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Alien hand syndrome (also known as anarchic hand or Dr. Strangelove syndrome) is an unusual neurological disorder in which one of the sufferer's hands seem to take on a mind of its own. AHS 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 other brain surgery, strokes, or infections.

Symptoms

An alien hand sufferer 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 hands can perform complex acts such as undoing buttons, removing clothing, and manipulating tools. 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.

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 (Lhermitte 1983; Lhermitte et al 1986). The behavior of the patient is, in a sense, obligatorily linked to the "affordances" (using terminology introduced by the American ecological psychologist, J.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 their behavior in a general social context, a condition also identified by Lhermitte (1986), and referred to as "Environmental Dependency Syndrome."

Sufferers of alien hand will often personify the rogue limb, for example believing it to be "possessed" by some intelligent or alien spirit or an entity that they may name or identify. 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. 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." This type of problem has been termed "intermanual conflict" or "diagonistic apraxia."

This condition has been thought to provide a fascinating window into the nature of human consciousness as it relates to voluntary action, processes underlying decision making and conscious volition, as well as the general nature of human agency and intentionality. It provides insight into the neural mechanisms involved in the emergence of a sense of agency association with bodily action. Besides its relevancy to the understanding of the neurobiologic basis of human action and volition/intentionality, these observations would appear to have significant relevance for the general philosophy of action. In that the recognition and study of this condition depends upon linking an observation of a particular behavior—the appearance of a purposeful limb action—to either a direct report or inference regarding the subjective experience of the actor associated with producing the movement, and then correlating this transformed relation with brain pathophysiology, alien hand syndrome and its study may be viewed as within the purview of neurophenomenology. Furthermore, the dissociation of the sense of agency from the sense of ownership that is observed in alien hand syndrome can also be seen in other neuropsychiatric conditions, such as schizophrenia, and may serve to help provide insight into the neural mechanisms underlying these conditions.

Subtypes

There are several distinct subtypes of Alien Hand Syndrome that appear to be associated with specific distributions of associated brain injury. Damage to the corpus callosum can give rise to "purposeful" actions in the sufferer's non-dominant hand (an individual who is left-hemisphere-dominant will experience the left hand becoming alien, and the right hand will turn alien in the person with right-hemisphere dominance) as well as a problem termed "intermanual conflict" in which the two hands appear to be directed at opposing purposes, whereas unilateral injury to the brain's frontal lobe can trigger reaching, grasping and other purposeful movements in the contralateral hand. With anteromedial frontal lobe injury, these movements are often exploratory reaching movements in which external objects are frequently grasped and utilized functionally, without the simultaneous perception on the part of the patient that they are "in control" of these movements. Once an object is maintained in the grasp of this "frontal variant" form of alien hand, the patient often has difficulty with voluntarily releasing the object from grasp and can sometimes be seen to be peeling the fingers of the hand back off the grasped object using the opposite controlled hand to enable the release of the grasped object.

A distinct "posterior variant" form of alien hand syndrome is associated with damage to the posterolateral parietal lobe and/or occipital lobe of the brain. The movements in this situation tend to be more likely to withdraw the palmar surface of the hand away from environmental contact rather than reaching out to grasp onto objects to produce palmar tactile stimulation, as is most often seen in the frontal form of the condition. Alien movements in the posterior variant of the syndrome also tend to be less coordinated and show a coarse ataxic motion during active movement that is generally not observed in the frontal form of the condition. The alien limb in the posterior variant of the syndrome may be seen to 'levitate' upward into the air and away from contact surfaces. Alien hand movement in the posterior variant may show a typical posture, sometimes referred to as a 'parietal hand' or 'instinctive avoidance reaction' (a term introduced by neurologist Derek Denny-Brown), in which the digits move into a highly extended position and the palmar surface is pulled back away from approaching objects. The 'alien' movements, however, remain purposeful and goal-directed, a point which clearly differentiates these movements from other forms of involuntary limb movement (e.g., athetosis, chorea, or myoclonus). In both the frontal and the posterior variants of the alien hand syndrome, the patient's reactions to the limb's apparent capability to perform goal-directed actions independent of conscious volition is similar. In both of these variants of alien hand syndrome, the alien hand emerges in the hand contralateral to the damaged hemisphere.

Patients thus will often indicate that the apparently purposeful movements of the alien hand are "wayward" or "disobedient," in that they are not being generated through the exertion of their own voluntary will or directed toward goals that have been consciously produced, but, instead, the alien hand appears to behave independent of conscious will, effectively "on its own." The alien hand is directed toward goals of which the patient is not consciously aware. The alien hand may even engage in socially inappropriate behavior in a public venue causing significant embarrassment and distress (Ong Hai & Odderson, 2000). Patients may react with dismay and concern at the ability of the hand to perform purposeful actions that are independent of their own conscious sense of control over the movement, a phenomenon termed "auto-criticism."

Alternatively, they may attribute the forces initiating and controlling these purposeful movements to some external being that is somehow "alien" to their self-perceived personna. For example, a particularly religious woman with alien hand syndrome, when asked who or what was actually controlling the alien movements of her hand if she was not, replied that "God must be doing all of that." Some patients choose to "personify" the hand and dissociate themselves from the behavior of the hand by giving it a proper name and attributing to it a separate and distinct personality and personhood. They may choose to "hold back" these unwanted, bothersome "alien" movements and behaviors by grasping and constraining the "wayward" hand with the controlled contralateral hand, an action that has been termed "self-restriction" or "self-grasping." Such alien movements and behaviors can also be seen in progressive degenerative diseases that produce a process of steady systematic disintegration of motor control circuitry within the central nervous system, such as Creutzfeldt-Jakob Disease, and corticobasal degeneration.

Explanatory theories

The common emerging factor in Alien Hand Syndrome is that the primary motor cortex controlling hand movement is isolated from premotor influences but remains generally intact in its ability to execute movements of the hand. A very recent fMRI study looking at the temporal sequence of activation of components of a cortical network associated with voluntary movement in normal individuals demonstrated "an anterior-to-posterior temporal gradient of activity from supplemental motor area through premotor and motor cortices to the posterior parietal cortex" (Kayser et al 2009). Therefore, with normal voluntary movement, the emergent sense of agency appears to be associated with an orderly sequence of activation that develops initially in the anteromedial frontal cortex in the vicinity of the supplementary motor complex on the medial surface of the hemisphere prior to activation of the primary motor cortex. A recent fMRI study examining the difference in functional brain activation patterns associated with alien as compared to non-alien 'volitional' movement in a patient with alien hand syndrome found that alien movement involves isolated activation of the contralateral primary motor cortex, while non-alien movement involved the activation of primary motor cortex in concert with frontal and parietal association cortex presumably involved in a cortical network generating premotor influences on the primary motor cortex (Assal et al 2007).

It is theorized that Alien Hand Syndrome results when disconnection occurs between different parts of the brain that are engaged in different aspects of the control of bodily movement. As a result, different regions of the brain are able to command bodily movements, but cannot generate a conscious feeling of self-control over these movements. As a result, the "sense of agency" that is normally associated with voluntary movement is impaired or lost. There is thus a dissociation between the process associated with the actual execution of the physical movements of the limb and the process that produces an internal sense of voluntary control over the movements, with this latter process thus normally creating the internal conscious sensation that the movements are being internally initiated, controlled and produced by an active self. Recent studies have examined the neural correlates of emergence of the sense of agency under normal circumstances (Spengler, et al 2009). This appears to involve consistent congruence between what is being produced through efferent outflow to the musculature of the body, and what is being sensed as the presumed product in the periphery of this efferent command signal. In alien hand syndrome, the neural mechanisms involved in establishing that this congruence has occurred may be impaired. This may involve an abnormality in the brain mechanism that differentiates between "re-afference" (i.e., the return of kinesthetic sensation from the self-generated 'active' limb movement) and "ex-afference" (i.e., kinesthetic sensation generated from an externally-produced 'passive' limb movement in which an active self does not participate). This brain mechanism is proposed to involve the production of a parallel "efference copy" signal that is sent directly to the somatic sensory regions and is transformed into a "corollary discharge," an expected afferent signal from the periphery that would result from the performance driven by the issued efferent signal. The correlation of the corrollary discharge signal with the actual afferent signal returned from the periphery can then be used to determine if, in fact, the intended action occurred as expected. When the sensed result of the action is congruent with the predicted result, then the action can be labelled as self-generated and associated with an emergent sense of agency. If, however, the neural mechanisms involved in establishing this sensorimotor linkage associated with self-generated action are faulty, it would be expected that the sense of agency with action would not develop.

One theory posed to explain these phenomena proposes that the brain has separable neural "premotor" or "agency" systems for managing the process of transforming intentions into overt action. An anteromedial frontal premotor system is engaged in the process of directing exploratory actions based on "internal" drive by releasing or reducing inhibitory control over such actions. Damage to this system produces disinhibition and release of such actions which then occur autonomously. A posterolateral temporo-parieto-occipital premotor system has a similar inhibitory control over actions that withdraw from environmental stimuli as well as the ability to excite actions that are contingent upon and driven by external stimulation, as distinct from internal drive. These two hemispheric systems interact through mutual inhibition that maintains a balance between responding to and withdrawing from environmental stimuli in the behavior of the contralateral limbs (Denny-Brown, 1956, 1958, 1966). Together, these hemispheric agency systems form an integrated intrahemispheric agency system.

When the anteromedial frontal system is damaged, involuntary but purposive movements of an exploratory reach-and-grasp nature--what Denny-Brown (1956, 1966) referred to as a positive cortical tropism--are released in the contralateral limb. When the posterolateral parieto-occipital system is damaged, involuntary purposive movements of a release-and-retract nature, such as levitation and instinctive avoidance, are released. Furthermore, each intrahemispheric agency system has the capability of acting autonomously in its control over the contralateral limb although unitary integrative control of the two hands is maintained through interhemispheric communication between these systems via the projections traversing the corpus callosum at the cortical level and other interhemispheric commissures linking the two hemispheres at the subcortical level. Thus, human agency can be thought of as emerging through the linked and coordinated action of at least four major agency systems, two in each hemisphere.

The critical difference between the two hemispheres, however, is the direct connection between the agency system of the dominant hemisphere and the encoding system based primarily in the dominant hemisphere that links action production and its interpretation with language. Thus, the overarching unitary conscious agent that emerges in the intact brain is based primarily in the dominant hemisphere and is closely connected to the organization of language capacity. It is proposed that while action precedes linguistic capacity during development, a process ensues through the course of development through which linguistic constructs are linked to action elements in order to produce a language-based encoding of action-oriented knowledge. Through this process of basically "telling oneself a story" about how an act occurs, a language-based "action-capable" self is constructed through consistent correlations between intended actions and subsequent perceived outcomes.

When there is a major disconnection between the two hemispheres resulting from callosal injury, the language-linked dominant hemisphere agent which maintains its primary control over the dominant limb effectively loses its direct and linked control over the separate "agent" based in the nondominant hemisphere (and, thus, the nondominant limb), which had been previously responsive and "obedient" to the dominant conscious agent. The possibility of purposeful action occurring outside of the realm of influence of the conscious dominant agent, thus can occur and the basic assumption that both hands are controlled through and subject to the dominant agent is proven incorrect. The sense of agency that would normally arise from movement of the nondominant limb now no longer develops, or, at least, is no longer accessible to consciousness. A new explanatory "story" for understanding the nature of the inaccessible agent moving the nondominant limb is thus necessitated.

Under such circumstances, the two agents therefore can direct actions in the two limbs that are directed at opposing purposes although the dominant hand remains linked to the dominant consciously accessible agent and is thus viewed as continuing to be under "conscious control" and obedient to conscious will, while the nondominant hand is no longer "tied in" to the dominant agent and is thus identified by the conscious language-based dominant agent as having a separate and alien agency. This theory would explain the emergence of alien behavior in the nondominant limb and intermanual conflict between the two limbs in the presence of damage to the corpus callosum. The distinct anteromedial frontal and posterolateral temporo-parieto-occipital forms of the alien hand syndrome would be explained by selective injury to either the frontal or the posterior agency systems within a particular hemisphere, with the alien behavior developing in the limb contralateral to the damaged hemisphere.

Proposed strategies for treatment

Although there is no known formal (primary) treatment for Alien Hand Syndrome at this time, the symptoms can be reduced and managed to some degree by keeping the alien hand occupied and involved in a task, for example by giving it an object to hold in its grasp. Also, specific learned tasks can restore voluntary control of the hand to a significant degree. For example, one patient with the "frontal" form of alien hand who would reach out to grasp onto different objects (e.g., door handles) as he was walking, was given a cane to hold in the alien hand while walking, even though he really did not need a cane for its usual purpose of assisting with balance and facilitating ambulation. With the cane firmly in the grasp of the alien hand, it would generally not release the grasp and drop the cane in order to reach out to grasp onto a different object. Thus, different strategies can be employed to reduce the interference of the alien hand behavior on the ongoing coherent controlled bodily actions of the patient.

Furthermore, in the presence of unilateral damage to a single cerebral hemisphere, there is generally a gradual reduction in the frequency of alien behaviors observed over time and a gradual restoration of voluntary control over the affected hand, suggesting that neuroplasticity in the bihemispheric and subcortical brain systems involved in voluntary movement production can serve to re-establish the connection between the executive production process and the internal self-generation and registration process. Exactly how this may occur is not well-understood but a process of gradual recovery from alien hand syndrome when the damage involves a single hemisphere has been reported.

In another approach, the patient is trained to perform a specific task, such as moving the alien hand to contact a specific object or a highly salient environmental target, which is a movement that the patient can learn to generate voluntarily through focused training in order to effectively override the alien behavior. It is possible that some of this training produces a re-organization of premotor systems within the damaged hemisphere, or, alternatively, that ipsilateral control of the limb from the intact hemisphere may be expanded. Yet another approach involves simultaneously "muffling" the action of the alien hand and limiting the sensory feedback coming back to the hand from environmental contact by placing it in a restrictive "cloak" such as a specialized soft foam hand orthosis or, alternatively, an everyday oven mitt. Of course, this then limits the degree to which the hand can participate in addressing functional goals for the patient. Theoretically, this approach could slow down the process through which voluntary control of the hand is restored if the neuroplasticity that underlies recovery involves the exercise of voluntary will to control the actions of the hand in a functional context.

Notes

This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. Please help improve this article by introducing more precise citations. (September 2009) (Learn how and when to remove this message)

1. "The Mind's Strange Syndroms". BBC News. September 8, 2000. "Even today, "anarchic hand" has earned the popular sobriquet Dr Strangelove syndrome - named after the eponymous scientist with the unruly limb in Stanley Kubrick's 1964 film."

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Pop cultural references

This article contains a list of miscellaneous information. Please relocate any relevant information into other sections or articles.

The theme of hands and other limbs outside the owner's control is a common one in pop culture, especially comedy, although not every example of such can be considered as Alien hand syndrome per se. Some examples which are relevant include:

• The character Dr. Strangelove in the movie Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb suffers from the syndrome. His hand seems to act in a more complex manner, so that it acts in accordance with his subconscious urges (e.g. attempting to strangle himself, giving a Nazi salute,).

Works cited

• Bellows, Allen. "Alien Hand Syndrome." Damn Interesting. 19 Nov. 2005. 13 Dec. 2008 <http://www.damninteresting.com/?p=203.>
• Bryant, Charles W. "How Alien Hand Syndrome Works." HowStuffWorks. 19 June 2005. 15 Dec. 2008 <http://health.howstuffworks.com/alien-hand.htm.>
• "Defininition of Alien Hand Syndrome." MedicalNet.com. 4 Oct. 2008. Dec.-Jan. 2008 <http://www.medterms.com/script/main/art.asp?articlekey=12655>.

External links

• Recent review article on Alien Hand Syndrome by LA Scepkowski & A Cronin-Golomb
• Editorial paper regarding the different forms of Alien Hand Syndrome by G Goldberg
• Recent review article from the Archives of Neurology by I. Biran and A. Chatterjee
• Videos inspired by the syndrome?
• Information about the rare disorder, as well as how many times it has influenced the media.

• Neurological disorders