Functional Magnetic Resonance Imaging

Parkinsonism exhibits a combination of six important features namely tremor at rest, rigidity, gait disturbances, bradykinesia, stooped posture and freezing. Parkinsonism is represented by neurological disorders such as Parkinson’s disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). Investigation of neurological correlates for motor, memory and speech becomes essential as patients exhibit tremor, memory deficits and hampered speech. Postmortem is still considered to be the golden standard for differentiation of PD from MSA and PSP, however this provides information of end stage patients, and does not help in assessment of brain function across various stages of disease. Functional magnetic resonance imaging (fMRI) is a recently developed neuroimaging technique which has enabled the better understanding of the brain structure and function at various stages of disease on the basis of structural and/or physiological parameters. Using carefully designed task based experiments; it is now possible to assign certain brain areas to specific movements (motor), sensory perceptions (somatic, visual and auditory) and functions such as memory, mood and attention (cognitive); using haemoglobin as an endogenous contrast agent. fMRI signal also called blood oxygen level dependent (BOLD), relies on the changes in concentration of deoxyhaemoglobin associated with an increase in blood flow to active regions of the brain during an active task.