Parkinson's disease (PD) is a neurodegenerative disease affecting many physiological systems essential for balance control. New findings suggest that intensive, challenging and cognitively demanding exercises could induce neuroplasticity in PD. A new balance training (the HiBalance program) have therefore been developed; emphasizing critical aspects of balance control through highly challenging and progressive exercises incorporating dual/multi-tasking (Conradsson et al, 2012). In an RCT, the HiBalance-program was shown to improve balance, gait and physical activity level in favor for the training group (Conradsson et al, 2015). In this proposal the investigators will combine physiotherapy, neurology and neuroimaging to characterise and determine the effects on physical and cognitive symptoms as well as structural and functional changes and wet biomarkers in the brain after the training.