title: When the brain changes its mind: flexibility of action selection in instructed and free choices.
abstract: The neural mechanisms underlying the selection and initiation of voluntary actions in the absence of external instructions are poorly understood. These mechanisms are usually investigated using a paradigm where different movement choices are self-generated by a participant on each trial. These "free choices" are compared with "instructed choices," in which a stimulus informs subjects which action to make on each trial. Here, we introduce a novel paradigm to investigate these modes of action selection, by measuring brain processes evoked by an instruction to either reverse or maintain free and instructed choices in the period before a "go" signal. An unpredictable instruction to change a response plan had different effects on free and instructed choices. In instructed trials, change cues evoked a larger P300 than no-change cues, leading to a significant interaction of choice and change condition. Free-choice trials displayed a trend toward the opposite pattern. These results suggest a difference between updating of free and instructed action choices. We propose a theoretical framework for internally generated action in which representations of alternative actions remain available until a late stage in motor preparation. This framework emphasizes the high modifiability of voluntary action.
authors.affiliation: Institute of Cognitive Neuroscience, University College London, UK. s.fleming@fil.ion.ucl.ac.uk
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Fleming
authors.forename: Rogier B
authors.initials: RB
authors.lastname: Mars
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Gladwin
authors.forename: Patrick
authors.initials: P
authors.lastname: Haggard
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology*; D003463:Cues; D004569:Electroencephalography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009068:Movement / Q000502:physiology; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted