Facilitatory non-invasive brain stimulation in older adults: the effect of stimulation type and duration on the induction of motor cortex plasticity

Abstract

36Despite holding significant promise for counteracting the deleterious effects of ageing on 37 cognitive and motor function, little is known of the effects of facilitatory non-invasive brain 38 stimulation (NBS) techniques on corticospinal excitability (CSE) in older adults. 40Thirty-three older adults (≥ 60 years) participated in four NBS sessions on separate days ("responders", n = 10), 20 min atDCS resulted in longer lasting CSE facilitation than 10 min. 50No such difference was observed between the two iTBS protocols.

Can genetic polymorphisms predict response variability to anodal transcranial direct current stimulation of the primary motor cortex?

“…In addition to reporting overall significant increases in CSE following a-tDCS, the reported subgroups of individuals based on subjects exceeded a pre-determined threshold was similar to previous studies. Based on the pre-determined threshold of sham-tDCS baseline MEP SD (Ammann et al, 2017), 43% of individuals responded as expected with increases in CSE, similar to that of previous subgrouping studies ranging from 33-74% (Ammann et al, 2017;Chew et al, 2015;López-Alonso et al, 2014Puri et al, 2015Puri et al, , 2016Strube et al, 2015Strube et al, , 2016Tremblay et al, 2016;Wiethoff et al, 2014). As a point of difference to the majority of previous large-scale subgrouping studies, by setting the threshold at the SD of CSE at baseline in the sham-tDCS condition, this subgrouping technique in-part accounted for the inherent variation that may occur when measuring changes in CSE via TMS-evoked MEPs and that is specific to the current cohort of participating individuals.…”

“…As a point of difference to the majority of previous large-scale subgrouping studies, by setting the threshold at the SD of CSE at baseline in the sham-tDCS condition, this subgrouping technique in-part accounted for the inherent variation that may occur when measuring changes in CSE via TMS-evoked MEPs and that is specific to the current cohort of participating individuals. If the inherent variation, as indicated by the SD in baseline conditions, is greater than 10% or 20%, as with this current study, and it is not accounted for, then it is unclear whether categorisation as a responder based on a 10% or 20% threshold as previously utilised (Chew et al, 2015;López-Alonso et al, 2014Puri et al, 2015Puri et al, , 2016Strube et al, 2016;Wiethoff et al, 2014) reflects a true increase in CSE or just the inherent variability of TMS-evoked…”

“…'non-responders'). This dichotomy, termed inter-individual variability, extends to other NIBS protocols including Theta Burst Stimulation (TBS) (Goldsworthy et al, 2016;Hamada et al, 2013;Hinder et al, 2014;López-Alonso et al, 2014Nettekoven et al, 2015;Puri et al, 2016;Vallence et al, 2015) and Paired Associative Stimulation (Labruna et al, 2016;López-Alonso et al, 2014F. Müller-Dahlhaus et al, 2015;J.…”

“…When keeping stimulus parameters consistent with standard protocol of 1mA current intensity and 10-13 minutes stimulus duration (M. A. Nitsche & Paulus, 2000), responder rates vary from 20-60% (Ammann et al, 2017;Chew et al, 2015;López-Alonso et al, 2014;Puri et al, 2016;Strube et al, 2015Strube et al, , 2016Tremblay et al, 2016).…”

Preconditioning tDCS facilitates subsequent tDCS effect on skill acquisition in older adults

“…At neurophysiological level, tDCS placing anode electrode placed over M1 with the current intensity of 1.5 mA increases MEP amplitude in young (Karok and Witney 2013, Tremblay et al 2013a, Williams et al 2013) and older adults (Puri et al 2016, Puri et al 2015.…”