Exploring neuroplasticity through transcranial magnetic stimulation: neurocognitive mechanisms and future treatment potential

Intermittent theta burst stimulation (iTBS) is a form of excitatory, high-frequency repetitive transcranial magnetic stimulation (rTMS). When applied to the dorsolateral prefrontal cortex (DLPFC), iTBS appears to improve cognitive and neural functioning in individuals with compromised cognition associated with age-related decline or neurodegenerative diseases. This protocol may have the potential to improve cognition in other conditions such as the ‘brain fog’ in long COVID (LC). The specific cognitive functions influenced by iTBS, underlying neural mechanisms and optimal stimulation parameters are poorly understood.
The aim of this thesis was to investigate the effects of iTBS on neuroplasticity, specifically on cognitive performance and neural activity to ultimately assess the efficacy of iTBS as a potential intervention for cognitive decline. The thesis employed a mixed methods approach, utilising neuroimaging, eye-tracking and qualitative methods to address this aim.
Chapter 2 found that previous studies using high-frequency rTMS protocols, including iTBS, can have significant improvements in global cognitive function in people with age-related neurodegenerative disease. Chapter 3 found that iTBS of the left-DLPFC induces significant excitatory effects in the contralateral hemisphere during stimulation. Following this results in Chapters 4 and 5 indicated that iTBS may have significant beneficial, age-dependant effects on working memory and attention and the neural efficiency of DLPFC. Lived-experience was explored in Chapter 6 showing cognitive symptoms are prevalent in LC, with life-altering effects on daily activities, cognitive and psychological functioning. The findings in Chapter 7 revealed that more support and research is needed for people with LC including the development of treatments such as iTBS.
ITBS applied to the DLPFC influences neuroplasticity by inducing excitatory effects during stimulation with enhanced neural efficiency and improved cognitive performance after stimulation. The potential for iTBS to be used for cognitive decline in clinical populations should be explored in future research.