Toward a Multi-Modal Brain-Body Assessment in Parkinson's Disease: A Systematic Review in fNIRS

Parkinson's disease (PD) causes impairments in cor-1 tical structures leading to motor and cognitive symptoms.While 2 common disease management and treatment strategies mainly 3 depend on the subjective assessment of clinical scales and pa-4 tients' diaries, research in recent years has focused on advances 5 in automatic and objective tools to help with diagnosing PD and 6 determining its severity.Due to the link between brain structure 7 deficits and physical symptoms in PD, objective brain activity and 8 body motion assessment of patients have been studied in the liter-9 ature.This study aimed to explore the relationship between brain 10 activity and body motion measures of people with PD to look at the 11 feasibility of diagnosis or assessment of PD using these measures.12 In this study, we summarised the findings of 24 selected papers 13 from the complete literature review using the Scopus database.Se-14 lected studies used both brain activity recording using functional 15 near-infrared spectroscopy (fNIRS) and motion assessment using 16 sensors for people with PD in their experiments.Results include: 17 1) The most common study protocol is a combination of single 18 tasks.2) Prefrontal cortex is mostly studied region of interest in the 19 literature.3) Oxygenated haemoglobin (HbO 2 ) concentration is the 20 predominant metric utilised in fNIRS, compared to deoxygenated 21 haemoglobin (HHb).4) Motion assessment in people with PD is 22 mostly done with inertial measurement units (IMUs) and electronic 23 walkway.5) The relationship between brain activity and body mo-24 tion measures is an important factor that has been neglected in the 25 literature.