Dr. Natasha Radhu, Post-doctoral Fellow
Toronto Western Research Institute (University Health Network)
Porridge for Parkinson’s (Toronto) Basic Research Fellowship: $80,000 over two years

Interactions between Motor Cortical Inhibitory and Excitatory Circuits in Parkinson’s disease

Increasingly, scientists studying the brain believe one of the reasons abnormalities and diseases develop is the result of an imbalance in two types of circuits, or processes, which regulate the flow of information among brain cells.

At the Toronto Western Research Institute, neurophysiologist Natasha Radhu uses Transcranial Magnetic Stimulation (TMS) to study those two processes – the brain’s excitatory and inhibitory circuits. She investigates whether an imbalance in the circuits in the motor cortex, the section of the brain that governs movement, is connected to Parkinson’s disease.

Transcranial Magnetic Stimulation involves using a magnetic coil to generate an electrical pulse that stimulates brain cells. Radhu and her colleagues position the coil over the motor cortex in the brain of people with Parkinson’s disease. The pulses cause the muscles of the person they are studying to twitch – twitches the researchers measure. By exciting or inhibiting the muscle twitches, the researchers can indirectly measure the excitatory and inhibitory circuits in the brain. She’s comparing the measurements from the people with Parkinson’s to those of people without the disease.

“It’s a balance of these two (circuits) which indicate healthy brain functioning,” Radhu says.

Radhu measures the degree of movement that occurs in people with Parkinson’s when TMS stimulates their motor cortex while they are on levodopa medication, and when they are off it. She’s testing her theory that when people are off medication, and experience tremors, stiffness, or freezing of gait, she will see increased activity in the excitatory circuits in the brain. At the same time, the inhibitory circuits that stop or calm the flow of information to brain cells will be less active.

Radhu believes her work will demonstrate that when the two circuits are not balanced, people with Parkinson’s disease can’t calm the rapid signals to the area of the brain that directs movement.

By studying the way levodopa affects and changes the brain, Radhu hopes to see how effective the medication is and whether it improves symptoms. She also hopes this measurement of brain activity could eventually diagnose Parkinson’s disease.

“If we’re able to say that certain medications can restore these calming mechanisms and bring the brain back to its healthy balance, we could recommend using these medications more,” she says.