Objective: To observe the effect of oxytocin (OXT) on response inhibition in Parkinson´s disease (PD) patients using dedicated saccadic tasks.

Background: Cumulating evidence has shown the role of the neuropeptide OXT in social behavior and cognition [1]. Recent studies have also revealed that OXT has a modulatory role on inhibitory control [2,3].
The overlap pro-saccade task and anti-saccade task are two established saccadic paradigms that allow for an objective assessment of response inhibition, which is known to be impaired in PD patients.

Method: This was a randomized, placebo-controlled, double blind, crossover, monocentric pilot study. We recruited 11 male PD patients. Participants received 24 IU of a synthetic OXT nasal spray or placebo before saccadic assessment, consisting of an overlap pro-saccade and an anti-saccade task. Eye movements were recorded using an eye tracker (Tobii TX300).

Results: Participants made less anticipatory errors in the overlapping pro-saccade task (p= 0.003) after intake of OXT compared to placebo. Reaction time in correctly performed anti-saccade task were shorter after OXT intake, although this did not reach significance (p= 0.07). There were no differences in error rate in the anti-saccade task after OXT or placebo intake (p>0.05).

Conclusion: Our results show a significant reduction of the anticipatory error rate in the overlapping pro-saccade task after intake of intranasal OXT. This is in line with previously shown correlation of OXT with behavioral performance, specifically impulsivity control [2,3].
The improvement in motor impulsivity described in this eye tracking study may be reflected by a clinical improvement of overall impulsivity, particularly in PD patients with addictive behaviors. Ours is a small pilot study, and these results warrant further validation in bigger cohorts.

References: [1] T.M. Love, Oxytocin, motivation and the role of dopamine, Pharmacol. Biochem. Behav. 119 (2014) 49–60. https://doi.org/10.1016/j.pbb.2013.06.011. [2] S. Hayashi, A. Tsuru, F. Kishida, Y.K. Kim, S. Higuchi, Y. Motomura, ERP study on the associations of peripheral oxytocin and prolactin with inhibitory processes involving emotional distraction, J. Physiol. Anthropol. 38 (2019) 1–12. https://doi.org/10.1186/s40101-019-0196-z. [3] E. Demirci, S. Özmen, D.B. Öztop, Relationship between impulsivity and serum oxytocin in male children and adolescents with attention-deficit and hyperactivity disorder: A preliminary study, Noropsikiyatri Ars. 53 (2016) 291–295. https://doi.org/10.5152/npa.2015.10284.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effect-of-oxytocin-on-response-inhibition-in-parkinsons-disease-a-pilot-study/