A new study by neuroscientists at the German Primate Centre (DPZ) – Leibniz Institute for Primate Research in Göttingen shows that our brain deals with different forms of visual uncertainty during movements in different ways. Depending on which type of uncertainty is involved, this has very different effects on the planning and execution of movements in the brain. These findings could help to optimise brain-computer interfaces that, for example, help people with paralysis to control prostheses or computers with their thoughts alone (Nature Communications).
Göttingen/Germany, April 14, 2025. Scientists from the Sensorimotor Research Group at the German Primate Center Göttingen investigated the brain’s ability to make decisions during imprecise movements, which often occur under the influence of darkness or other obstacles.
This involves two pieces of information. Firstly, where an extremity, in this example the hand, is located, and the other question asked by the brain is where the hand is moving to. In an experiment with monkeys, two types of these visual uncertainties were investigated: target uncertainty and feedback uncertainty.
In the case of target uncertainty, the target of the movement was represented by several scattered objects so that it remained unclear where exactly the target was located. In feedback uncertainty, the cursor was replaced by several scattered, small objects so that it remained unclear exactly where the monkey’s own hand was located. In addition, the researchers tested the effects of feedback uncertainty while the monkeys controlled the cursor through a brain-computer interface, virtually by mere thought. In this case, only visual information is available as feedback about one’s own movement, whereas with real arm movements, the body also knows the position of the hand via other sensory systems.
The results clearly show that the brain reacts differently to uncertainty.
Target uncertainty primarily affects planning and the start of the movement. If the target was unclear, the movements were also less precise and less accurately planned.
In contrast, the impairment of movements due to feedback uncertainty was only clearly evident when the monkeys were completely dependent on visual feedback – as in the case of control using a brain-computer interface. In this case, the feedback uncertainty primarily influenced the precise execution of the movement.
The researchers also found that neuronal activity in the motor cortex reflects both target and feedback uncertainty, but that these two forms of uncertainty are processed at different times. This suggests that the brain integrates information about the target and the hand position in different phases of movement control.
Relevance for brain-computer interfaces
The findings could help to improve brain computer interfaces (BCIs). This technology enables paralyzed people, for example, to control prostheses or computers with their thoughts alone. Since users of BCIs usually rely heavily on visual feedback, as this is often all they have at their disposal, they are particularly susceptible to uncertainties in the perception of their own movement. The integration of additional sensory signals could be a promising solution. For example, vibration motors, i.e., tactile feedback, could provide users with additional information about the movement of their hand and compensate for uncertainties. The research group led by Alexander Gail is already continuing the experiments and further developing the research approach as part of the new Collaborative Research Center SFB 1690.
Lukas Amann, neuroscientist in the Sensorimotor Research Group and lead author of the study together with Virginia Casasnovas, explains: “Our results show that the brain can compensate for uncertainty when alternative sources of information are available. This is a crucial factor for improving BCIs, as users are currently often limited to visual feedback. Additional sensory stimuli could help to make the control of neuroprostheses more precise and intuitive.”
The study thus provides important insights into how the brain deals with sensory uncertainty – a basis for the further development of technologies that could help people with motor impairments.
Originalpublikation:
Amann, L.K., Casasnovas, V. & Gail, A. Visual target and task-critical feedback uncertainty impair different stages of reach planning in motor cortex. Nat Commun 16, 3372 (2025). (https://doi.org/10.1038/s41467-025-58738-x)
ImageSource
Deutsches Primatenzentrum GmbH, Gripping in case of uncertainty, KI generiert durch Gemini, Karin Tilch