EMDR Mechanism

The theory underlying EMDR treatment is that it works by helping the sufferer process distressing memories more fully which reduces the distress. EMDR is based on a theoretical information processing model which posits that symptoms arise when events are inadequately processed, and can be eradicated when the memory is fully processed. It is an integrative therapy, synthesizing elements of many traditional psychological orientations, such as psychodynamic, cognitive behavioral, experiential, physiological, and interpersonal therapies.[6]

EMDR's most unique aspect is an unusual component of bilateral stimulation of the brain, such as eye movement, bilateral sound, or bilateral tactile stimulation coupled with cognitions, visualized images and body sensation. EMDR also utilizes dual attention awareness to allow the individual to vacillate between the traumatic material and the safety of the present moment. This prevents retraumatization from exposure to the disturbing memory. As EMDR is an integrative therapy which combines elements of cognitive behavioral and psychodynamic therapies to desensitize traumatic memories, some individuals have criticized EMDR and consider the use of eye movement to be an unnecessary component of treatment.[7][8] However, recent studies have examined the effects of eye movement and have found that eye movement in EMDR decreases the vividness and/or negative emotions associated with autobiographical memories,[9][10][11][12] enhance the retrieval of episodic memories,[13] increase cognitive flexibility,[14] and correlate with decreases in heart rate, skin conductance, and an increased finger temperature.[15][16] These physiological changes associated with EMDR are consistent with earlier research on physiological changes associated with EMDR.[17] Also recent studies that have removed eye movement from the method have found the procedure less effective.[18]

There is no definitive explanation as to how EMDR works. There is some empirical support for three explanations regarding how an external stimulus such as eye movement can facilitate the processing of traumatic memories.

The first hypothesis views PTSD as a failure by the individual to process episodic memory;[19][20] the bilateral eye movement involved in EMDR facilitate interaction between the brain's hemispheres, which then improves the processing of trauma-related memories. This hypothesis is supported by a study that tested the effects of eye movement on the ability to retrieve episodic memory. The study found better recall following a horizontal eye movement task compared to that following no eye movement or a vertical eye movement task.[21]

A second hypothesis suggests that eye movement facilitates processing of trauma memories by activating a neurobiological state similar to REM sleep wherein associative links to episodic memories are formed and these memories are then integrated into general semantic networks. Stickgold proposed that PTSD occurs when an event is sufficiently arousing to prevent its transfer from encoding from an episodic memory to a semantic memory.[20] As a result of high arousal levels, associations between the traumatic event and other related events fail to develop. He argues that the attentional redirecting in EMDR induces a neurobiological state similar to REM sleep. He then reviews the research that suggests that REM sleep enhances processing of episodic memory through the preferential activation of weak associative and semantic links. Thus in EMDR trauma-related information that is closely associated with a target event is weakened and ancillary information loosely related to the event is strengthened, allowing the integration of trauma-related material with other loosely associated events in the person's life. Support for this argument comes from a study that found that, compared to eye fixation, eye movement promoted attentional flexibility and increased preparedness to process metaphorical material.[22]

A third hypothesis links the eye movement in EMDR with the orienting response.[23] MacCulloch and Feldman argued that eye movement triggers the investigation component of the orienting response, which can either produce avoidance behaviour or inhibit avoidance responses. Inhibiting avoidance behaviour includes reducing both negative somatic responses and cognitive changes that would allow fresh investigatory behaviour to commence. MacCulloch and Feldman proposed that initially when danger is identified there is a negative affect response. However a second part of the orienting response is to scan for further danger, and this investigatory reflex seems to accompany a positive physical response. In the authors' opinion, eye movement induces this investigatory reflex and produces a relaxation response. A relaxation response was, in fact, found in a study that investigated the autonomic responses of participants when they were engaged in an eye movement task as part of EMDR treatment[24] and when participants focused on negative memories while engaging in eye movement [23]. However there is not a differential effect of eye movement on a relaxation response when participants focused on positive memories.[10] This supports the hypothesis that eye movement is an orienting response mechanism rather than a simple relaxation mechanism. In addition, recent research that has examined the physiological correlates of eye movement in EMDR has found that a clear orienting response pattern of psycho-physiological de-arousal occurs when eye movement begins, and this de-arousal is characteristic of the physiological changes that occur when an orienting response is elicited.[25]

Further data consistent with the orienting response hypothesis was the finding that EMDR treatment was associated with increased left pre-frontal hemisphere activation.[26][27] Investigatory and approach behavior has been shown to be associated with the anterior left hemisphere regions.[28]

Source: Wikipedia