Neuropsychiatric Burden Is a Predictor of Early Freezing and Motor Progression in Drug-Naïve Parkinson’s Disease

Background: Neuropsychiatric symptoms (NPS) are the most common non-motor symptom in Parkinson’s disease (PD). Objective: To investigate the association between the burden of NPS and motor prognosis in patients with PD. Methods: We enrolled 329 drug-naïve patients with PD, who was non-demented and followed-up≥2 years after their first visit to the clinic with baseline dopamine transporter (DAT) imaging and neuropsychiatric inventory (NPI) scores. We performed a survival analysis and a linear mixed model analysis to assess longitudinal motor outcomes according to the NPI total score. Results: The Kaplan-Meier analysis showed no difference in the development of levodopa-induced dyskinesia and wearing-off according to the NPI total score. However, higher burden of NPI total score was associated with earlier freezing of gait (FOG) development in the time-dependent Cox regression models after adjusting for age at symptom onset, sex, disease duration, Unified PD Rating Scale motor score, baseline Mini-Mental State Examination score, DAT activity in the posterior putamen and levodopa-equivalent daily dose (LEDD) (Hazard ratio 1.047, p = 0.002). A linear mixed model analysis revealed that patients with a higher NPI total score had a more rapid LEDD increment (NPI×time, p = 0.003). Among 52 patients with PD who eventually developed FOG during the follow-up period, there was a significant correlation between the NPI total score and time with FOG development (γ= –0.472; p = 0.001) after adjusting for confounding factors. Conclusion: The present study demonstrated that the severity of NPS is a predictor of early freezing and motor progression in patients with PD.

Size-related boldness is not altered by stomach flushing in a terrestrial salamander

Animal personality is a relatively neglected field in amphibian research. In this study we assessed the influence of stomach flushing, a non-lethal technique used in amphibian dietary studies, on the boldness behaviour of the cave salamander Speleomantes strinatii. The time of emergence from a shelter located in an unfamiliar environment (a proxy for individual boldness) was measured in 26 cave salamanders before and after stomach flushing, while 14 non-flushed salamanders were tested as controls. Boldness was a repeatable behaviour for salamanders and larger individuals emerged from their shelter more rapidly than smaller ones. Linear mixed model analysis showed that flushing, sex and body condition had no effect on this behaviour. These findings are promising in the framework of the study of salamander personality. In particular, our results will be useful when exploring the relationship between individual trophic strategy and boldness, aggression or exploration behaviours in terrestrial salamanders.