Abnormally reduced frontal cortex activity during Trail-Making-Test in prodromal parkinson's disease–a fNIRS study

Parkinson's Disease (PD) is a neurodegenerative disorder leading to typical motor as well as a range of non-motor symptoms, including cognitive decline mainly characterized by executive deficits. The latter are known to appear years before the typical motor signs, thus representing the prodromal phase of PD. However, appropriate methods for measuring executive dysfunction in this context are not well established yet. Traditionally, executive performance is associated with frontal structures. Here, we investigated prodromal, early PD patients and healthy controls regarding their executive functioning on the behavioral and neural level, measured by the Trail-Making-Test (TMT) combined with functional near-infrared spectroscopy. We observed significantly reduced neural activity in the right dorsolateral prefrontal cortex within PD patients compared to controls completing the TMT-A and -B in contrast to the TMT-C, but no differences on a behavioral level. These promising results need to be confirmed and checked for reliability in future studies to extend the spectrum of markers applied in prodromal PD.