Action language deficit ¿Preclinic sign of Parkinson's? Literature review

Abstract

Parkinson's disease (PD) is a late-diagnosed neurodegenerative condition, sometimes present almost a decade before its confirmation. It is characterized by involuntary movements such as tremor, slowness, rigidity and loss of postural control related to dopamine depletion in the substantia nigra. In addition to motor symptoms, there are complications with the autonomic system, and neuropsychological symptoms such as depression or cognitive alterations, including deficiency in verbal fluency. Aligned with the embodiment theory and the concept of motor cognition -where cognition is linked to action- some researchers have specifically observed a deficit in action language (ALD) in movement disorders such as PD and suggest that this could be a preclinical sign of PD. This review aimed to present an overview of a set of publications on DLA in Spanish and English between 2013 and 2023, and to analyze whether there is a dominant position on the topic. Through the PRISMA model, 3 databases were explored: Scopus, PubMed and Web of Science. After applying the inclusion criteria, 32 publications were obtained. Most of them supported the DLA, but other experiments -also included- could not replicate the success. The main challenges seem to be the standardization and adaptation of tests to different languages. It was concluded that there is a majority of publications supporting this deficit in PD but it is not yet recommended to consider it as a preclinical sign in the diagnosis.