Human θ burst stimulation enhances subsequent motor learning and increases performance variability.

Area of Science:

• Neuroscience
• Motor Control
• Neuroplasticity

Background:

• Intermittent theta burst stimulation (iTBS) transiently increases motor cortex excitability, potentially via long-term potentiation (LTP).
• Nicotine is known to enhance iTBS-induced cortical excitability.
• Motor task acquisition involves increased cortical excitability and presumed intracortical LTP.

Purpose of the Study:

• To investigate the effects of iTBS and nicotine on subsequent motor learning.
• To explore mechanisms beyond synaptic strengthening that might influence motor learning.
• To determine if iTBS influences motor output variability and if nicotine modulates this effect.

Main Methods:

• A double-blinded, placebo-controlled trial involving ten healthy subjects.
• Administration of iTBS and nicotine (or placebo).
• Assessment of motor learning rates, performance variability, and transcranial magnetic stimulation (TMS)-evoked motor output.

Main Results:

• iTBS alone significantly increased the rate of motor learning.
• Nicotine administration blocked the learning-enhancing effect of iTBS.
• iTBS increased motor performance variability, which correlated with learning outcomes; nicotine negated this variability increase.

Conclusions:

• iTBS facilitates motor learning not only through synaptic plasticity but also by increasing motor output variability.
• Nicotine counteracts the beneficial effects of iTBS on motor learning, possibly by modulating the signal-to-noise ratio in the cerebral cortex.
• These findings highlight complex interactions between neuromodulation, synaptic plasticity, and motor output variability in motor learning.