Maria Concetta Pellicciari1, Carlo Miniussi2, Clarissa Ferrari3, Giacomo Koch4, Marta Bortoletto3. 1. Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy. Electronic address: mariaconcetta.pellicciari@cognitiveneuroscience.it. 2. Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy; Neuroscience Section, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy. 3. Cognitive Neuroscience Section, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy. 4. Non-invasive Brain Stimulation Unit, Department of Clinical and Behavioral Neurology, IRCCS Santa Lucia Foundation, Rome, Italy; Stroke Unit, Department of Neuroscience, Policlinic Tor Vergata, Rome, Italy.
Abstract
OBJECTIVE: To evaluate the effects of several single TMS pulses, delivered at two different inter-trial intervals (ITIs), on corticospinal excitability. METHODS: Twelve healthy volunteers participated in two experimental sessions, during which TMS pulses were delivered at random or at fixed ITIs. The TMS single pulse-induced modulation of corticospinal output (motor evoked potential amplitude - MEP) was evaluated on-line. Each session began with a baseline block, followed by 10 blocks, with 20 TMS pulses each. Intra- and inter-block effects were valuated using an ANOVA model, through nested random effect on subjects considering the subject-specific variability. RESULTS: The delivery of successive TMS pulses significantly changed both intra-block and inter-block cortical excitability, as demonstrated by an increase in the amplitude of MEPs (p<0.001) and supported through trend analyses, showing a perfect linear trend for inter-block levels (R(2)=1) and nearly linear trend for intra-block levels (R(2)=0.97). The MEPs significantly increased when the TMS pulses were delivered at both random and fixed ITIs. CONCLUSIONS: Single TMS pulses induce cumulative changes in neural activity during the same stimulation, resulting in a motor cortical excitability increase. SIGNIFICANCE: Particular attention should be taken when several single TMS pulses are delivered in research and clinical settings for diagnostic and therapeutic purposes.
OBJECTIVE: To evaluate the effects of several single TMS pulses, delivered at two different inter-trial intervals (ITIs), on corticospinal excitability. METHODS: Twelve healthy volunteers participated in two experimental sessions, during which TMS pulses were delivered at random or at fixed ITIs. The TMS single pulse-induced modulation of corticospinal output (motor evoked potential amplitude - MEP) was evaluated on-line. Each session began with a baseline block, followed by 10 blocks, with 20 TMS pulses each. Intra- and inter-block effects were valuated using an ANOVA model, through nested random effect on subjects considering the subject-specific variability. RESULTS: The delivery of successive TMS pulses significantly changed both intra-block and inter-block cortical excitability, as demonstrated by an increase in the amplitude of MEPs (p<0.001) and supported through trend analyses, showing a perfect linear trend for inter-block levels (R(2)=1) and nearly linear trend for intra-block levels (R(2)=0.97). The MEPs significantly increased when the TMS pulses were delivered at both random and fixed ITIs. CONCLUSIONS: Single TMS pulses induce cumulative changes in neural activity during the same stimulation, resulting in a motor cortical excitability increase. SIGNIFICANCE: Particular attention should be taken when several single TMS pulses are delivered in research and clinical settings for diagnostic and therapeutic purposes.
Keywords:
Corticospinal excitability; Motor evoked potentials (MEP); Random and fixed inter-trial interval; Single pulse; Transcranial magnetic stimulation (TMS)
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