Changes in Brain Architecture Tied To Poor Bimanual Coordination

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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Small-scale, or microstructural, brain alterations observed on the MRIs of people with Parkinson’s disease were associated with worse bimanual coordination, a type of complex movement, a study found.

“[D]istinct changes in microstructure cause an impediment of structures involved in attention, working memory, executive function, motor planning, motor control, and visual processing contributing to impaired bimanual coordination in Parkinson’s disease,” the researchers wrote.

The study, “Microstructural alterations predict impaired bimanual control in Parkinson’s disease,” was published in Brain Communications. 

Bimanual coordination describes situations in which a person must simultaneously control and coordinate multiple movements to perform a task, for example, using both hands to eat with a knife and fork. Such coordination is commonly impaired in Parkinson’s patients, which can significantly affect their ability to perform daily activities independently.

Communication within a network of several brain regions is needed for proper movement coordination. To enable such communication, nerve cell projections, called axons, which send messages within and between brain regions, must be healthy.

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The toxic buildup of alpha-synuclein characteristic of Parkinson’s causes cellular damage that leads to microstructural changes — small-scale changes to nerves and their support cells — that can hinder information transfer between brain regions.

Researchers in Germany investigated whether microstructural changes in the brain contribute to bimanual coordination impairments in Parkinson’s patients.

The study included 23 Parkinson’s patients and 26 older adults without Parkinson’s who served as a control group. All the participants were recruited from the Max Planck Institute for Metabolism Research and healthy controls were matched to patients for age, sex, handedness, and cognitive status. Patients’ mean age was 56. The mean age of the control group was 58.5.

All participants underwent a test of bimanual coordination. In patients, the test was performed both when on and off medication. Sitting in a chair in front of a computer screen, participants placed their fingers on a response pad with a single button for each finger. After memorizing and practicing a sequence of finger taps on one hand, they were tested on their ability to repeat the sequence while simultaneously tapping a different sequence displayed on the screen with the other hand.

Participants were advised to prioritize accuracy over speed during the task.

All the participants made more mistakes when attempting a more complex sequence. Parkinson’s patients either on or off medication made more mistakes overall than healthy controls in the task, suggesting impairments in bimanual coordination.

A specialized type of MRI, called diffusion MRI, was performed on healthy controls and patients when they were on medication to look at changes in brain architecture that might be related to these coordination impairments.

Several differences were observed between the brains of Parkinson’s patients and healthy controls.

“We found a distinct profile of microstructural changes in Parkinson’s disease replicating major findings consistent across the literature and in accordance with known Parkinson’s disease pathophysiology [disease mechanisms],” the researchers wrote.

Certain microstructural changes were predictive of poor bimanual coordination.

Specifically, changes in the brain’s white matter tracts, which contain axons that communicate within and between brain regions, showed abnormalities linked to poor coordination performance. These changes influenced the connectivity between brain regions important for executive function — skills involved in daily functioning, motor control, visual processing, attention, memory, and planning of complex behaviors.

Altered microstructure in the brain’s gray matter — containing mostly cell bodies — specifically in brain regions associated with processing sensory information and memory, was also linked to worse bimanual coordination.

“We describe a spatially distinct profile of microstructural alterations associated with poor bimanual coordination,” the researchers wrote. “Structures important for attentional networks, working memory, executive function, overall motor control and planning, as well as visual processing are affected and contribute to poor bimanual coordination in Parkinson’s disease.”