Investigating the mechanisms of non invasive brain stimulation using MRI

Many diseases of the brain share a common, core, pathology: dysfunction across both vascular and neuronal transporter mechanisms. Directly targeting these processes in-vivo can be challenging using only pharmacological means. However, the past 25 years has seen the introduction and rapid rise in the use of transcranial Direct Current Stimulation (tDCS), a non-invasive neuromodulatory technique. tDCS has some clinical efficacy: for example,  it can significantly improve mood in depression; and increase motor performance post-stroke.

But is tDCS a neuromodulator, or a neurovascular modulator? Vascular responses are ubiquitous in neuromodulation, but are in general considered epiphenomena to neuronal stimulation. Conventional theories of brain stimulation consider only neuron  polarization;  but  in vitro models with isolated glia (REF) and endothelial cells (REF) show these cell types are also affected by tDCS.

These issues may underpin tDCS’ most prevalent issue: its high intra- and inter-participant variability. A fuller understanding of the underlying mechanisms driving tDCS’ effects on brain health and behaviour would allow better evidence-based treatments to be developed: there are many appealing aspects to tDCS as a therapeutic, not limited to its simplicity, cheapness, and non-invasive nature.

The aim of this project is to combine complementary MRI approaches to map the physiological changes induced by tDCS, and to establish the optimal protocols for delivering the stimulation, with an emphasis on establishing a framework for understanding underlying neuro vs neurovascular mechanisms. Specifically, the project will investigate tDCS induced changes in: 1) regional cerebral blood flow; 2) sodium concentration; 3) blood brain barrier permeability induced by tDCS. Crucial for any future clinical role, the duration of such changes will also be determined. Supporting this, the project will explore MRI-based methods for mapping the brain’s conductivity, and compare them against the current gold standard, based on fixed conductivity values associated with white and grey matter of the brain (ref). The PhD project will take place in Cardiff University’s Brain Research Imaging Centre (CUBRIC), which hosts state-of-the-art MRI and brain stimulation equipment. The student will receive training in tDCS and MRI, and will have an active role in designing, running, and analysing the experiments. Exposure to a combination of techniques will equip them with an exceptional skillset, also providing a deep understanding of brain physiology. The supervisors have complementary expertise which will ensure the student receives appropriate support for all aspects of the study. 

Home students are UK Nationals and EU students who can satisfy UK residency requirements (students must have been in the UK for >3 years before start of course).

 As only a limited number of studentships are available across the Open School competition and a very high standard of applications is typically received, the successful applicants are likely to have a very good first degree (a First or Upper Second class BSc Honours or equivalent) and/or be distinguished by having relevant research experience.