Parkinson's disease has several key physical symptoms related to movement, such as stiffness, slowness of movement, tremor, and problems with walking and balance. These symptoms are partly caused by reduced activity of a brain chemical called dopamine in a deep brain region known as the basal ganglia, which helps control movement. Researchers have previously considered that certain bright spots seen on brain scans, called white matter hyperintensities, might make motor symptoms worse when they appear in the brain's outer layers. However, the effect of these bright spots in the basal ganglia was not well understood.

This study aimed to examine the connection between the amount of white matter hyperintensities in deep brain structures and the severity of motor symptoms in people with Parkinson's disease.

The study included 140 participants with Parkinson's disease. Researchers used brain scans to measure the percentage of white matter hyperintensities in the whole brain, in the four outer lobes of the brain, and in a combined deep brain region that includes the basal ganglia and a related structure called the thalamus. They then used statistical methods to test for connections between the amount of these bright spots and the participants' motor function.

The results showed that a greater amount of white matter hyperintensities in the basal ganglia and thalamus region was associated with better motor function. In contrast, the amount of these bright spots in the brain's outer lobes was not linked to worse motor symptoms. When participants were grouped by the amount of these spots in the basal ganglia and thalamus, those with the largest amount had better motor function than those with smaller amounts.

The study concluded that these spots in the basal ganglia and thalamus were connected to improved motor function. The researchers suggest that this might happen because the spots disrupt brain circuits that normally act as a "brake" on movement, which could in turn readjust the brain's signals for controlling movement. These results lead to new hypotheses about how brain circuits can be modified in Parkinson's disease and may inform future research into the disease's mechanisms and potential treatments. It is noted that because the findings show a correlation, they do not prove that the bright spots caused the better motor function.