Contribution of TMS and TMS-EEG to the Understanding of Mechanisms Underlying Physiological Brain Aging

Abstract

In the human brain, aging is characterized by progressive neuronal loss, leading to disruption of synapses and to a degree of failure in neurotransmission. However, there is increasing evidence to support the notion that the aged brain has a remarkable ability to reorganize itself, with the aim of preserving its physiological activity. It is important to develop objective markers able to characterize the biological processes underlying brain aging in the intact human, and to distinguish them from brain degeneration associated with many neurological diseases. Transcranial magnetic stimulation (TMS), coupled with electromyography or electroencephalography (EEG), is particularly suited to this aim, due to the functional nature of the information provided, and thanks to the ease with which it can be integrated with behavioral manipulation. In this review, we aimed to provide up to date information about the role of TMS and TMS-EEG in the investigation of brain aging. In particular, we focused on data about cortical excitability, connectivity and plasticity, obtained by using readouts such as motor evoked potentials and transcranial evoked potentials. Overall, findings in the literature support an important potential contribution of TMS to the understanding of the mechanisms underlying normal brain aging. Further studies are needed to expand the current body of information and to assess the applicability of TMS findings in the clinical setting.

Cognitive deficit in post-acute COVID-19: an opportunity for EEG evaluation?

“…Taken together, these findings suggest a possible effect of COVID-19 syndrome on cortical transmission which might be objectively measured by neurophysiological techniques. Indeed, the association between cortical excitability measured by TMS and brain oscillatory activity measured by EEG has been reported in physiological brain aging and in different neurological diseases, including epilepsy and MCI [29][30][31].…”

Barriers to Enrollment in Post-Stroke Brain Stimulation in a Racially and Ethnically Diverse Population

“…Increasing the age limit of enrollment may increase participation in the study, in particular of W patients and of women, as these groups presented at a later age with stroke. Brain plasticity is diminishing with advancing age 41,42 ; however, evidence for life-long neuroplasticity is mounting, 43,44 suggesting that older patients might also benefit from an effective non-invasive stimulation. Enrolling patients with hemorrhagic strokes and severe UE weakness could preferentially enhance the participation of men.…”

Long-interval intracortical inhibition in primary motor cortex related to working memory in middle-aged adults

“…Next, 120 paired-pulse TMS stimuli were delivered to the left-M1 at random intervals between 3 and 6 s. The intensities of both pulses were applied at 120% of RMT, and the ISI was 100 ms, selecting this interval because it was reportedly optimal ( Sanger et al, 2001 ), and previous research has suggested age-related changes at it ( McGinley et al, 2010 ; Opie et al, 2015 , 2018 ). From this stimulation, LICI was calculated using the following formula ( Guerra et al, 2021 ):…”

“…BBHI, Barcelona Brain Health Initiative; NP, Neuropsychological assessment; MRI, Magnetic resonance imaging; RMT, Resting Motor Threshold. 10.3389/fpsyg.2022.998062 Frontiers in Psychology 04 frontiersin.org stimulation, LICI was calculated using the following formula (Guerra et al, 2021):…”

“…Long-Interval Intracortical Inhibition (LICI), where two suprathreshold stimuli separated by an interstimulus interval (ISI) between 50 and 200 ms are applied, has been used to study cortical inhibition ( Valls-Solé et al, 1992 ; Nakamura et al, 1997 ) and reflects the activity of GABA-B receptors ( McDonnell et al, 2006 ; Opie et al, 2017 ). While many studies have shown that RMT and LICI offer valuable biological markers in different neurological disorders ( Fatih et al, 2021 ; Guerra et al, 2021 ; Mimura et al, 2021 ; Versace et al, 2021 ), only a few have explored their association with brain health and cognitive performance in healthy, cognitive-unimpaired, middle-aged adults, and how biological sex affects the results ( Schicktanz et al, 2014 ; Akilan et al, 2020 ).…”