Anything that can help get more balance and coordination info to the higher centers is a plus for Parkinsons folks, and the texture of the surface they are walking on or the texture of the insole is no different. The more afferent info we can get in through the tactile receptors, joint mechanoreceptors and muscle receptors like the spindles and golgi tendon organs, the better. These all feed (eventually or sometimes directly) to the cerebellum, the king of balance.
In this study they placed little half spheres at the distal phalanx of the hallux, heads of metatarsophalangeal joints and heel. Theses are all areas of increased cortical representation when you look at the sensory homunculus. They wore them for a week and plantar sensation and stride length both improved, but only the increased plantar sensation remained. Neuroplasticity takes time and we are willing to bet that if they wore them longer, the results would have been more profound.
Sometimes the simplest interventions can go a long way.
Lirani-Silva E, Vitorio R, Barbieri FA, et al. Continuous use of textured insole improve plantar sensation and stride length of people with Parkinson disease: A pilot study. Gait Posture 2017;58:495-497. [