Excitability modulation of the motor system induced by transcranial direct current stimulation: A multimodal approach
Articolo
Data di Pubblicazione:
2013
Abstract:
Anodal and cathodal transcranial direct current stimulations (tDCS) are both established techniques to induce
cortical excitability changes. Typically, in the human motor system, such cortical modulations are inferred
through changes in the amplitude of the motor evoked potentials (MEPs). However, it is now possible to directly
evaluate tDCS-induced changes at the cortical level by recording the transcranial magnetic stimulation
evoked potentials (TEPs) using electroencephalography (EEG).
The present study investigated the modulation induced by the tDCS on the motor system. The study evaluates
changes in the MEPs, in the amplitude and distribution of the TEPs, in resting state oscillatory brain activity
and in behavioral performance in a simple manual response task. Both the short- and long-term tDCS effects
were investigated by evaluating their time course at ~0 and 30 min after tDCS.
Anodal tDCS over the left primary motor cortex (M1) induced an enhancement of corticospinal excitability,
whereas cathodal stimulation produced a reduction. These changes in excitability were indexed by changes
in MEP amplitude. More interestingly, tDCS modulated the cortical reactivity, which is the neuronal activity
evoked by TMS, in a polarity-dependent and site-specific manner. Cortical reactivity increased after anodal
stimulation over the left M1, whereas it decreased with cathodal stimulation. These effects were partially
present also at long term evaluation.
No polarity-specific effect was found either on behavioral measures or on oscillatory brain activity. The latter
showed a general increase in the power density of low frequency oscillations (theta and alpha) at both stimulation
polarities.
Our results suggest that tDCS is able to modulate motor cortical reactivity in a polarity-specific manner, inducing
a complex pattern of direct and indirect cortical activations or inhibitions of the motor system-related network,
which might be related to changes in synaptic efficacy of the motor cortex.
cortical excitability changes. Typically, in the human motor system, such cortical modulations are inferred
through changes in the amplitude of the motor evoked potentials (MEPs). However, it is now possible to directly
evaluate tDCS-induced changes at the cortical level by recording the transcranial magnetic stimulation
evoked potentials (TEPs) using electroencephalography (EEG).
The present study investigated the modulation induced by the tDCS on the motor system. The study evaluates
changes in the MEPs, in the amplitude and distribution of the TEPs, in resting state oscillatory brain activity
and in behavioral performance in a simple manual response task. Both the short- and long-term tDCS effects
were investigated by evaluating their time course at ~0 and 30 min after tDCS.
Anodal tDCS over the left primary motor cortex (M1) induced an enhancement of corticospinal excitability,
whereas cathodal stimulation produced a reduction. These changes in excitability were indexed by changes
in MEP amplitude. More interestingly, tDCS modulated the cortical reactivity, which is the neuronal activity
evoked by TMS, in a polarity-dependent and site-specific manner. Cortical reactivity increased after anodal
stimulation over the left M1, whereas it decreased with cathodal stimulation. These effects were partially
present also at long term evaluation.
No polarity-specific effect was found either on behavioral measures or on oscillatory brain activity. The latter
showed a general increase in the power density of low frequency oscillations (theta and alpha) at both stimulation
polarities.
Our results suggest that tDCS is able to modulate motor cortical reactivity in a polarity-specific manner, inducing
a complex pattern of direct and indirect cortical activations or inhibitions of the motor system-related network,
which might be related to changes in synaptic efficacy of the motor cortex.
Tipologia CRIS:
1.1 Articolo in rivista
Elenco autori:
M. C., Pellicciari; Brignani, Debora; Miniussi, Carlo
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