Amygdala damage linked to Parkinson’s vision problems: Study
Analysis maps brain structures, eye structures, vision tests in patients, controls
Damage to a part of the brain called the amygdala plays a key role in vision problems for people with Parkinson’s disease, a study suggested.
Vision problems are relatively common as people get older. In typical aging, vision problems arise because of issues in the eyes and vision-processing pathways, while the amygdala is minimally affected, the researchers noted, suggesting amygdala changes are a unique feature of vision problems related to Parkinson’s.
The researchers combined detailed analyses of brain structures, eye structures, and vision tests to look for specific parts of the brain that are associated with vision issues in Parkinson’s patients. The study looked at data from 42 Parkinson’s patients, with data from 29 people without the disease used for comparison.
The study, “Amygdala Neurodegeneration: A Key Driver of Visual Dysfunction in Parkinson’s Disease,” was published in the Annals of Clinical and Translational Neurology.
Vision problems are a common nonmotor symptom of Parkinson’s, often developing early in the course of the disease. Most research into vision problems in Parkinson’s has looked at how the disease affects the eyes themselves. Data have suggested that Parkinson’s affects the eyes, which likely contributes to vision problems. But vision problems in Parkinson’s aren’t fully explained by damage to the eyes, which implies that the disease may also cause issues in parts of the brain that are responsible for processing visual information.
‘Common denominator’ for Parkinson’s vision problems
The study found Parkinson’s patients showed some signs of damage in parts of the brain that are known to be important for controlling vision. However, most of the vision-related damage was centered on the amygdala, an almond-shaped brain region that’s best known its role in regulating emotion and fight-or-flight instincts.
Normally, the amygdala is integrally connected to other parts of the brain that are important for processing vision. These connections help people make quick emotional judgements about things they see. But data suggest that these connections become disrupted in Parkinson’s, contributing to vision issues.
“Our findings highlight amygdala atrophy [shrinkage] as the common denominator across all visual domains explored,” the researchers wrote. That “underscores the amygdala’s central role in [Parkinson’s]-related visual impairments, providing a unifying neuroanatomical basis for deficits spanning diverse visual functions,” they wrote.
Further analyses indicated that vision-related brain damage occurs in two main phases in Parkinson’s. First, there is damage to the amygdala, which causes disruptions in the neurological circuits that the brain normally uses to make sense of what the eyes see. Then, as these nerve signaling pathways become increasingly damaged, light-sensing cells in the eyes also start to deteriorate, and the combination of brain and eye damage ultimately gives rise to vision problems that people with Parkinson’s experience, distinct from vision issues in typical aging.
“This integrative model highlights the amygdala’s critical role in the progression of [Parkinson’s]-related visual dysfunction and establishes a framework for understanding its structural and functional underpinnings,” the researchers concluded.
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