Parksinson’s disease isn’t just about tremors or difficulty moving; it can also impact sleep, sense of smell, digestion, and cognitive functions.
According to a recent study published in *Nature*, the disease seems to disrupt a communication network in the brain that links physical movements and mental processes.
One brain scientist, Hesheng Liu from Peking University, described the situation as if a tunnel is blocked, causing all traffic to halt. This aligns with increasing evidence suggesting that Parkinson’s should be viewed as a disorder of the brain’s network rather than one confined to specific movement-controlling areas, adds Peter Strick from the University of Pittsburgh, who wasn’t part of the study.
Various neurodegenerative diseases affect distinct brain networks. For instance, Alzheimer’s typically damages the default mode network, which is crucial for memory and self-awareness, while ALS mainly targets the motor system network responsible for movement.
With roughly 1 million people affected by Parkinson’s in the U.S., understanding the related brain network could change treatment methods significantly.
A puzzle piece found?
Symptoms in Parkinson’s can vary surprisingly, leading to confusion about their origins.
For instance, some patients who usually struggle to stand may unexpectedly leap during emergencies, while those who can still walk might freeze mid-conversation. Liu points out that these movement challenges are linked not only to motor functions but also to circuits governing thought and emotion.
This connection had puzzled scientists for many years until a team at WashU Medicine in St. Louis identified a brain network—termed the somato-cognitive action network (SCAN)—believed to connect movement and cognition.
Using MRI data from over 800 individuals, Liu’s team compared SCAN networks in healthy individuals and those with Parkinson’s. They discovered that connections in patients were unusually strong between SCAN and affected brain areas, which led to a signal traffic jam. This jam meant that communication among areas was hindered, rather than improved.
Addressing the network
Liu’s team then researched how Parkinson’s treatment influences the SCAN network, particularly during deep brain stimulation treatments, which involve delivering electrical pulses to specific brain regions. They noted that activating the stimulator instantly reduced connectivity, restoring normal signal flow.
Further investigations into other treatments, including levodopa, transcranial magnetic stimulation, and focused ultrasound, showed all these therapies impact the same brain circuitry, producing surprisingly similar effects.
This research is part of a shift in how Parkinson’s is perceived. Strick emphasizes the outdated view of Parkinson’s strictly as a movement disorder, noting that the condition affects various systems.
Parkinson’s patients frequently report symptoms beyond just motor issues, like slurred speech and shuffling gaits. They may also experience chronic constipation, diminished smell, sleep problems, memory gaps, and fatigue, which involve brain systems unrelated to movement.
Not just intoxication
This unpredictable combination of symptoms can lead to misinterpretations that feel stigmatizing. For example, Strick recalls one patient who would fall suddenly due to a drop in blood pressure, leading others to assume he was inebriated. However, he felt relieved when receiving a proper diagnosis that clarified his situation.
Strick believes the new findings help explain such odd symptoms, as the SCAN network includes regions that usually manage involuntary functions like heart rate and digestion, among others.
Although current Parkinson’s treatments don’t address these non-motor issues, Liu suggests future therapies might by targeting specific areas within the SCAN network.
