Gary Goldberg says:

I have published a number of papers and collected videos of individuals who present with alien hand syndrome in connection with specifically localized brain lesions. The development of alien hand phenomena in the context of brain injury can be viewed as a fascinating window into the normal operation of the mind and consciousness at least as it relates to the concepts of volition, voluntary will and the neurobiologic basis of purposeful action. There is the general issue that the normal experience of causal relationship between a sense of internal control over limb movement and the overt manifestation of internal will in terms of the appearance of purposeful body movement occurs through a specifically constrained neurobiologic process. When things go well, there is "connection" between the internal experience and the overt manifestation. However, when things get "de-railed" through various pathologies, a disconnection develops between the internal experience of volition and the overt external manifestation of movement. The result can be quite extraordinary with some clinical "stories" that are of general interest, I think.