title: Functional specificity of human premotor-motor cortical interactions during action selection.
abstract: Functional connections between dorsal premotor cortex (PMd) and primary motor cortex (M1) have been revealed by paired-pulse transcranial magnetic stimulation (TMS). We tested if such connections would be modulated during a cognitive process (response selection) known to rely on those circuits. PMd-M1 TMS applied 75 ms after a cue to select a manual response facilitated motor-evoked potentials (MEPs). MEPs were facilitated at 50 ms in a control task of response execution, suggesting that PMd-M1 interactions at 75 ms are functionally specific to the process of response selection. At 100 ms, PMd-M1 TMS delayed choice reaction time (RT). Importantly, the MEP (at 75 ms) and the RT (at 100 ms) effects were correlated in a way that was hand-specific. When the response was made with the M1-contralateral hand, MEPs correlated with slower RTs. When the response was made with the M1-ipsilateral hand, MEPs correlated with faster RTs. Paired-pulse TMS confined to M1 did not produce these effects, confirming the causal influence of PMd inputs. This study shows that a response selection signal evolves in PMd early during the reaction period (75-100 ms), impacts on M1 and affects behaviour. Such interactions are temporally, anatomically and functionally specific, and have a causal role in choosing which movement to make.
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK. jacinta.oshea@psy.ox.ac.uk
authors.forename: Jacinta
authors.initials: J
authors.lastname: O'Shea
authors.forename: Catherine
authors.initials: C
authors.lastname: Sebastian
authors.forename: Erie D
authors.initials: ED
authors.lastname: Boorman
authors.forename: Heidi
authors.initials: H
authors.lastname: Johansen-Berg
authors.forename: Matthew F S
authors.initials: MF
authors.lastname: Rushworth
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002755:Choice Behavior / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation