Repetitive stimulation of premotor cortex affects primary motor cortex excitability and movement preparation.
BACKGROUND
Repetitive transcranial magnetic stimulation can be used to explore functional connectivity between cortical areas.


OBJECTIVE
To determine the effects of two theta burst stimulation (TBS) patterns (intermittent, iTBS; and continuous, cTBS) of left dorsal premotor cortex (PMd).


METHODS
Left PMd was identified in 11 participants using functional magnetic resonance imaging (fMRI), during performance of complex sequential finger movements. Each participant received iTBS, cTBS, or sham TBS of left PMd in three separate sessions within a randomized, single-blind design. The speed and accuracy of simple and complex sequential reaction time (RT) task performance was measured before and after TBS. The excitability of primary motor cortex (M1) bilaterally, and interhemispheric facilitation from left PMd to right M1, were also measured before and after TBS.


RESULTS
iTBS sped up the preparation of complex sequences performed with the right hand, with no detectable changes in M1 excitability. RT performance was maintained after cTBS, in the presence of increased left M1 excitability and suppressed right M1 excitability.


CONCLUSIONS
Facilitatory and inhibitory TBS protocols applied to left PMd differentially alter corticomotor excitability and behavior, which suggests that these protocols affect different neuronal populations.
Stinear
Cathy M
CM
Movement Neuroscience Laboratory, Department of Sport and Exercise Science, University of Auckland, Auckland, New Zealand. c.stinear@auckland.ac.nz
Barber
P Alan
PA
Coxon
James P
JP
Verryt
Toby S
TS
Acharya
Pratima P
PP
Byblow
Winston D
WD
D000368:Aged; D019054:Evoked Potentials, Motor; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement; D011930:Reaction Time; D013826:Theta Rhythm; D050781:Transcranial Magnetic Stimulation / Q000379:methods