Age-related changes in cortical connectivity influence the neuromodulatory effects of transcranial electrical stimulation

Transcranial Random Noise Stimulation Modulates Neural Processing of Sensory and Motor Circuits, from Potential Cellular Mechanisms to Behavior: A Scoping Review

“…It is currently unclear whether these variable result patterns reflect small or inconsistent effects induced by tRNS or depend on participant-specific determinants. For example, the after-effects following tRNS were suggested to vary depending on interindividual differences such as age ( Fertonani et al, 2019 ) or a person’s susceptibility to placebo effects ( Kortuem et al, 2019 ), but probably independent of the BDNF gene polymorphism ( Antal et al, 2010 ). Long-term modulation of CSE with tRNS was suggested to be task-dependent and specific to the underlying brain state ( Chaieb et al, 2009 ; Saiote et al, 2013 ; Jooss et al, 2019 ; Qi et al, 2019 ).…”

The Effect of Transcranial Random Noise Stimulation on Cognitive Training Outcome in Healthy Aging

“…This effect could be explained via its main mechanism, stochastic resonance, which can mitigate the age-dependent increase in neuronal noise (50). However, other studies have suggested that tRNS might be less effective in older than younger adults (22). We used a scientifically rigorous double-blind, sham-controlled, randomized study design to investigate the questions put forth with as minimal experimental bias as possible and confirmed successful blinding of the subjects.…”

“…However, the rather large variability in response to brain stimulation is also increasingly investigated and discussed in young healthy populations (76,77). Recent studies demonstrated that by using a combination of neurophysiological and neuroimaging methods with neurostimulation we can shed light on interindividual mechanisms that drive response variability (16,22,24,46,78,79) and use this knowledge to improve stimulation efficacy (80). Associated with this, we also need to reconsider the practice of investigating questions in another than the target population.…”

“…However, these results have not been universally supported, with others finding no clear difference between the effects of tDCS and tRNS on motor cortex excitability (20). tRNS might lead to more widespread effects via stochastic resonance (21) and the aging brain might react differently to tRNS due to the activation of broader networks (22). Age appears to be associated with more beneficial outcomes in neurostimulation in some studies (23,24).…”

“…Moreover, a recent study in juvenile mice revealed that chronic tRNS over the prefrontal cortex, with similar parameters to what has been used in atypically developing children (48), reduced GABAergic activity (49). Single sessions of tRNS showed promise in modulating cognitive functions in aging (22,28,50). However, to date, the potential of tRNS as an effective cognitive enhancer in older adults remains to be shown.…”