Dissociation, as a concept that has been developed over time, is any of a wide array of experiences, ranging from a mild emotional detachment from the immediate surroundings, to a more severe disconnection from physical and emotional experiences. The major characteristic of all dissociative phenomena involves a detachment from reality, rather than a loss of reality as in psychosis.The phenomena are diagnosable under the DSM-5 as a group of disorders as well as a symptom of other disorders through various diagnostic tools. Its cause is believed to be related to neurobiological mechanisms, trauma, anxiety, and psychoactive drugs. Research has further related it to suggestibility and hypnosis, and it is inversely related to mindfulness, which is a potential treatment. History
French philosopher and psychologist Pierre Janet (1859–1947) is considered to be the author of the concept of dissociation. Contrary to some conceptions of dissociation, Janet did not believe that dissociation was a psychological defense.Psychological defense mechanisms belong to Sigmund Freuds theory of psychoanalysis, not to Janetian psychology. Janet claimed that dissociation occurred only in persons who had a constitutional weakness of mental functioning that led to hysteria when they were stressed. Although it is true that many of Janets case histories described traumatic experiences, he never considered dissociation to be a defense against those experiences. Quite the opposite: Janet insisted that dissociation was a mental or cognitive deficit.
Deep brain stimulation
Deep brain stimulation (DBS) has been found to be an effective and safe treatment for myoclonus dystonia patients, whose severe and debilitating symptoms are resistant to drug treatments. Electrical stimulation within the brain is a common treatment for many movement disorders because of the ability to excite or inhibit neurons within the brain. Deep brain stimulation patients have electrodes inserted into the brain and then an electrical signal is sent from an external source to elicit a response. The frequency and intensity of this signal can be changed to monitor the effects on neuronal activity using voltage recordings or neuroimaging, like functional MRIs. By re-positioning the electrodes in different areas or changing the size or timing of the stimulus, varying effects can be seen on the patient depending on the origin of the disorder.In one study, five patients with genetically determined epsilon sarcoglycan protein deficiency  underwent deep brain stimulation of the internal pallidum. Each patients movement and disability symptoms were assessed before and after treatment using the Burke-Fahn-Marsden Dystonia Rating Scale and the Unified Myoclonus Rating Scale. Upon completion of the surgery, both the myoclonus and dystonia symptoms of the disorder had decreased by 70%, with no report of unfavorable side effects. Therefore, deep brain stimulation has been shown to effectively improve both myoclonus and dystonia, unlike many drug treatments which may improve one or the other.Other studies examined the effects of DBS to both the ventrointermediate nucleus of the thalamus, Vim, and the globus pallidus interna, GPi.