The Dual Nature of Brain Changes in Parkinson’s Disease
We publish today in Progress in Neurobiology another advance in the fight against Parkinson’s disease.
We demonstrate with Alex Wiesman, who led the study, and colleagues at The Neuro (Montreal Neurological Institute-Hospital) that the slowing of brain activity, which so far has been systematically interpreted as an adverse effect of pathology, can also be a sign of compensatory activity that preserves cognitive functions.
It all depends where slowing happens in the brain!
We leveraged time-resolved brain imaging and a diverse cohort of patients and healthy controls to demonstrate this effect. We are immensely grateful for the participation of the patient volunteers from the Quebec Parkinson’s Network in this study.
Key Findings
Cortical Slowing in Parkinson’s: Patients exhibit a slowdown in cortical neurophysiology, impacting both rhythmic and arrhythmic brain functions.
Frontal Cortex as a Compensatory Hub: Contrary to expectations, we found that slowing of activity in the frontal cortex aligns with preserved motor and cognitive abilities, suggesting a compensatory role.
Parietal Impact: Symmetrically to our findings in frontal regions, we also discovered that slowing of activity in superior parietal regions are associated with more severe clinical impairments. This pattern from slow/parietal to slow/frontal forms a gradient across the cortex from adverse to compensatory roles of slowed brain activity.
Individual Sensitivity: The slowdown gradient is sensitive to individual clinical profiles, considering factors such as drug regimens and symptom laterality. It aligns with neurotransmitter systems relevant to Parkinson’s.
In-Depth Insights
Navigating Parkinson’s Complexity
Parkinson's disease brings about motor and cognitive declines due to dopamine-related neuron degeneration. Understanding the neurophysiological changes caused by the disease requires untangling the complex interplay between compensatory and adverse effects of these changes.
Spectral Insight: Frequency Dynamics
In Parkinson, beta-band activity (~30Hz in the human brain) highlights cortico-basal ganglia circuit hypersynchrony. In parallel, there is also heightened low-frequency activity and reduced high-frequency power, indicating a hypothesized global brain slowdown in patients.
A Sagittal Shift, from Compensation to Impairment
We mapped this cortical slowdown in patients, which exposed a sagittal gradient in the role of these dynamical changes in the disease natural history, highlighting a shift from functional compensation to impairment along the cortex. This posterior-to-anterior (aka sagittal) change adds a new layer to our understanding of Parkinson’s clinical landscape.
Connecting the Dots Between Local Neurophysiological Changes
Beyond neurophysiological slowdown, our study explores its impact on functional connectivity between brain regions. This broader view sheds light on intricate neurophysiological signaling slowdowns across the brain networks of Parkinson’s patients.
Take-home
In summary, we believe our research not only unravels neurophysiological changes in Parkinson’s but challenges existing ideas, offering a clearer understanding of the complexities of this disease.
The article is in free, open access at the journal.