Alien hand syndrome (AHS) or Dr. Strangelove syndrome is a category of conditions in which a person experiences their limbs acting seemingly on their own, without conscious control over the actions. There are a variety of clinical conditions that fall under this category, which most commonly affects the left hand.
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 controllable hand to restrain the alien hand. While under normal circumstances, as thought, intent and action can be assumed to be deeply mutually entangled, the occurrence of alien hand syndrome can be usefully conceptualized as a phenomenon reflecting a functional divorce between thought and action.
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 and epileptic psychosis.
It also occurs in some cases after brain surgery, a stroke, infection, a tumor, a migraine and specific degenerative brain conditions such as Alzheimer’s disease.
The common emerging factor in alien hand syndrome is that the primary motor cortex controlling hand movement is isolated from premotor cortex influences but remains generally intact in its ability to execute movements of the hand.
Premotor cortex – motor area anterior to (in front of) the primary motor cortex. The premotor cortex is thought to be involved in the planning of movements but also has a number of other functions that are still poorly understood.
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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 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 (the process that normally creates the internal conscious sensation that the movements are being internally initiated, controlled and produced by an active self.)
Patient 1. The patient suffered from a symptom characterized by involuntary mirror movements of the affected hand. When the patient was asked to perform movements with one hand, the other hand would involuntarily perform a mirror image movement which continued even when the involuntary movement was brought to the attention of the patient.
The patient described the left hand as frequently interfering and taking over anything the patient tried to do with the right hand. For instance, when trying to grasp a glass of water with the right hand with a right side approach, the left hand would involuntary reach out and grasp hold of the glass through a left side approached.
Patient 2. One week after undergoing coronary artery bypass grafting, a woman noticed that her left hand started to “live a life of its own”. It would unbutton her gown, try to choke her while asleep and would automatically fight with the right hand to answer the phone.
She had to physically restrain the affected hand with the right hand to prevent injury, a behavior which has been termed “self-restriction”.
There is no cure for the alien hand syndrome. However, 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. Specific learned tasks can restore voluntary control of the hand to a significant degree.
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.