, and physiological and psychological stress. To better assess users, stress-sensing devices can be integrated with applications to improve cognitive function, attention, sports performance, learning ability, and stress release. These application-related wearables can be used in medical diagnosis and treatment, such as for attention-deficit hyperactivity disorder (ADHD), traumatic stress syndrome, and insomnia, thus facilitating precision medicine. However, many factors contribute to data errors and incorrect assessments, including the various wearable devices, sensor types, data reception methods, data processing accuracy and algorithms, application reliability and validity, and actual user actions. Therefore, in the future, medical platforms for wearable devices and applications should be developed, and product implementations should be evaluated clinically to confirm product accuracy and perform reliable research.

On the Effect of Bilateral Eye Movements on Memory Retrieval in Ageing and Dementia

It has been reported that performing bilateral eye movements for a short period can lead to an enhancement of memory retrieval and recall (termed the “saccade induced retrieval effect (SIRE)”). The source of this effect has been debated within the literature and the phenomenon has come under scrutiny as the robustness of the effect has recently been questioned. To date investigations of SIRE have largely been restricted to younger adult populations. Here, across two experiments, we assess the robustness and generalisability of the SIRE specifically in relation to disease and ageing. Experiment 1 employed a between subject’s design and presented younger and older participants with 36 words prior to completing one of three eye movement conditions (bilateral, antisaccade or a fixation eye movement). Participants then performed a word recognition task. Experiment 2 assessed the SIRE in individuals diagnosed with Alzheimer’s, Mild cognitive impairment and Parkinson’s by employing an online within subject’s design. Results showed no significant difference between groups in the number of words recognised based on eye movement condition. Neither experiment 1 or 2 replicated the SIRE effect therefore the findings from this study add to the growing number of studies that have failed to replicate the SIRE effect.

Memory and eye movement desensitization and reprocessing therapy: a potentially risky combination in the courtroom

Does Eye Movement and Desensitization and Reprocessing (EMDR) therapy affect the accuracy of memories? This recurrent issue in recent memory research bears relevance to expert witness work in the courtroom. In this review, we will argue that several crucial aspects of EMDR may be detrimental to memory. First, research has shown that eye movements undermine the quality and quantity of memory. Specifically, eye movements have been shown to decrease the vividness and emotionality of autobiographical experiences and amplify spontaneous false memory levels. Second, a sizeable proportion of EMDR practitioners endorse the controversial idea of repressed memories and discuss the topic of repressed memory in therapy. Third, in the Dutch EMDR protocol, patients are instructed to select the target image by using flawed metaphors of memory (e.g., memory works as a video). Such instructions may create demand characteristics to the effect that people over-interpret imagery during therapy as veridical memories. Collectively, the corpus of research suggests that several components of EMDR therapy (i.e., performing eye movements, therapist beliefs and therapeutic instructions) may undermine the accuracy of memory, which can be risky if patients, later on, serve as witnesses in legal proceedings.

Horizontal but not vertical saccades enhance memory retrieval: A meta-analysis and systematic review

Saccade-induced retrieval enhancement (SIRE) refers to the phenomenon that actively engaging in horizontal eye movements before recall enhances subsequent memory performance. This effect is thought to be the result of interhemispheric interactions stimulated by saccades. An alternative explanation is that saccades promote memory retrieval by improving top-down attention control. Thus, the mechanisms of SIRE are unclear, and the present meta-analysis quantitatively analysed the effect of saccades on memory performance and examined the mechanisms of SIRE. We searched "Web of Science," "PubMed," and "Springer" for peer-reviewed papers using the keywords "eye movements + memory" and "saccades + memory." Twenty-two papers were included in the final analysis. There was a significant facilitation of horizontal saccades on overall memory performance, with a pooled effect size (Cohen's d) of 0.45 (p < .001). However, the overall effect of vertical saccades was not significant (d = 0.1, p = .14). Moderation analysis showed that the handedness of participants was a significant moderator of SIRE, with strongly right-handed individuals benefitting more from horizontal saccades than non-strongly right-handed individuals (p < .01). Horizontal saccades improved memory performance, particularly for strongly right-handed individuals. These results support the interhemispheric interaction hypothesis.

Predicting interactions in handedness research: The role of integrated versus independent dual-processes

Over the past two decades, a new way of looking at handedness has emerged (see Prichard, E., Propper, R. E., & Christman, S. D. (2013). Degree of handedness, but not direction, is a systematic predictor of cognitive performance. Frontiers in Psychology, 4, 1-6), with an emphasis on degree (strong/consistent versus mixed/inconsistent) augmenting the traditional emphasis on direction (left versus right) of handedness. Much of this work has focused on main effects: e.g., inconsistent-handers show higher (or lower) performance than consistent-handers. However, many of these "main effects" are actually nested within higher order interactions: e.g., there are no handedness differences in a baseline/control condition, with handedness differences emerging in an experimental condition. Careful examination, though, of these interactions reveals an intriguing and predictable pattern: for integrated dual processes (e.g., episodic memory encoding versus retrieval), the interactions reflect larger effects in inconsistent-, relative to consistent-, handers. For independent, mutually exclusive dual processes (e.g., approach versus withdrawal), the interactions reflect larger effects in consistent-handers. It is argued that these patterns reflect the relative inability of (i) consistent-handers to integrate dual processes, and (ii) inconsistent-handers to keep independent dual processes separate. We also use this same theory to address higher order interactions involving changes in the experimental context as well as other individual difference factors, and make suggestions for future research.

EMDR in Cancer Patients: A Systematic Review

Background: Psychological distress is common among patients with cancer, with severe consequences on their quality of life. Anxiety and depression are the most common clinical presentation of psychological distress in cancer patients, but in some cases cancer may represent a traumatic event resulting in posttraumatic stress disorder (PTSD). Currently, Eye Movement Desensitization and Reprocessing (EMDR) therapy is considered an evidence-based treatment for PTSD, but recent studies also showed its effectiveness for anxiety and depression. The aim of the present systematic review is to summarize the current literature on the effect of EMDR on cancer-related psychological distress. Methods: A literature search was conducted for peer-reviewed articles about "EMDR" and "cancer patients" in the following electronic databases: PubMed, MEDLINE, Science Direct, Google Scholar, and Cochrane library. Results: Our search identified 7 studies in which EMDR was used with a total of 140 cancer patients. The psychiatric diagnosis was PTSD in 3 studies. Otherwise, the diagnosis concerned the anxious and depressive disorder spectrum. Overall, EMDR treatment schedules used were highly heterogeneous, with a different number of sessions (from 2 to 12) and a different duration of therapy (up to 4 months). However, across all studies analyzed EMDR therapy was judged to be adequate in reducing symptoms of psychological distress in this population. Conclusions: According to the results of our analysis, the level of evidence regarding EMDR efficacy in cancer patients is limited by the scarcity of studies and their low methodological quality. Although better quality research is needed, available data suggest that EMDR could be a promising treatment for psychological distress in patients with cancer.

Memory Effects of Manipulating Text Column Width: Eye-Movement Induced Attentional Processes Interfere With Prose Encoding Among Consistent Handers

Performing bilateral saccadic eye-movements has enhanced subsequent verbal recall among consistent handers (people who use their dominant hands for virtually all tasks) but not inconsistent handers (people who use their non-dominant hands for some tasks); but eye-movements prior to encoding have disrupted recall in consistent handers. We sought to better understand how this research might be applied to recalling written text presented in ways that differentially affected eye movements. We manipulated text column width in order to test whether induced eye movements and resultant right hemisphere activations would lead consistent handed (versus inconsistent handed) readers to experience encoding disruptions and poorer recall of the written passage. We presented participants, divided by handedness consistency and gender, with a story about a fictional island in which the lines of text were either ∼28 or ∼120 characters wide. We later asked participants to answer 20 questions about the story and measured their memory performance by both their percentage of correct answers and by their correct answers adjusted for a guessing tendency. We found a handedness by text width interaction. Consistent handers who read the story in a narrower column width showed poorer recall than both inconsistent handers and consistent handers who read the story in the wider text column. We suggest a chain of events such that text width altered eye-movements that, in turn, activated right hemisphere brain processes associated with orienting attention and attentional control, competing with consistent handers' encoding.

The electrophysiological underpinnings of variation in verbal working memory capacity

Working memory (WM) consists of short-term storage and executive components. We studied cortical oscillatory correlates of these two components in a large sample of 156 participants to assess separately the contribution of them to individual differences in WM. The participants were presented with WM tasks of above-average complexity. Some of the tasks required only storage in WM, others required storage and mental manipulations. Our data indicate a close relationship between frontal midline theta, central beta activity and the executive components of WM. The oscillatory counterparts of the executive components were associated with individual differences in verbal WM performance. In contrast, alpha activity was not related to the individual differences. The results demonstrate that executive components of WM, rather than short-term storage capacity, play the decisive role in individual WM capacity limits.

Increased functional homotopy of the prefrontal cortex is associated with corpus callosum degeneration and working memory decline

Functional homotopy reflects the link between spontaneous activity in a voxel and its counterpart in the opposite hemisphere. Alterations in homotopic functional connectivity (FC) are seen in normal aging, with highest and lowest homotopy being present in sensory-motor and higher-order regions, respectively. Homotopic FC relates to underlying structural connections, but its neurobiological underpinnings remain unclear. The genu of the corpus callosum joins symmetrical parts of the prefrontal cortex (PFC) and is susceptible to age-related degeneration, suggesting that PFC homotopic connectivity is linked to changes in white-matter integrity. We investigated homotopic connectivity changes and whether these were associated with white-matter integrity in 338 individuals. In addition, we examined whether PFC homotopic FC was related to changes in the genu over 10 years and working memory over 5 years. There were increases and decreases in functional homotopy, with the former being prevalent in subcortical and frontal regions. Increased PFC homotopic FC was partially driven by structural degeneration and negatively associated with working memory, suggesting that it reflects detrimental age-related changes.

Motor behavior-induced prefrontal cortex activation and episodic memory function

BACKGROUND

The objective of this paper was to evaluate the potential individual and combined effects of acute exercise coupled with bilateral interhemispheric activation on episodic memory function. Six experiments were conducted.

METHODS

Experiment 1 was a within-subject, counterbalanced experiment. Participants completed four visits, including 1) exercise and saccadic eye movements, 2) exercise only, 3) saccadic eye movements only, and 4) no exercise and no saccadic eye movements (control). A word-list memory assessment was employed, including a long-term (20-min delay) memory evaluation. In Experiment 2, we evaluated the effects of saccadic eye movements on prefrontal cortex oxygenation, a proxy for neuronal activity. Similarly, in our third experiment, we evaluated the effects of acute exercise on prefrontal cortex oxygenation. Thus, experiments 2 and 3 were employed to provide mechanistic insights from the results shown in experiment 1. Experiment 4 replicated Experiment 1, but instead of increasing prefrontal cortex activation via saccadic eye movements, we used a fist clenching protocol. Experiment 5 evaluated the effects of fist clenching on prefrontal cortex oxygenation.

RESULTS

Collectively, these 5 experimental studies showed that acute exercise (Experiment 1), saccadic eye movements (Experiment 1), and fist clenching (Experiment 4) enhanced memory function, and that acute exercise (Experiment 3), saccadic eye movements (Experiment 2) and fist clenching (Experiment 5) all increased prefrontal cortex oxygenation. Experiment 6 demonstrated that prefrontal cortex oxygenation was positively associated with episodic memory function.

CONCLUSION

These six experiments suggest that several behaviors, such as acute exercise, saccadic eye movements and fist clenching may improve memory function and may, potentially, do so via increases in prefrontal cortex oxygenation.

Re-evaluating whether bilateral eye movements influence memory retrieval

Several recent studies have reported enhanced memory when retrieval is preceded by repetitive horizontal eye movements, relative to vertical or no eye movements. The reported memory boost has been referred to as the Saccade-Induced Retrieval Enhancement (SIRE) effect. Across two experiments, memory performance was compared following repetitive horizontal or vertical eye movements, as well as following a control condition of no eye movements. In Experiment 1, we conceptually replicated Christman and colleagues’ seminal study, finding a statistically significant SIRE effect, albeit with weak Bayesian evidence. We therefore sought to conduct another close extension. In Experiment 2, horizontal and vertical eye movement conditions were manipulated separately, and sample size was increased. No evidence of a SIRE effect was found: Bayesian statistical analyses demonstrated significant evidence for a null effect. Taken together, these experiments suggest that the SIRE effect is inconsistent. The current experiments call into question the generalizability of the SIRE effect and suggest that its presence is very sensitive to experimental design. Future work should further assess the robustness of the effect before exploring related theories or underlying mechanisms.

Saccade-induced retrieval enhancement and the recovery of perceptual item-specific information

Saccade-induced retrieval enhancement (SIRE) effects refer to the finding that memory can be enhanced when a short period of saccadic eye movements takes place prior to retrieval. Previous published work testifies to this eye movement advantage, but no work has yet examined if SIRE effects can be found when retrieval demands are high as a result of testing non-studied memoranda that are identical in name/conceptual codes, similar in perceptual features, but differ in terms of perceptual-item-specific information. The results indicate SIRE effects can be found under such conditions and are independent of encoding orientation (intentional vs. incidental). More particularly, SIRE effects manifested themselves in terms of the retrieval of item-specific detail and recollection (vs. familiarity). In terms of the latter, recollection but not familiarity was enhanced by eye movements. These findings are considered in the context of extant theories of SIRE and related research.

Fear not: recent advances in understanding the neural basis of fear memories and implications for treatment development

Fear is a highly adaptive emotion that has evolved to promote survival and reproductive fitness. However, maladaptive expression of fear can lead to debilitating stressor-related and anxiety disorders such as post-traumatic stress disorder. Although the neural basis of fear has been extensively researched for several decades, recent technological advances in pharmacogenetics and optogenetics have allowed greater resolution in understanding the neural circuits that underlie fear. Alongside conceptual advances in the understanding of fear memory, this increased knowledge has clarified mechanisms for some currently available therapies for post-traumatic stress disorder and has identified new potential treatment targets.

Stress Management Intervention to Prevent Post-Intensive Care Syndrome-Family in Patients' Spouses

BACKGROUND

Post-intensive care syndrome-family (PICS-F) refers to acute and chronic psychological effects of critical care on family members of patients in intensive care units (ICUs). Evidence suggests that increased distress during the ICU stay increases risk of PICS-F. Sensation Awareness Focused Training (SĀF-T) is a new, promising stress management intervention, but the feasibility of such training during the ICU stay for family caregivers who are acting as the surrogate decision-maker for patients who are undergoing mechanical ventilation is unknown.

OBJECTIVES

To assess feasibility and acceptability of SĀF-T to inform a future larger randomized controlled trial.

METHODS

This randomized controlled trial of SĀF-T (n = 5) versus a control (n = 5) group was conducted at a level 1 trauma center. Participants assigned to SĀF-T completed 1 session daily for 3 days. Measures included enrollment rate, data completion rate, acceptability of SĀF-T, and symptoms of PICS-F. Scales used included Perceived Stress, Hospital Anxiety and Depression, Impact of Event, and National Institutes of Health Toolbox Emotion Battery.

RESULTS

Mean age was 58 (SD, 12) years; 70% of participants were female. Predetermined feasibility criteria were met in enrollment rate (67%), outcome measures completion rate (> 90%), and SĀF-T acceptability (100% of doses completed during the ICU stay) without adverse events. Stress scores after SĀF-T were significantly lower than scores before SĀF-T (z = -3.5, P = .01).

CONCLUSIONS

SĀF-T intervention during the ICU stay is feasible, acceptable, and may improve family caregivers' post-ICU outcomes. Larger clinical trial to assess the effectiveness of SĀF-T in preventing PICS-F seem warranted.

The Predictive Processing Model of EMDR

Eye Movement Desensitization and Reprocessing Therapy (EMDR) is an effective treatment for Post-traumatic Stress Disorder (PTSD). The Adaptive Information Processing Model (AIP) guides the development and practice of EMDR. The AIP postulates inadequately processed memory as the foundation of PTSD pathology. Predictive Processing postulates that the primary function of the brain is prediction that serves to anticipate the next moment of experience in order to resist the dissipative force of entropy thus facilitating continued survival. Memory is the primary substrate of prediction, and is optimized by an ongoing process of precision weighted prediction error minimization that refines prediction by updating the memories on which it is based. The Predictive Processing model of EMDR postulates that EMDR facilitates the predictive processing of traumatic memory by overcoming the bias against exploration and evidence accumulation. The EMDR protocol brings the traumatic memory into an active state of re-experiencing. Defensive responding and/or low sensory precision preclude evidence accumulation to test the predictions of the traumatic memory in the present. Sets of therapist guided eye movements repeatedly challenge the bias against evidence accumulation and compel sensory sampling of the benign present. Eye movements reset the theta rhythm organizing the flow of information through the brain, facilitating the deployment of both overt and covert attention, and the mnemonic search for associations. Sampling of sensation does not support the predictions of the traumatic memory resulting in prediction error that the brain then attempts to minimize. The net result is a restoration of the integrity of the rhythmic deployment of attention, a recalibration of sensory precision, and the updating (reconsolidation) of the traumatic memory. Thus one prediction of the model is a decrease in Attention Bias Variability, a core dysfunction in PTSD, following successful treatment with EMDR.

Looking up improves performance in verbal tasks

Earlier research suggested that gaze direction has an impact on cognitive processing. It is likely that horizontal gaze direction increases activation in specific areas of the contralateral cerebral hemisphere. Consistent with the lateralization of memory functions, we previously showed that shifting gaze to the left improves visuo-spatial short-term memory. In the current study, we investigated the effect of unilateral gaze on verbal processing. We expected better performance with gaze directed to the right because language is lateralized in the left hemisphere. Also, an advantage of gaze directed upward was expected because local processing and object recognition are facilitated in the upper visual field. Observers directed their gaze at one of the corners of the computer screen while they performed lexical decision, grammatical gender and semantic discrimination tasks. Contrary to expectations, we did not observe performance differences between gaze directed to the left or right, which is consistent with the inconsistent literature on horizontal asymmetries with verbal tasks. However, RTs were shorter when observers looked at words in the upper compared to the lower part of the screen, suggesting that looking upwards enhances verbal processing.

Effects of gaze stability exercises on cognitive function, dynamic postural ability, balance confidence, and subjective health status in old people with mild cognitive impairment

The purpose of this study was to determine whether gaze stability exercises would result in improvements of cognitive function, balance ability and subjective health status in old people with and without mild cognitive impairment (MCI). Old people with MCI (n=9) and healthy old people (n=9) performed gaze stability exercises for 4 weeks. Pre and post Montreal Cognitive Assessment (MoCA) for cognitive function, Timed Up and Go test for dynamic postural ability, Activities-Specific Balance Confidence for balance confidence and subjective health status were measured in both groups. After participating in gaze stability exercises, all outcome measures were significantly improved in MCI group and normal group also improved significantly in all outcome measures with the exception of balance confidence. In addition, there were significant differences in cognitive function and balance confidence between the two groups, and more improvements in MCI group. These results provide evidence that gaze stability exercises is beneficial to improve cognitive function as well as balance ability which affected on quality of life in old people with and without MCI.

Should we pay attention to eye movements? The impact of bilateral eye movements on behavioral and neural responses during the Attention Network Test

Bilateral eye movements (EMs) have been associated with enhancements in episodic memory and creativity. We explored the influence of EMs on behavior and event related potential (ERP) responses during the Attention Network Test (ANT). Participants completed ANT trials after bilateral EMs or a center-fixation control manipulation. We examined condition (EM, control) and handedness (consistent, inconsistent) differences for overall task performance, as well as alerting, orienting, and executive attention networks. Behaviorally, there was a trend for inconsistent-handed participants to display faster RTs across cue types, and greater accuracy for no cue, double, and center cue trials when compared to consistent handers, yet consistent handers garnered greater improvements in behavior following altering and orienting cues than inconsistent handers. Although there were no behavioral differences between EM and control conditions, target-locked N100 and P200 ERPs were weaker in the EM than control condition for all cue types, except spatial cues for which there were no differences between groups. Because stronger N100 and P200 responses have been linked to increased selective attention, we speculate that ERP differences between EM and control conditions, in the absence of behavioral differences, may indicate that participants exposed to EMs required less selective attention to successfully complete the task.

Saccades and handedness interact to affect scene memory

Repetitive saccades benefit memory when executed before retrieval, with greatest effects for episodic memory in consistent-handers. Questions remain including how saccades affect scene memory, an important visual component of episodic memory. The present study tested how repetitive saccades affect working and recognition memory for novel scenes. Handedness direction (left–right) and degree (strong/consistent vs. mixed/inconsistent) was measured by raw and absolute laterality quotients respectively from an 8-question handedness inventory completed by 111 adults. Each then performed either 30 s of repetitive horizontal saccades or fixation before or after tasks of scene working memory and scene recognition. Regression with criterion variables of overall percent correct accuracy and d-prime sensitivity showed that when saccades were made before working memory, there was better overall accuracy as a function of increased direction but not degree of handedness. Subjects who made saccades before working memory also performed worse during subsequent recognition memory, while subjects who fixated or made saccades after the working memory task performed better. Saccades made before recognition resulted in recognition accuracy that was better (Cohen’s d = 0.3729), but not significantly different from fixation before recognition. The results demonstrate saccades and handedness interact to affect scene memory with larger effects on encoding than recognition. Saccades before scene encoding in working memory are detrimental to short- and long-term memory, especially for those who are not consistently right-handed, while saccade execution before scene recognition does not appear to benefit recognition accuracy. The findings are discussed with respect to theories of interhemispheric interaction and control of visuospatial attention.

Stochastic resonance as a proposed neurobiological model for Eye Movement Desensitization and Reprocessing (EMDR) therapy

EMDR therapy is recommended in several guidelines in the International field of psychological trauma. The dual attention stimuli/alternating bilateral stimulation (DAS/ABS) element of EMDR therapy has no proposed mechanism of action agreed upon, which explains the rapid shifts in cognitions and dysfunctional traumatic memory networks that are central to its observable efficacy. This paper discusses an innate, biological mechanism found in biological systems, including the human nervous system that may explain the efficacy of DAS/ABS. This mechanism is stochastic resonance (SR). SR is observed to make unintelligible, subthreshold signals intelligible and facilitates signal transmission. It provides a potential mechanism for discrimination and the selective focusing of attention, which are important factors in effective psychotherapy for the psychologically traumatised individual. The body/mind complex aims to achieve the functional encoding of memories in the neocortex and a key structural crossroads in this process is the thalamus. Activity in the thalamus is decreased in Post-Traumatic Stress Disorder (PTSD) compared to non-PTSD patients and a form of 'gating' is known to occur at the thalamic level. This 'gating' is adaptive and it is postulated to protect the higher neocortical systems in times of trauma. Although the model is initially somewhat counterintuitive, Stochastic Resonance; a form of random 'noise', can be considered 'helpful randomness' and when present in the thalamus SR can help filter and control sensitivity to incoming signals; helping to discriminate what is communicated. Naturally occurring SR is normally present as a result of descending cortico-thalamic activity, but appears attenuated as a result of exposure to trauma. The view of 'noise' in the current era of cell phones and High Definition is generally negative with science going to significant lengths to clean up signals: i.e. removing noise from them. We do not want white noise in our music or during our cell phone calls. However, some researchers invite us to consider that not all noise is bad and the downward cortico-thalamic 'noise' is an example of this category of 'helpful noise'. This paper will discuss the potential role of SR, as the mechanism by which DAS/ABS generates a random (stochastic) signal, facilitating a return to functional memory processing, where there is a lack of naturally occurring noise from the descending cortico-thalamic connections because of exposure to trauma. Modelling the mechanism as SR will facilitate further study into EMDR therapy and this will hopefully encourage perspicacity, where there has previously been derision.

How Does Eye Movement Desensitization and Reprocessing Therapy Work? A Systematic Review on Suggested Mechanisms of Action

Background: Eye movement desensitization and reprocessing [EMDR] is an innovative, evidence-based and effective psychotherapy for post-traumatic stress disorder [PTSD]. As with other psychotherapies, the effectiveness of EMDR contrasts with a limited knowledge of its underlying mechanism of action. In its relatively short life as a therapeutic option, EMDR has not been without controversy, in particular regarding the role of the bilateral stimulation as an active component of the therapy. The high prevalence of EMDR in clinical practice and the dramatic increase in EMDR research in recent years, with more than 26 randomized controlled trials published to date, highlight the need for a better understanding of its mechanism of action.

Methods: We conducted a thorough systematic search of studies published until January 2018, using PubMed, ScienceDirect, Web of Knowledge and Scopus databases that examined the mechanism of action of EMDR or provided conclusions within the framework of current theoretical models of EMDR functioning.

Results: Eighty-seven studies were selected for review and classified into three overarching models; (i) psychological models (ii) psychophysiological models and (iii) neurobiological models. The evidence available from each study was analyzed and discussed. Results demonstrated a reasonable empirical support for the working memory hypothesis and for the physiological changes associated with successful EMDR therapy. Recently, more sophisticated structural and functional neuroimaging studies using high resolution structural and temporal techniques are starting to provide preliminary evidence into the neuronal correlates before, during and after EMDR therapy.

Discussion: Despite the increasing number of studies that published in recent years, the research into the mechanisms underlying EMDR therapy is still in its infancy. Studies in well-defined clinical and non-clinical populations, larger sample sizes and tighter methodological control are further needed in order to establish firm conclusions.

Eye movement desensitization and reprocessing as a treatment for PTSD: current neurobiological theories and a new hypothesis

Eye movement desensitization and reprocessing (EMDR), a form of psychotherapy for individuals with post-traumatic stress disorder (PTSD), has long been a controversial topic, hampered in part by a lack of understanding of the neural mechanisms that contribute to its remedial effect. Here, we review current theories describing EMDR's potential neurobiological mechanisms of action involving working memory, interhemispheric communication, de-arousal, and memory reconsolidation. We then discuss recent studies describing the temporal and spatial aspects of smooth pursuit and predictive saccades, which resemble those made during EMDR, and their neural correlates within the default mode network (DMN) and cerebellum. We hypothesize that if the production of bilateral predictive eye movements is supportive of DMN and cerebellum activation, then therapies that shift the brain towards this state correspondingly would benefit the processes regulated by these structures (i.e., memory retrieval, relaxation, and associative learning), all of which are essential components for PTSD recovery. We propose that the timing of sensory stimulation may be relevant to treatment effect and could be adapted across different patients depending on their baseline saccade metrics. Empirical data in support of this model are reviewed and experimental predictions are discussed.

Changes in brain connectivity following exposure to bilateral eye movements

The present research assessed how engaging in bilateral eye movements influences brain activity. Participants had their resting-state brain activity recorded with electroencephalography (EEG) before and after they performed 30 s of bilateral eye movements or a center-control manipulation. We assessed differences in change scores for absolute power and coherence between the eye-movement and center-control conditions. A main effect for handedness was present for EEG power in the theta and beta frequency bands, with inconsistent-handed participants displaying a greater increase than consistent-handed participants in both frequency bands. For theta, the increase in power for inconsistent handers was specific to participants in the bilateral eye-movement condition, whose increase in theta power exceeded the increase in theta power for consistent-handed participants regardless of condition. In contrast, for coherence, a main effect for condition was present for the delta frequency band, with participants in the control condition exhibiting a significant drop in posterior delta coherence pre to post. We suggest that the maintenance of posterior delta coherence over time may be an important factor in sustaining attention. Further, the malleability of EEG power for inconsistent-handed participants reveals the importance of individual-differences variables in the potential for behavioral manipulations to change brain activity.

Integrating neurobiology of emotion regulation and trauma therapy: reflections on EMDR therapy

Emotion dysregulation is a frequent feature in trauma-related disorders. Different kinds of emotion dysregulation seem to be linked to particular psychiatric conditions, and there is growing evidence of the association between neurobiological correlates and those dysregulation patterns. Nevertheless, many of the recent findings from the field of the neurobiology have not been translated into clinical practice and are insufficiently contemplated in trauma-oriented therapies. The aim of this article is to review recent developments in the field of emotion regulation connecting these issue with the practical implementation of psychotherapeutic procedures. The evaluation of emotion dysregulation patterns can guide decision making during the therapy independently to the approach, but there are some findings that can be especially useful for some concrete modalities of therapy. In this article we will focus our discussion on how emotion dysregulation may influence eye movement desensitization and reprocessing (EMDR) treatment in trauma-related disorders. EMDR is a well-defined and protocol-based intervention, with a strong empirical support for post-traumatic stress disorder (PTSD). We describe how different patterns of emotion dysregulation may influence EMDR treatment and procedures, and also how the application of EMDR beyond non-dissociative PTSD should take into account the predominant emotion-regulation strategies in specific posttraumatic disorders.

Effects of handedness consistency and saccade execution on eyewitness memory in cued- and free-recall procedures

Identifying characteristics that distinguish between people with relatively good versus poor episodic memory is an important goal of eyewitness-memory research, as is identifying activities that can improve people's ability to retrieve episodic memories. Consistency of hand preference is a trait associated with the quality of people's episodic memory and repetitive saccade execution is an activity known to improve people's ability to retrieve episodic memories. These factors were examined in relation to cued and free recall of a staged criminal event. Individuals with inconsistent hand preference (versus consistent) remembered more on a cued-recall test and also freely recalled a larger amount of victim information. Repetitive saccade execution did not increase cued recall but did increase free recall of victim information. Theoretical implications are discussed, as is potential practical significance, with an emphasis on the size of the observed effects.

Effects of Saccade Induced Retrieval Enhancement on conceptual and perceptual tests of explicit & implicit memory

The effects of saccadic horizontal (bilateral) eye movements upon tests of both conceptual and perceptual forms of explicit and implicit memory were investigated. Participants studied a list of words and were then assigned to one of four test conditions: conceptual explicit, conceptual implicit, perceptual explicit, or perceptual implicit. Conceptual tests comprised category labels with either explicit instructions to recall corresponding examples from the study phase (category-cued recall), or implicit instructions to generate any corresponding examples that spontaneously came to mind (category-exemplar generation). Perceptual tests comprised of word-fragments with either explicit instructions to complete these with study items (word-fragment-cued recall), or implicit instructions to complete each fragment with the first word that simply 'popped to mind' (word-fragment completion). Just prior to retrieval, participants were required to engage in 30 s of bilateral vs. no eye movements. Results revealed that saccadic horizontal eye movements enhanced performance in only the conceptual explicit condition, indicating that Saccade-Induced Retrieval Enhancement is a joint function of conceptual and explicit retrieval mechanisms. Findings are discussed from both a cognitive and neuropsychological perspective, in terms of their potential functional and neural underpinnings.

The effects of varying levels of hemispheric activation on episodic memory

Bilateral saccadic eye movements enhance episodic memory retrieval; however, this usually only occurs for consistent-handed, not inconsistent-handed, individuals. It was hypothesized that inconsistent-handers begin closer to the peak of a Yerkes-Dodson-type inverted-U curve and increasing activation pushes them along the curve eventually decreasing performance, while consistent-handers start at a lower baseline and therefore increasing activation increases their performance. The current study tested this hypothesis by using hand clenching (grip strength) to increase activation at 5 different levels for both consistent- and inconsistent-handers. A total of 316 participants were presented with a list of 36 words after which they squeezed a hand dynamometer to induce cortical activation, and then recalled as many of the words as they could. Results showed that, as predicted, both inconsistent- and consistent-handers demonstrated an inverted-U pattern of memory performance as the strength of squeeze increased with inconsistent-handers peaking at a lower level of grip strength than consistent-handers. These results may help explain past findings, not only with episodic memory but also a variety of other cognitive tasks. They may also have interesting theoretical and real-world implications, which are discussed.

Degrading emotional memories induced by a virtual reality paradigm

BACKGROUND AND OBJECTIVES

In Eye Movement and Desensitization and Reprocessing (EMDR) therapy, a dual-task approach is used: patients make horizontal eye movements while they recall aversive memories. Studies showed that this reduces memory vividness and/or emotionality. A strong explanation is provided by working memory theory, which suggests that other taxing dual-tasks are also effective. Experiment 1 tested whether a visuospatial task which was carried out while participants were blindfolded taxes working memory. Experiment 2 tested whether this task degrades negative memories induced by a virtual reality (VR) paradigm.

METHODS

In experiment 1, participants responded to auditory cues with or without simultaneously carrying out the visuospatial task. In experiment 2, participants recalled negative memories induced by a VR paradigm. The experimental group simultaneously carried out the visuospatial task, and a control group merely recalled the memories. Changes in self-rated memory vividness and emotionality were measured.

RESULTS

The slowing down of reaction times due to the visuospatial task indicated that its cognitive load was greater than the load of the eye movements task in previous studies. The task also led to reductions in emotionality (but not vividness) of memories induced by the VR paradigm.

LIMITATIONS

Weaknesses are that only males were tested in experiment 1, and the effectiveness of the VR fear/trauma induction was not assessed with ratings of mood or intrusions in experiment 2.

CONCLUSIONS

The results suggest that the visuospatial task may be applicable in clinical settings, and the VR paradigm may provide a useful method of inducing negative memories.

Repairing Failures in Bonding Through EMDR

Maternal-infant bonding is an intense emotional tie between mother and infant that often begins during pregnancy and continues after birth. Prolonged physical separation from one’s infant or traumatic interference can sometimes impede this process, leading to a lack of bonding. Whereas many medical procedures and illnesses can cause mother and child to become separated immediately after birth and affect bonding, other causes of emotional separation may be somewhat more difficult to identify. Nevertheless, maternal trauma has been identified as one such form of emotional separation that can interfere with bonding. This article illustrates the application of Eye Movement Desensitization and Reprocessing (EMDR) for addressing bonding difficulties related to trauma issues. EMDR is an integrative psychotherapy that uses a standardized eight-phase approach to treatment and is a well-accepted treatment for trauma. Although more research is needed, this case suggests that EMDR may be an appropriate and efficient treatment for bonding difficulties

EMDR in the Treatment of Borderline Personality Disorder

Individuals diagnosed with borderline personality disorder (BPD) usually experience significant impairment in their ability to function. Impulsivity, affect instability, interpersonal difficulties, and identity problems are hallmark features of this disorder, frequently leading to suicidal and parasuicidal behaviors. Although BPD has traditionally been considered chronic and enduring, recent research has indicated that it can remit over time and that psychotherapy can accelerate this process. The etiology of BPD has been associated with childhood abuse and inadequate attachment. Given the significance of childhood abuse and trauma, eye movement desensitization and reprocessing (EMDR), a recognized trauma therapy, may be a reasonable treatment option for BPD. The positive effects noted in the following case illustrate EMDR’s utility in the treatment of BPD and indicate that further controlled studies are warranted.

25 years of Eye Movement Desensitization and Reprocessing (EMDR): The EMDR therapy protocol, hypotheses of its mechanism of action and a systematic review of its efficacy in the treatment of post-traumatic stress disorder

Eye movement desensitization and reprocessing (EMDR) is a relatively new psychotherapy that has gradually gained popularity for the treatment of post-traumatic stress disorder. In the present work, the standardised EMDR protocol is introduced, along with current hypotheses of its mechanism of action, as well as a critical review of the available literature on its clinical effectiveness in adult post-traumatic stress disorder. A systematic review of the published literature was performed using PubMed and PsycINFO databases with the keywords «eye movement desensitization and reprocessing» and «post-traumatic stress disorder» and its abbreviations «EMDR» and «PTSD». Fifteen randomised controlled trials of good methodological quality were selected. These studies compared EMDR with unspecific interventions, waiting lists, or specific therapies. Overall, the results of these studies suggest that EMDR is a useful, evidence-based tool for the treatment of post-traumatic stress disorder, in line with recent recommendations from different international health organisations.

Eye Movements Matter, But Why? Psychophysiological Correlates of EMDR Therapy to Treat Trauma in Timor-Leste

This preliminary study examined the physiological correlates of eye movement desensitization and reprocessing (EMDR) therapy when effectively used to treat trauma symptoms in a postconflict, developing nation, Timor-Leste. Participants were 20 Timorese adults with posttraumatic stress disorder (PTSD) symptoms treated with EMDR therapy. PTSD, depression, and anxiety decreased significantly after an average of 4.15 (SD = 2.06) sessions. Continuous measures of heart rate, skin conductance, and respiration were collected during the first and last desensitization sessions. Physiological activity decreased in EMDR desensitization sessions, and eye movement sets were associated with an immediate significant decrease in heart rate and an increase in skin conductance, consistent with an orienting response. This response habituated within and across eye movement sets. These findings suggest that effective EMDR therapy is associated with de-arousal within sessions and that eye movement sets are associated with distinct physiological changes that may aid memory processing. The findings offer insight into the working mechanisms of EMDR when used to treat PTSD symptoms in a real-world, cross-cultural, postwar/conflict setting.