Research techniques: Transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) is a non-invasive method of changing neural excitability. In 1985, the first modern TMS device was built and tested by Anthony Barker and colleagues in Sheffield. Repetitive TMS (rTMS) refers to the application of regular TMS pulses to a scalp position. rTMS at low frequency (≤ 1-Hz) decreases neuronal excitability of the stimulated brain area, whereas rTMS at high frequency ranges (> 5-Hz) increases neuronal excitability. As rTMS induces changes in brain function extending beyond the immediate stimulation period, it has been considered as a potential treatment for a variety of psychiatric disorders, as well as a useful tool for investigating brain function in healthy volunteers. For example, we have shown that transient cerebellar stimulation can differently affect the ability to estimate time intervals below and above a duration of 1 second (Lee et al., 2007, Journal of Cognitive Neuroscience).

We are currently conducting a randomized, controlled trial to investigate whether TMS is effective in treating schizophrenia patients with severe negative symptoms. We are using a powerful rTMS protocol, (referred to as "Theta Burst Stimulation") which involves the use of a train of 3 closely spaced pulses of TMS at 50 Hz delivered at 5Hz (which falls within the theta frequency range of 4-8 Hz). The effect of this method has been shown to last significantly longer than that of conventional rTMS. The primary outcome measure of this study is brain activity during fMRI. Secondary outcome measures will include symptom severity, cognitive and psychosocial functioning. This study is being conducted in collaboration with Professor Barker (Medical Physics) and Dr Iain Wilkinson (Radiology).