Measuring attention in a Parkinson's disease rat model using the 5-arm maze test

Twenty to thirty percent of patients with Parkinson's disease (PD) suffer from not only motor disorder, but also symptoms of dementia, named Parkinson's disease dementia (PDD). Cognitive deficits in PDD include memory, recognition, and attention. Although patients with PDD show fluctuation of internal attention when taking an attentional test, they perform better when provided with an external cue, indicating that they have normal external attention. We examined visuospatial attention in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD animal model using the 5-arm maze test. After an 8-day training period, followed by a 2-day pre-lesion test in the 5-arm maze, male Wistar rats received a microinfusion of MPTP into the substantia nigra pars compacta, while controls underwent a sham operation procedure. Nine days after MPTP lesioning, the rats underwent an open field test, followed by a 2-day post-lesion test in the maze. The results showed that: (1) no motor impairment was observed 9 days after MPTP lesioning; and (2) in the post-lesion 5-arm maze test, cue illumination lasting 0.5s resulted in a decrease in the percentage of correct responses compared to a 2 second cue in both the sham-operated and MPTP-lesioned groups and no difference was observed between these two groups. As far as we are aware, this is the first study examining visuospatial attention in the PD rat model using the 5-arm maze test. These results suggest that, as in patients with PDD, MPTP-induced PD rats show normal external attention function.