title: Reversed Procrastination by Focal Disruption of Medial Frontal Cortex.
abstract: An enduring puzzle in the neuroscience of voluntary action is the origin of the remarkably wide dispersion of the reaction time distribution, an interval far greater than is explained by synaptic or signal transductive noise [1, 2]. That we are able to change our planned actions-a key criterion of volition [3]-so close to the time of their onset implies decision-making must reach deep into the execution of action itself [4-6]. It has been influentially suggested the reaction time distribution therefore reflects deliberate neural procrastination [7], giving alternative response tendencies sufficient time for fair competition in pursuing a decision threshold that determines which one is behaviorally manifest: a race model, where action selection and execution are closely interrelated [8-11]. Although the medial frontal cortex exhibits a sensitivity to reaction time on functional imaging that is consistent with such a mechanism [12-14], direct evidence from disruptive studies has hitherto been lacking. If movement-generating and movement-delaying neural substrates are closely co-localized here, a large-scale lesion will inevitably mask any acceleration, for the movement itself could be disrupted. Circumventing this problem, here we observed focal intracranial electrical disruption of the medial frontal wall in the context of the pre-surgical evaluation of two patients with epilepsy temporarily reversing such hypothesized procrastination. Effector-specific behavioral acceleration, time-locked to the period of electrical disruption, occurred exclusively at a specific locus at the ventral border of the pre-supplementary motor area. A cardinal prediction of race models of voluntary action is thereby substantiated in the human brain.
authors: Institute of Neurology, UCL, Queen Square, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors: Ashwani
authors: A
authors: Jha
authors: Institute of Neurology, UCL, Queen Square, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors: Beate
authors: B
authors: Diehl
authors: Institute of Neurology, UCL, Queen Square, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors: Catherine
authors: C
authors: Scott
authors: Institute of Neurology, UCL, Queen Square, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors: Andrew W
authors: AW
authors: McEvoy
authors: Institute of Neurology, UCL, Queen Square, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK. Electronic address: p.nachev@ucl.ac.uk.
authors: Parashkev
authors: P
authors: Nachev
mesh_terms: D000328:Adult; D004827:Epilepsy / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D017397:Prefrontal Cortex / Q000502:physiology*; D000075682:Procrastination; D011930:Reaction Time; D014836:Volition
keywords: brain image registration; direct cortical stimulation; pre-supplementary motor area; race models of decision-making; voluntary action