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Alien hand syndrome (AHS) is a rare neurological disorder that causes hand movement without the person being aware of what is happening or having control over the action. The afflicted person may sometimes reach for objects and manipulate them without wanting to do so, even to the point of having to use the healthy hand to restrain the alien hand. Alien hand syndrome is best documented in cases where a person has had the two hemispheres of their brain surgically separated, a procedure sometimes used to relieve the symptoms of extreme cases of epilepsy. It also occurs in some cases after brain surgery, stroke, infection, tumor, aneurysm and specific degenerative brain conditions such as Alzheimer's disease and Creutzfeldt–Jakob disease. Other areas of the brain that are associated with alien hand syndrome are the frontal, occipital and parietal lobes. The first known case described in the medical literature appeared in a detailed case report published in German in 1908 by the preeminent German neuro-psychiatrist, Kurt Goldstein. In this paper, Goldstein described a right-handed woman who had suffered a stroke affecting her left side from which she had partially recovered by the time she was seen. However, her left arm seemed as though it belonged to another person and performed actions that appeared to occur independent of her will. The patient complained of a feeling of "strangeness" in relationship to the goal-directed movements of the left hand and insisted that "someone else" was moving the left hand, and that she was not moving it herself. Goldstein reported that, as a result of this report, "she was regarded at first as a paranoiac." When the left hand grasped an object, she could not voluntarily release it. The somatic sensibility of the left side was reported to be impaired, especially with aspects of sensation having to do with the orienting of the limb. Some spontaneous movements were noted to occur involving the left hand, such as wiping the face or rubbing the eyes; but these were relatively infrequent. Only with significant effort was she able to perform simple movements with the left arm in response to spoken command, but these movements were performed slowly and often incompletely even if these same movements had been involuntarily performed with relative ease before while in the abnormal 'alien' control mode. Based on these remarkable observations, Goldstein developed a "doctrine of motor apraxia" in which he discussed the process involved in the generation of voluntary action and interpreted these findings in the context of a proposed central structure organized around the perception and internal representation of the space-time continuum encompassing memory, will, and other higher cognitive processes. Goldstein maintained that a unified conceptual organization and general gestalt of space-time in which all aspects of relevant sensory perception of both the physical body (i.e. via interoception) and external space (i.e. via exteroception) were integrated was necessary both for object perception as well as for successful goal-directed dynamic bodily action in relationship to extrapersonal space and the objects located therein. In his classic papers reviewing the wide variety of disconnection syndromes associated with focal brain pathology, Norman Geschwind commented that Kurt Goldstein "was perhaps the first to stress the non-unity of the personality in patients with callosal section, and its possible psychiatric effects." Anarchic hand syndrome and alien hand syndrome are two similar but separate disorders. In both there are unintended but purposeful and autonomous movements of the upper limb and intermanual conflict. Anarchic hand is usually diagnosed as opposed to alien hand syndrome because it tends to be more associated with motor impairments as the patients acknowledge the hand as theirs but are frustrated by its unintended actions. In alien hand syndrome the individual tends to display more sensory deficits as they dissociate themselves from the hand and its actions, frequently remarking on the hand's behaviour as if it does not belong to them. While Alien Hand Syndrome is very rare, it has also been documented in public cases. Rapper and poet Common has recently admitted his struggle with Alien Hand Syndrome, and spoke openly about the syndrome in a candid 2015 interview with Diane Sawyer. ==Signs and symptoms== A person with alien hand syndrome can feel normal sensation in the hand and leg, but believes that the hand, while still being a part of their body, behaves in a manner that is totally distinct from the sufferer's normal behavior. They lose the 'sense of agency' associated with the purposeful movement of the limb while retaining a sense of 'ownership' of the limb. They feel that they have no control over the movements of the 'alien' hand, but that, instead, the hand has the capability of acting autonomously—i.e., independent of their voluntary control. The hand effectively has 'a will of its own.' "Alien behavior" can be distinguished from reflexive behavior in that the former is flexibly purposive while the latter is obligatory. Sometimes the sufferer will not be aware of what the alien hand is doing until it is brought to his or her attention, or until the hand does something that draws their attention to its behavior. There is a clear distinction between the behaviors of the two hands in which the affected hand is viewed as "wayward" and sometimes "disobedient" and generally out of the realm of their own voluntary control, while the unaffected hand is under normal volitional control. At times, particularly in patients who have sustained damage to the corpus callosum that connects the two cerebral hemispheres (see also split-brain), the hands appear to be acting in opposition to each other. A related syndrome described by the French neurologist François Lhermitte involves the release through disinhibition of a tendency to compulsively utilize objects that present themselves in the surrounding environment around the patient. The behavior of the patient is, in a sense, obligatorily linked to the "affordances" (using terminology introduced by the American ecological psychologist, James J. Gibson) presented by objects that are located within the immediate peri-personal environment. This condition, termed "utilization behavior", is most often associated with extensive bilateral frontal lobe damage and might actually be thought of as "bilateral" alien hand syndrome in which the patient is compulsively directed by external environmental contingencies (e.g., the presence of a hairbrush on the table in front of them elicits the act of brushing the hair) and has no capacity to "hold back" and inhibit pre-potent motor programs that are obligatorily linked to the presence of specific external objects in the peri-personal space of the patient. When the frontal lobe damage is bilateral and generally more extensive, the patient completely loses the ability to act in a self-directed manner and becomes totally dependent upon the surrounding environmental indicators to guide his behavior in a general social context, a condition referred to as "Environmental Dependency Syndrome". In order to deal with the alien hand, some patients engage in personification of the affected hand. Usually these names are negative in nature, from mild such as “cheeky” to malicious “monster from the moon”. For example, Doody and Jankovic described a patient who named her alien hand "baby Joseph." When the hand engaged in playful, troublesome activities such as pinching her nipples (akin to biting while nursing), she would experience amusement and would instruct baby Joseph to "stop being naughty."〔 Furthermore, Bogen suggested that certain personality characteristics, such as a flamboyant personality, contribute to frequent personification of the affected hand. Neuroimaging and pathological research shows that the frontal lobe (i.e., in the frontal variant) and corpus callosum (i.e., the callosal variant) are the most common anatomical lesions responsible for the alien hand syndrome.〔 These areas are closely linked in terms of motor planning and its final pathways. The callosal variant includes advanced willed motor acts by the non-dominant hand, where patients frequently exhibit "intermanual conflict" in which one hand acts at cross-purposes with the other "good hand."〔 For example, one patient was observed putting a cigarette into her mouth with her intact, 'controlled' hand (her right, dominant hand), following which her alien, non-dominant, left hand came up to grasp the cigarette, pull the cigarette out of her mouth, and toss it away before it could be lit by the controlled, dominant, right hand. The patient then surmised that "I guess 'he' doesn't want me to smoke that cigarette." Another patient was observed to be buttoning up her blouse with her controlled dominant hand while the alien non-dominant hand, at the same time, was unbuttoning her blouse. The frontal variant most often affects the dominant hand, but can affect either hand depending on the lateralization of the damage to medial frontal cortex, and includes grasp reflex, impulsive groping toward objects or/and tonic grasping (i.e., difficulty in releasing grip).〔 In most cases, classic alien-hand signs derive from damage to the medial frontal cortex, accompanying damage to the corpus callosum.〔 In these patients the main cause of damage is unilateral or bilateral infarction of cortex in the territory supplied by the anterior cerebral artery or associated arteries.〔 Oxygenated blood is supplied by the anterior cerebral artery to most medial portions of the frontal lobes and to the anterior two-thirds of the corpus callosum, and infarction may consequently result in damage to multiple adjacent locations in the brain in the supplied territory. As the medial frontal lobe damage is often linked to lesions of the corpus callosum, frontal variant cases may also present with callosal form signs. Cases of damage restricted to the callosum however, tend not to show frontal alien-hand signs.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alien hand syndrome」の詳細全文を読む スポンサード リンク
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