Plasticity Induced by Intermittent Theta Burst Stimulation in Bilateral Motor Cortices Is Not Altered in Older Adults

Abstract

Numerous studies have reported that plasticity induced in the motor cortex by transcranial magnetic stimulation (TMS) is attenuated in older adults. Those investigations, however, have focused solely on the stimulated hemisphere. Compared to young adults, older adults exhibit more widespread activity across bilateral motor cortices during the performance of unilateral motor tasks, suggesting that the manifestation of plasticity might also be altered. To address this question, twenty young (<35 years old) and older adults (>65 years) underwent intermittent theta burst stimulation (iTBS) whilst attending to the hand targeted by the plasticity-inducing procedure. The amplitude of motor evoked potentials (MEPs) elicited by single pulse TMS was used to quantify cortical excitability before and after iTBS. Individual responses to iTBS were highly variable, with half the participants showing an unexpected decrease in cortical excitability. Contrary to predictions, however, there were no age-related differences in the magnitude or manifestation of plasticity across bilateral motor cortices. The findings suggest that advancing age does not influence the capacity for, or manifestation of, plasticity induced by iTBS.

Intermittent theta-burst stimulation induces correlated changes in cortical and corticospinal excitability in healthy older subjects

“…The effect of iTBS on MEP has not been shown to be altered in healthy older adults (Dickins et al, 2015), though Freitas et al (2011) did find advancing age was associated with a reduced effect of cTBS. To our knowledge, no study has explored the relationship between age and TBS effects on TEPs, though several studies have looked at rs-EEG measures in older adults.…”

Intermittent Theta-Burst Transcranial Magnetic Stimulation Alters Electrical Properties of Fast-Spiking Neocortical Interneurons in an Age-Dependent Fashion

“…A couple of studies—including the use of TMS—indicate that cortical excitability and plasticity change with age accompanied by changes in the impact of inhibitory systems (Rogasch et al, 2009 ; Todd et al, 2010 ; Bashir et al, 2014 ). A recent study using iTBS, however, showed no clear age-dependent variations but a high variability of TMS effects in general (Dickins et al, 2015 ). Besides general processes of cellular aging, experience-dependent changes in network wiring strategies are discussed as contributing factors (e.g., Bernard and Seidler, 2012 ).…”

Anodal Direct Current Stimulation of the Cerebellum Reduces Cerebellar Brain Inhibition but Does Not Influence Afferent Input from the Hand or Face in Healthy Adults

“…Other studies have found that TMS measures can be reliably obtained in elderly populations [38], with little adverse side effects [39,40]. Moreover, non-invasive brain stimulation is able to promote plasticity in the older brain [41].…”