Cognitive trajectories in Parkinson's disease patients, a review on the impact of subthalamic deep brain stimulation (STN-DBS) and emerging adaptive strategies.

While deep brain stimulation (DBS) is well-established for managing motor symptoms in Parkinson's disease (PD) and improving patient's quality of life, its impact on cognition is still not properly addressed. Cognitive impairment in PD often affects verbal fluency, attention, and executive functions, and may interact with disease progression, dopaminergic medication, and stimulation parameters. These outcomes are shaped not only by the stimulation itself but also by factors such as baseline cognitive status, lead location, disease heterogeneity, and parameter selection. The emerging development of closed-loop DBS (CL-DBS) offers a promising tailored neuromodulation strategy that may help reduce DBS side effects while enhancing non-motor function. Given the extensive yet heterogeneous literature on cognitive outcomes after STN-DBS, this review integrates mechanistic insights from human and animal studies to clarify how stimulation parameters, anatomical targeting, and network-level dynamics influence postoperative cognitive trajectories. We summarize established cognitive effects of conventional DBS, emphasize sources of interindividual variability, and evaluate how adaptive stimulation paradigms may modulate cognitive and decision-making processes. Finally, we outline translational considerations for biomarker development and personalized neuromodulation strategies aimed at preserving cognition while maintaining motor benefit.