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

Figure 2

Normalized MEP amplitudes of 6 subjects with 95% confidence interval of each protocol. One-way repeated-measures ANOVA showed a statistically significant inhibition, an LTD-like effect, of protocol of 1-minute stimulation of 0.25 Hz (reporting as an uncorrected value) ((b); diamond shape; value < 0.05). Post hoc analysis of this protocol showed that the inhibitory effect (reporting as an uncorrected value) began immediately after applying (T1), 10 (T10), 15 (T15), and 20 minutes (T20) ( value < 0.05). The maximum inhibition was approximately 70% reduction. The protocols of 2-minute stimulation of 0.2 Hz (a), 0.25 Hz ((b) square shape), and 0.5 Hz ((c) square shape) and 1-minute stimulation of 0.5 Hz ((c) diamond shape) and 1 Hz (d) did not show either inhibition or facilitation. Min = minute, MEP = motor-evoked potentials, LTD = long-term depression, and = paired associative stimulation with interstimulus interval of 10 ms.

(a)

(b)

(c)

(d)