Supplementary motor area activations in unconscious inhibition of voluntary action.
It is widely accepted that regions within the dorsal medial frontal cortex are involved in the control of voluntary action. However, recent evidence suggests that a subset of these regions may also be important for unconscious and involuntary motor processes. Indeed, Sumner et al. (Neuron 54:697-711, 2007) showed that two patients with micro-lesions of the supplementary motor area (SMA) and supplementary eye field (SEF) demonstrated an absence of unconscious inhibition as evoked by masked-prime stimuli, while pre-SMA damage had no such effect. Here, we employ fMRI and a similar masked-prime task to test whether SMA and pre-SMA are similarly dissociated in healthy volunteers. Reaction times (RT) revealed that responses to compatible trials were slower than those to incompatible trials (negative compatibility effect, NCE), indicating automatic inhibition in every participant. BOLD signals in the SMA were modulated by prime compatibility, showing greater signal for compatible trials, but there was no change in pre-SMA. There was also no modulation in the hand motor cortex (HMC). These findings imply that the SMA is involved in automatic suppression of manual motor plans.
Boy
Frédéric
F
School of Psychology, Cardiff University, Tower Building, Park place, Cardiff, CF10 3AT, UK. boyf@cf.ac.uk
Husain
Masud
M
Singh
Krish D
KD
Sumner
Petroc
P
D000328:Adult; D001931:Brain Mapping; D004192:Discrimination, Psychological; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006225:Hand / Q000294:innervation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007266:Inhibition, Psychological; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009044:Motor Cortex / Q000098:blood supply / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010470:Perceptual Masking / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D014473:Unconscious, Psychology
D010100:Oxygen