I read with great interest the recent paper by Bundick and Spinella1 and the related commentary by Goldberg.2 These articles address the neurological substrates of volitional disturbance and in places they adopt the vocabulary of the philosophy of action—for example, Goldberg refers to the “will”. However, their uses of action related terms are mutually inconsistent and some clarification might assist in elucidating the functional anatomical relevance of the disorders described.

If we are to use the terms “will” and “action” then their use should be internally consistent. The “will” is that process that deliberates (consciously) on what is to be done, and the “action” is the performance, which follows on from that deliberation.3 4 (It should be noted that the temporal sequence of this philosophical model of volition is substantially undermined by the classic EEG experiments of Libetet al on “intention”.5 6) An “action” is consciously chosen; there is no such thing as an “involuntary action” (according to this model). Involuntary movements are movements not theintended actions of the agent (“the one who acts”).4 It follows that the movements initiated by an “alien hand” may seem purposeful, but they are not actions (chosen by the patient). They are failures of action in so far as the patient cannot make the limb “behave”. Hence, although Goldberg refers to the “will” being involved in action generation, his terminology is extrapolated inconsistently: he refers to alien hands performing “purposeful acts” and “involuntary actions”2; the first is an attribute of an agent, the second is an oxymoron.4

Bundick and Spinella, by contrast, refer to “involuntary motor activity” and “non-purposeful” movements.1 These terms are coherent within the context of the “will” vocabulary being used.

The above points are not merely pedantic, as a case can be made for “action” and “agency” implicating different brain systems,7 and thus the volitional deficit demonstrated in each form of the alien hand syndrome may have some cognitive-neurobiological relevance.

In the medial-prefrontal and callosal forms of alien hand syndrome, the patients, although they have a failure of motor control, and an inability to impose their “will” on the alien limb, do not generally attribute alien agency to that limb—that is, they do not experience it as belonging to an “other”. However, in the posterior alien hand syndrome, personal agency may be lost, and the limb experienced as belonging to someone else. Consider the case of Leiguarda et al,8 cited by neither Bundick and Spinella nor Goldberg.1 2 This alien limb (associated with ictal activity from a right parietal lesion) was experienced thus by the patient:

”Suddenly I had a strange feeling on my left side; later I could not recognize the left arm as my own; I felt it belonged to someone else and wanted to hurt me because it moved towards me”.8

This third form of alien hand syndrome has been referred to previously.7 The loss of agency it comprises is consistent with that alienation noted in “somatoparaphrenia” by Critchley9 and is congruent with that attribution of agency to external forces so characteristic of schizophrenic “alien control”; itself associated with functional abnormality of the right parietal region.10

Hence, a consistent application of action terminology may help to elucidate the functional anatomical correlates of disorders of volition.7