- 作者：M. Christova ; D. Rafolt ; S. Golaszewski ; E. Gallasch
- 刊名：Clinical Neurophysiology
- 出版年：2013
- 出版时间：October, 2013
- 年：2013
- 卷：124
- 期：10
- 页码：e139
- 全文大小：36 K
Question
Weak anodal tDCS applied to the primary motor cortex during motor learning is known to increase synaptic activity in specific cortical areas involved in learning and thus to improve motor performance and memory formation. According to the rules of homeostatic metaplasticity (Ziemann and Siebner, 2008) it has been proposed that decrease of the threshold for induction of synaptic plasticity by experimental lowering the neuronal activity before practice may also facilitate learning. The study aimed to examine if anodal transcranial direct current stimulation (atDCS) applied during learning preconditioned by cathodal tDCS (ctDCS) proves to be more effective then atDCS alone in order to boost performance gains and to extend retention of motor memory.Methods
To prove this hypothesis three matched study groups (n = 12) were recruited: a group receiving 15 min sham preconditioning stimulation before learning and atDCS during learning (atDCS), a group receiving 15 min preconditioning ctDCS before learning and atDCS during learning (c/atDCS) and a group receiving sham stimulation (sham). Grooved pegboard test (GPT) was employed as a learning paradigm. For evaluation of the learning and tDCS-induced effects, behavioural measures and transcranial magnetic stimulation (TMS) assessments were considered. Time to complete the GPT was evaluated across four blocks; task retention was tested after two weeks. Cortical excitability changes were assessed with single and paired-pulse TMS at baseline (T0), post preconditioning stimulation (T1), post training (T2) and 60 min post training (T3).
Results
Anodal tDCS applied to the motor cortex during execution of the grooved pegboard test improved significantly motor performance compared to the sham group. This effect was even enhanced when the motor cortex was preconditioned with ctDCS. Importantly in this case also the motor memory was improved as tested after two weeks. The observed effects correlated with changes in motor cortical excitability. Application of ctDCS induced decrease in motor evoked potential (MEP) amplitude and intracortical facilitation (ICF) and increase in intracortical inhibition (SICI). However application of atDCS resulted in increased MEP amplitude and ICF and decreased SICI. When atDCS was preceeded by 15 min ctDCS the facilitatory effects were retained for 1 h.
Conclusion
Decreased neuronal activity by ctDCS increase subsequent facilitation of learning-dependent plasticity resulting in improved performance gains and retention. The results provide better understanding on the ability to modulate motor learning and memory with non-invasive brain stimulation through gating and homeostatic metaplasticity. This holds potential for clinical applications, specifically for the development of learning-stimulation protocols.