title: Individual differences in subconscious motor control predicted by GABA concentration in SMA.
abstract: Subliminal visual stimuli affect motor planning, but the size of such effects differs greatly between individuals. Here, we investigated whether such variation may be related to neurochemical differences between people. Cortical responsiveness is expected to be lower under the influence of more of the main inhibitory neurotransmitter, GABA. Thus, we hypothesized that, if an individual has more GABA in the supplementary motor area (SMA)--a region previously associated with automatic motor control--this would result in smaller subliminal effects. We measured the reversed masked prime--or negative compatibility--effect, and found that it correlated strongly with GABA concentration, measured with magnetic resonance spectroscopy. This occurred specifically in the SMA region, and not in other regions from which spectroscopy measurements were taken. We replicated these results in an independent cohort: more GABA in the SMA region is reliably associated with smaller effect size. These findings suggest that, across individuals, the responsiveness of subconscious motor mechanisms is related to GABA concentration in the SMA.
authors.affiliation: Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, Cardiff CF10 3AT, UK.
authors.forename: Frederic
authors.initials: F
authors.lastname: Boy
authors.forename: C John
authors.initials: CJ
authors.lastname: Evans
authors.forename: Richard A E
authors.initials: RA
authors.lastname: Edden
authors.forename: Krish D
authors.initials: KD
authors.lastname: Singh
authors.forename: Masud
authors.initials: M
authors.lastname: Husain
authors.forename: Petroc
authors.initials: P
authors.lastname: Sumner
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D006801:Humans; D007206:Individuality; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009483:Neuropsychological Tests; D014473:Unconscious, Psychology; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D005680:gamma-Aminobutyric Acid