Combining functional imaging with brain stimulation in Parkinson's disease.

Brain stimulation techniques such as deep brain stimulation (DBS) and transcranial magnetic stimulation (TMS) constitute promising clinical and research tools to investigate neural mechanisms underlying neurological and psychiatric diseases. They have enormous potential in modifying brain activity and subsequent function. However, it is still a matter of debate how either of these stimulation approaches operates to produce the clinical outcomes observed in patients. The combination of these techniques with functional neuroimaging is contributing significantly to disentangle the mechanisms through which brain stimulation affects neuronal activity and related networks. In the present review we outline the research done to date on the effects of DBS and TMS on motor, cognition and behaviour in Parkinson's disease (PD) with particular emphasis on neuroimaging.