Scientists develop new method to detect motor disorders using 3D objects

Researchers at HSE University have developed a new methodological approach to studying motor planning and execution. By using 3D-printed objects and an infrared tracking system, they demonstrated that the brain initiates the planning process even before movement begins. This approach may eventually aid in the assessment and treatment of patients with neurodegenerative diseases such as Parkinson’s. The paper has been published in Frontiers in Human Neuroscience.

When a person picks up a cup or fastens a button, the brain plans the movement in advance—a process known as motor planning. This is especially important for complex actions, such as when an object must not only be lifted but also rotated. In patients with stroke or Parkinson’s disease, this mechanism is often impaired, making it essential to understand its structure for effective rehabilitation.

In earlier studies, researchers relied on reactions to visual stimuli, EEG, or MRI to investigate motor planning. However, these methods could not precisely distinguish between the planning phase and the execution of movement. Moreover, most experiments involved familiar objects, making it difficult to rule out the influence of habits and prior associations.

Scientists at the HSE Centre for Cognition and Decision Making have developed a new methodological framework for studying motor planning in the brain. In the experiment, 21 participants performed a series of tasks involving the grasping and placement of 3D-printed objects. Each of the four objects was an abstract geometric shape, unrelated to everyday items, thereby eliminating the influence of habit. The task required participants to grasp an object, rotate it if necessary, and place it precisely onto a corresponding cardboard plate.

In the experiment, four rotation angles were tested: 0°, 90°, 180°, and 270°. High-precision motion tracking was carried out using infrared cameras. Each movement was segmented into phases, from the moment the occlusion glasses opened to the completion of object placement. This approach enabled the researchers to examine in detail how motion parameters change as task complexity increases.

The study found that rotation had a significant impact on motion planning: movements involving rotation had longer initiation times, larger grasp apertures, and longer wrist trajectories compared to non-rotated movements. Symmetrical 180° rotations were executed faster than asymmetrical 90° and 270° rotations. These results indicate that not only task complexity but also movement geometry influences planning. Thus, motor planning is not merely a simple response to a stimulus but a distinct movement phase shaped by the demands of the task.

The developed methodological framework may prove valuable not only for basic research but also for clinical practice. Clearly separating the planning and execution phases can lead to more accurate diagnoses and more effective rehabilitation for patients with motor disorders after stroke or other neurological conditions. 'The infrared motion tracking system fits into a portable case and can be used in clinics, sports science, or field research. Most importantly, it enables the detection of subtle delays in motor planning, which may serve as early indicators of neurological disorders,' explains Matteo Feurra, Leading Research Fellow at the HSE Centre for Cognition and Decision Making and one of the authors of the study.

The study was carried out within the framework of the HSE Basic Research Programme.