Inducing LTD-Like Effect in the Human Motor Cortex with Low Frequency and Very Short Duration Paired Associative Stimulation: An Exploratory Study

Abstract EN

Introduction.

Paired associative stimulation (PAS) is an established technique to investigate synaptic plasticity in the human motor cortex (M1).

Classically, to induce long-term depression- (LTD-) or long-term potentiation-like effects in the human M1, studies have used low frequency and long duration trains of PAS.

In the present study, we explored an LTD-like effect using very short duration and low frequency of P A S 10 m s protocols in human M1.

Methods.

Six protocols of low frequency P A S 10 m s (ranging from 0.2 Hz to 1 Hz) were investigated with very short durations of 1 and 2 minutes stimulation.

Six healthy volunteers were included in each protocol.

We obtained motor-evoked potentials from right abductor pollicis brevis muscle before and after applying P A S 10 m s up to 30 minutes.

After we found P A S 10 m s protocol which induced an LTD-like effect, we tested that protocol on additional 5 subjects.

Results.

One-way repeated-measures ANOVA showed that only the group of 1-minute stimulation of 0.25 Hz induced an LTD-like effect.

When adding the additional subjects, the effect remained and lasted for 30 minutes.

Conclusion.

Low frequency and very short duration of P A S 10 m s potentially induced an LTD-like effect in human M1.

With further verification, this method might be useful for research relating to synaptic plasticity by reducing the duration of study and minimizing subject discomfort.