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Intermittent theta burst stimulation (iTBS) transiently increases motor cortex excitability in healthy humans by a process thought to involve synaptic long-term potentiation (LTP), and this is enhanced by nicotine. Acquisition of a ballistic motor task is likewise accompanied by increased excitability and presumed intracortical LTP. Here, we test how iTBS and nicotine influences subsequent motor learning. Ten healthy subjects participated in a double-blinded placebo-controlled trial testing the effects of iTBS and nicotine. iTBS alone increased the rate of learning but this increase was blocked by nicotine. We then investigated factors other than synaptic strengthening that may play a role. Behavioral analysis and modeling suggested that iTBS increased performance variability, which correlated with learning outcome. A control experiment confirmed the increase in motor output variability by showing that iTBS increased the dispersion of involuntary transcranial magnetic stimulation-evoked thumb movements. We suggest that in addition to the effect on synaptic plasticity, iTBS may have facilitated performance by increasing motor output variability; nicotine negated this effect on variability perhaps via increasing the signal-to-noise ratio in cerebral cortex.

Original publication

DOI

10.1093/cercor/bhq231

Type

Journal article

Journal

Cereb Cortex

Publication Date

07/2011

Volume

21

Pages

1627 - 1638

Keywords

Acoustic Stimulation, Adult, Female, Humans, Learning, Long-Term Potentiation, Male, Motor Cortex, Motor Skills, Nicotine, Photic Stimulation, Psychomotor Performance, Theta Rhythm, Transcranial Magnetic Stimulation