The Neural Circuitry of Motion as it Relates to Parkinson’s

News Brief by Lushna Mehra

 

   Two new studies have been published by members of the Gladstone Institutes that focus on the neural circuitry that controls motion. The basal ganglia are structures in the brain that act as the center of motion, rewards, and learning. Those with Parkinson’s disease often have lowered levels of dopamine in the basal ganglia, such that the two pathways, direct  (go) and indirect (stop), have imbalances that hinder proper walking. The first study, published in Neuron and led by Anatol Kreitzer, found that lower levels of dopamine result in miscommunication between the basal ganglia and the thalamus, which delivers sensory input to the brain.  When these pathways were imbalanced in mouse models, it was determined that blocking the connection between the basal ganglia and thalamus allowed for normal walking behavior to resume. This finding underscores the thalamus as a major player in the role of Parkinson’s and related movement suppression. The second study, published in Cell, focused on understanding the particular mechanism behind walking and how it is inhibited in Parkinson’s. It stated that the pathways in the basal ganglia control nerve cells and, specifically, that when the neurochemical glutamate is released in the direct pathway, motion occurs. Using mice models, the scientists confirmed that the direct pathway activates glutamate, allowing mice to run, and the indirect pathway inhibits it, causing mice to stop movement. As such, the researchers found that neurons in the brainstem, particularly the presence of glutamate, can trump basal ganglia signals such that if glutamate neurons are on, the mouse moves despite the indirect pathway, which inhibits movement, being off.  Further knowledge on the particular circuitry of motion in a typical human versus one with Parkinson’s would be essential in understanding how to develop future Parkinson’s treatments.

Gladstone Institutes. "Treating Parkinson's disease by solving the mysteries of movement:  Scientists discover a brain circuit that controls walking and identify a new target for treating  Parkinson's disease." ScienceDaily. ScienceDaily, 28 January 2016.  <www.sciencedaily.com/releases/2016/01/160128155004.htm>.