Early Changes in Saccadic Eye Movement in Hemiparkinsonian MPTP-Treated Monkeys

Abstract

The saccadic eye movements declining given the development of Parkinson's disease (PD) still deserves thorough analysis. Recent studies confirmed that PD patients show poor saccadic control in visuomotor tasks. The purpose of this study was to investigate the dynamics of saccades parameters at the development of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD. The gradual decline of saccadic control was studied in two monkeys that executed the visuomotor task with low doses of MPTP being injected at a prolonged period of time. The experiment included investigating the horizontal, vertical, oblique visually guided saccades as well as the corrective saccades triggered by stimuli onset in various loci within a two-dimensional visual field in the Gap-Step-Overlap paradigm. Our study revealed that the execution of visually guided saccades with small amplitude and corrective saccades changed dramatically with MPTP-model progressing. These changes are also confirmed statistically at the presymptomatic stage of MPTP syndrome. Not only our study gives a robust report of PD dynamics development and saccadic control but the obtained data could also be helpful in developing methods for the early diagnosis of PD.

Multiple step saccades in simply reactive saccades could serve as a complementary biomarker for the early diagnosis of Parkinson’s disease

“…Stimulating the frontal eye field and supplementary eye field with transcranial magnetic stimulation (TMS) increased the incidence of MSS ( van Donkelaar et al, 2009 ). Loss of dopaminergic neurons in the basal ganglia increased the incidence of MSS, as observed in PD patients ( Kimmig et al, 2002 ; Blekher et al, 2009 ) and PD monkeys ( Tereshchenko et al, 2015 ). Lesions in the cerebellum caused an increase in MSS incidence in human and non-human primates ( Avanzini et al, 1979 ).…”

“…While the reported incidences of MSS are consistent for memory guided saccades among previous studies, the results are inconsistent for reactive saccades. Some studies reported that, compared with elderly healthy subjects, the incidences of MSS are significantly higher in both PD patients ( Jones and DeJong, 1971 ; Corin et al, 1972 ; White et al, 1983 ) and PD monkeys ( Brooks et al, 1986 ; Tereshchenko et al, 2015 ), but others reported no significant difference ( Crawford et al, 1989 ; Lueck et al, 1990 , 1992 ; Van Gisbergen et al, 1992 ; Kimmig et al, 2002 ; Blekher et al, 2009 ). We think that a possible reason for such inconsistency might be the different definitions of MSS.…”

Multiple step saccades are generated by internal real-time saccadic error correction

“…Supportively, previous studies have found that suppressing the activity of the frontal eye field (FEF) and supplementary eye field by transcranial magnetic stimulation (TMS) increased the incidence of MSS (van Donkelaar et al, 2009). Moreover, damage of dopaminergic neurons in the basal ganglia increased the incidence of MSS, as observed in PD patients (Kimmig et al, 2002;Blekher et al, 2009) and in PD monkeys (Tereshchenko et al, 2015).…”