Age-dependent non-linear neuroplastic effects of cathodal tDCS in the elderly population: a titration study.

Background: Neuromodulatory effects of transcranial direct current stimulation (tDCS) in older humans have shown heterogeneous results, possibly due to sub-optimal stimulation protocols associated with limited knowledge about optimized stimulation parameters in this age group. We systematically explored the association between the stimulation dosage of cathodal tDCS and induced after-effects on motor cortex excitability in the elderly.

Method: Thirty-nine healthy volunteers in two age groups, namely Pre-Elderly (50-65 years) and Elderly (66-80 years), participated in the study.

Exploring and optimizing the neuroplastic effects of anodal transcranial direct current stimulation over the primary motor cortex of older humans.

Background: tDCS modulates cortical plasticity and has shown potential to improve cognitive/motor functions in healthy young humans. However, age-related alterations of brain structure and functions might require an adaptation of tDCS-parameters to achieve a targeted plasticity effect in older humans and conclusions obtained from young adults might not be directly transferable to older adults. Thus, our study aimed to systematically explore the association between tDCS-parameters and induced aftereffects on motor cortical excitability to determine optimal stimulation protocols for older individuals, as well as to investigate age-related differences of motor cortex plasticity in two different age groups of older adults.

Age-related differences of motor cortex plasticity in adults: A transcranial direct current stimulation study.

Background: Cognitive, and motor performance are reduced in aging, especially with respect to acquisition of new knowledge, which is associated with a neural plasticity decline. Animal models show a reduction of long-term potentiation, but not long-term depression, in higher age. Findings in humans are more heterogeneous, with some studies showing respective deficits, but others not, or mixed results, for plasticity induced by non-invasive brain stimulation.

Effects of electrode angle-orientation on the impact of transcranial direct current stimulation on motor cortex excitability.

Background: For effects of transcranial direct current stimulation (tDCS), electrical field distribution and coverage of the target areas play a decisive role.

Methods: We explored the effect of different angle-orientations of tDCS electrodes applied over the upper limb motor cortex (M1) on motor cortex excitability in healthy volunteers. Sixteen individuals received 1 mA anodal or cathodal tDCS through 35 cm electrodes over M1 for 15 min.