User:Organizedchaos39/Dual consciousness

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* History of Alien Hand Syndrome was added by K. Ayer. Justification: Reports of AHS inspired the Dual Consciousness theory and the original section did not provide much information. The sentence about switching attention was also added.

Alien hand syndrome
Main article: Alien Hand Syndrome

Alien hand syndrome, sometimes used synonymously with anarchic hand is a neurological disorder in which the afflicted person's hand appears to take on a mind of its own. Alien hand syndrome has been documented in some split brain patients.

History
The first instance of Alien Hand Syndrome was reported in 1908 by Kurt Goldstein. This incident occurred to a woman in her 50s whose left hand grabbed her throat without her making the effort to do so. She was able to remove her hand, but it took a great deal of effort to do so. Upon her passing, an autopsy was performed which concluded that the event may have been caused by several strokes in her right hemisphere and corpus callosum. In the 1940s, reports surfaced of patients who had undergone corpus callosotomies that were experiencing uncontrollable hand movements following surgery. In these instances, the actions of one’s left hand conflicted with the actions of one’s right hand. The initial diagnosis for these experiences was “diagnostic dyspraxia”.

There are three main types of AHS. The first is the frontal variant, which is characterized by the nondominant hand grabbing items and manipulating objects. The second is the callosal variant, which is the most common form of AHS, is characterized by the uncontrollable and conflicting movement of a right-handed patient’s left hand. Callosal AHS often occurs alongside other symptoms of callosal damage such as alexia, the diminished or absent ability to comprehend written language, and visual anomia, the inability to name objects seen in the right vision field. The third type is the posterior variant. This type of AHS is characterized by the affected hand rising in the air and making non purposeful movements.

Symptoms
The classic sign of Alien Hand Syndrome is that the affected person cannot control one of their hands. For example, if a split-brain patient with Alien Hand Syndrome is asked to pick up a glass with their right hand, as the right hand moves over to the glass, the left hand will interfere with the action, thwarting the right hand's task. The interference from the left hand is completely out of the control of the patient and is not being done "on purpose". Affected patients at times cannot control the movements of their hands. Switching one's attention from one task to another can also lessen the amount of control that they can allocate to their affected hand. Another example included patients unbuttoning a shirt with one hand, and the other hand simultaneously re-buttoning the shirt (although some reported feeling normal after their surgery).

Relationship to dual consciousness
When scientists first started observing the alien hand syndrome in split-brain patients, they began to question the nature of consciousness and began to theorize that perhaps when the corpus callosum is cut, consciousness also is split into two separate entities. This development added to the general appeal of split-brain research.