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Alien hand syndrome (AHS) or Dr. Strangelove syndrome is a rare movement disorder, 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. There are many similar terms for the various forms of the condition, but they are often used inappropriately. The afflicted limb may perform meaningful movements, such as 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, thought, as 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 "disentanglement" between thought and action. Patients are aware that the affected limb is still a part of their body but report feeling as if it is an external agent, and often describe it in the third person .

Alien hand syndrome is best documented in cases where a person has had the two hemispheres of their brain surgically separated,[citation needed] a procedure sometimes used to relieve the symptoms of extreme cases of epilepsy and epileptic psychosis, e.g., temporal lobe epilepsy. It also occurs in some cases after brain surgery, stroke, infection, tumor, aneurysm, migraine and specific degenerative brain conditions such as Alzheimer's disease, Corticobasal degeneration and Creutzfeldt–Jakob disease.[citation needed] (SENTENCE REMOVED). '''Lesions to different lobes of the brain are also thought to be a cause of this disorder. This includes lesions of the "supplementary motor area (SMA), anterior cingulate, corpus callosum, anterior prefrontal cortex, posterior parietal cortex, and thalamus". The neural mechanisms of this movement disorder remains unclear but it has been proposed that unwanted movements may due to a release of the primary motor cortex (M1) from conscious control by intentional planning systems .'''

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. There are three main types of alien hand syndrome. According to Qureshi et al., (2016) there are "two are frontal varieties, of which one is linked to lesions of the language dominant medial frontal cortex and the anterior corpus callosum affecting dominant hand, and the other involves the corpus callosum alone and affects the non-dominant hand".