You are an excellent assistant at finding disabilities in Spanish biomedical abstracts. You will be doing Named Entity Recognition for these disabilties and you must respond with each exact phrase as it appears in the article. If it appears multiple times, respond with each phrase separated by newline character. If there are no disabilities, respond with NA.

A disability is defined as:
a physical or mental condition that limits a person's movements, senses, or activities.


Abstract:

Introduction . Parkinson's disease is a progressive neurodegenerative disorder characterised by a loss of dopaminergic neurons in the substantia nigra pars compacta , which results in a significant decrease in dopamine levels and consequent functional motor impairment . Development . Although its aetiology is not fully understood , several pathogenic mechanisms , including oxidative stress , have been proposed . Current therapeutic approaches are based on dopamine replacement drugs ; these agents , however , are not able to stop or even slow disease progression . Novel therapeutic approaches aimed at acting on the pathways leading to neuronal dysfunction and death are under investigation . Conclusions . In recent years , such natural molecules as polyphenols , alkaloids , and saponins have been shown to have a neuroprotective effect due to their antioxidant and anti - inflammatory properties . The aim of our review is to analyse the most relevant studies worldwide addressing the benefits of some phytochemicals used in in vitro models of Parkinson's disease . 
functional motor impairment