Mrs Mona Malekahmad1, Prof Shapour Juberzadeh1, Dr Ash Frazer1, Dr Maryam Zoghi2
1Monash University, Frankston, Australia, 2Federation University, Ballarat, Australia
Biography:
Mona Malekahmad has been an experienced neuro-clinical psychologist for 15 years. She is an expert in the diagnosis and treatment of neuropsychological diseases, and now works in neuroscience. She is interested in developing novel, safe, and non-invasive brain stimulation techniques to regulate neural network connections. Thus, as part of her PhD at Monash University, she investigates the effects of transcranial pulsed current stimulation (tPCS) on neuro-modulation and neuroplasticity. Her research focuses on the underlying mechanisms of tPCS, demonstrating its potential as an alternative treatment for neurodegenerative diseases and other clinical conditions.
Abstract:
The delta-gamma range anodal transcranial pulsed current stimulation (a-tPCS) effects on corticospinal excitability (CSE) and cortico-cortical excitability (CCE) remain unexplored. This study examined the impact of a-tPCS at 0.5, 1, 3, 5, 10, 25, and 80Hz on CSE and CCE biomarkers, as indices of underlying inhibitory/facilitatory mechanisms contributing to CSE changes, also potential stimulation-related side-effects.
Eighteen healthy participants volunteered in a double-blinded, randomized, counterbalanced crossover trial. Each completed a 20-minute session of 2mA a-tPCS at 0.5, 1, 3, 5, 10, 25, or 80Hz, with a minimum 48-hour washout between sessions. The single-pulse transcranial magnetic stimulation (TMS) assessed CSE, while paired-pulse TMS measured inhibitory/facilitatory mechanisms, including short-interval intracortical inhibition (SICI), long-interval intracortical inhibition (LICI), and intracortical facilitation (ICF) over the primary motor cortex (M1) pre- and post-stimulation.
Results significantly (p<0.05) indicated that at ≥1Hz frequencies enhanced CSE, while frequencies <1Hz decreased CSE. These changes observed at 1Hz (31%), 5Hz (35.19%), 10Hz (64.58%), and 25Hz (44.82%) were associated with increased ICF. However, the increase at 80Hz (27.66%) was associated with decreasing SICI. The CSE reduction at 0.5Hz (-18.40%) was associated with increased SICI. Mild side-effects were reported across all frequencies, while 0.5 and 80Hz did not induce phosphenes.
These findings suggest that increased CSE at ≥1Hz induce temporal summation via glutamate activation, whereas 80Hz engages counter-regulatory GABAergic mechanisms. Also, at <1Hz exert inhibitory effects by increasing GABA. Mild side-effects were reported during stimulation.
This study may guide the optimization of neuromodulation therapies by refining stimulation parameters to enhance efficacy while reducing side-effects.