Abstract
Voluntary actions are often accompanied by a conscious experience of intention. The content of this experience, and its neural basis, remain controversial. On one view, the mind just retrospectively ascribes intentions to explain the occurrence of actions that lack obvious triggering stimuli. Here, we use EEG frequency analysis of sensorimotor rhythms to investigate brain activity when a participant (CL, co-author of this paper) with congenital absence of the left hand and arm, prepared and made a voluntary action with the right or the phantom “left hand”. CL reported the moment she experienced the intention to press a key. This timepoint was then used as a marker for aligning and averaging EEG. In a second condition, CL was asked to prepare the action on all trials, but then, on some trials, to cancel the action at the last moment. For the right hand, we observed a typical reduction in beta-band spectral power prior to movement, followed by beta rebound after movement. When CL prepared but then cancelled a movement, we found a characteristic EEG pattern reported previously, namely a left frontal increase in spectral power close to the time of the perceived intention to move. Interestingly, the same neural signatures of positive and inhibitory volition were also present when CL prepared and inhibited movements with her phantom left hand. These EEG signals were all similar to those reported previously in a group of 14 healthy volunteers. Our results suggest that conscious intention may depend on preparatory brain activity, and not on making, or ever having made, the corresponding physical body movement. Accounts that reduce conscious volition to mere retrospective confabulation cannot easily explain our participant's neurophenomenology of action and inhibition. In contrast, the results are consistent with the view that specific neural events prior to movement may generate conscious experiences of positive and negative volition.
Highlights
Some voluntary actions are accompanied by an experience of conscious intention, of initiating and controlling our actions
In the condition where CL could freely choose to inhibit on certain trials, she chose to do so on 53% of trials for the right hand, and reported doing so for 46% of trials for the “left hand”
We show that a participant (CL) with congenital absence of the left hand and arm showed three classic central markers of volition with respect to simple movements of the left hand
Summary
Some voluntary actions are accompanied by an experience of conscious intention, of initiating and controlling our actions. The basis of this experience of conscious intention is vigorously debated. The experience of conscious intention is not so much a direct read-out of any specific brain activity, but an inference about the causes of internally-generated actions. One might infer that one's own actions have some internal cause by n Corresponding author at: Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, Psychology and Neuroscience, King's College London, De Crespigny Park, London SE5 8AF, United Kingdom.
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