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Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex
Sangeetha Madhavan1, Aishwarya Sriraman2, Sally Freels3
1Department of Physical Therapy, University of Illinois at Chicago, 1919 W. Taylor St., Chicago, IL 60612, USA. smadhava@uic.edu.
Brain Sciences
|July 30, 2016
Summary
This study investigated the reliability and variability of transcranial direct current stimulation (tDCS) for lower limb motor control. Findings indicate that measurement methods influence tDCS reliability, and high reliability doesn't guarantee clinical effectiveness.
Area of Science:
- Neuroscience
- Motor Control Research
- Rehabilitation Technologies
Background:
- Transcranial direct current stimulation (tDCS) shows potential for enhancing motor function.
- Concerns exist regarding the reliability and variability of tDCS-induced neuromodulation.
Purpose of the Study:
- To assess the test-retest reliability and inter-individual variability of tDCS applied to the lower limb primary motor cortex (M1).
- To explore the relationship between transcranial magnetic stimulation (TMS)-derived measures and tDCS effects.
Main Methods:
- Fifteen healthy participants underwent anodal tDCS of lower limb M1 during a motor task and at rest, with each condition tested twice.
- Corticomotor excitability of the tibialis anterior muscle was measured using TMS before and after tDCS.
- Intraclass correlation coefficients (ICC) and variance component analyses evaluated reliability and variability.
Main Results:
- tDCS during a motor task significantly increased corticomotor excitability at 140% active motor threshold (AMT) and for recruitment curve slopes.
- Test-retest reliability (ICC) ranged from 0.6-0.9, with higher values at greater TMS intensities.
- Inter-individual variability accounted for 34% of the observed variance.
Conclusions:
- The choice of TMS-based measurement impacts the perceived reliability and variability of tDCS effects.
- High reliability and low variability do not automatically confirm clinical efficacy, as some individuals showed minimal response.
