title: Medications influencing central cholinergic pathways affect fixation stability, saccadic response time and associated eye movement dynamics during a temporally-cued visual reaction time task.
abstract: Anticholinergic medications largely exert their effects due to actions on the muscarinic receptor, which mediates the functions of acetylcholine in the peripheral and central nervous systems. In the central nervous system, acetylcholine plays an important role in the modulation of movement.
  
  
  
  This study investigated the effects of over-the-counter medications with varying degrees of central anticholinergic properties on fixation stability, saccadic response time and the dynamics associated with this eye movement during a temporally-cued visual reaction time task, in order to establish the significance of central cholinergic pathways in influencing eye movements during reaction time tasks.
  
  
  
  Twenty-two participants were recruited into the placebo-controlled, human double-blind, four-way crossover investigation. Eye tracking technology recorded eye movements while participants reacted to visual stimuli following temporally informative and uninformative cues. The task was performed pre-ingestion as well as 0.5 and 2 h post-ingestion of promethazine hydrochloride (strong centrally acting anticholinergic), hyoscine hydrobromide (moderate centrally acting anticholinergic), hyoscine butylbromide (anticholinergic devoid of central properties) and a placebo.
  
  
  
  Promethazine decreased fixation stability during the reaction time task. In addition, promethazine was the only drug to increase saccadic response time during temporally informative and uninformative cued trials, whereby effects on response time were more pronounced following temporally informative cues. Promethazine also decreased saccadic amplitude and increased saccadic duration during the temporally-cued reaction time task.
  
  
  
  Collectively, the results of the study highlight the significant role that central cholinergic pathways play in the control of eye movements during tasks that involve stimulus identification and motor responses following temporal cues.
authors.affiliation: Menzies Health Institute Queensland, Griffith University, Gold Coast, QLD, Australia.|School of Pharmacy, Griffith University, Gold Coast, QLD, Australia.
authors.forename: Preshanta
authors.initials: P
authors.lastname: Naicker
authors.affiliation: Menzies Health Institute Queensland, Griffith University, Gold Coast, QLD, Australia.|School of Pharmacy, Griffith University, Gold Coast, QLD, Australia.
authors.forename: Shailendra
authors.initials: S
authors.lastname: Anoopkumar-Dukie
authors.affiliation: Menzies Health Institute Queensland, Griffith University, Gold Coast, QLD, Australia.|School of Pharmacy, Griffith University, Gold Coast, QLD, Australia.
authors.forename: Gary D
authors.initials: GD
authors.lastname: Grant
authors.affiliation: Institute for in silico Medicine, University of Sheffield, Sheffield, UK.|Department of Mechanical Engineering, University of Sheffield, Sheffield, UK.
authors.forename: Luca
authors.initials: L
authors.lastname: Modenese
authors.affiliation: Menzies Health Institute Queensland, Griffith University, Gold Coast, QLD, Australia. j.kavanagh@griffith.edu.au.|School of Allied Health Sciences, Griffith University, Gold Coast, QLD, Australia. j.kavanagh@griffith.edu.au.
authors.forename: Justin J
authors.initials: JJ
authors.lastname: Kavanagh
mesh_terms: D000293:Adolescent; D000328:Adult; D002086:Butylscopolammonium Bromide / Q000494:pharmacology*; D018680:Cholinergic Antagonists / Q000494:pharmacology*; D018592:Cross-Over Studies; D003463:Cues; D004311:Double-Blind Method; D005133:Eye Movements / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D011398:Promethazine / Q000494:pharmacology*; D011930:Reaction Time / Q000187:drug effects*; D012438:Saccades / Q000187:drug effects; D012601:Scopolamine / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D018680:Cholinergic Antagonists; D002086:Butylscopolammonium Bromide; D012601:Scopolamine; D011398:Promethazine
keywords: Anticholinergic; Eye movement dynamics; Fixation stability; Saccadic response time; Temporally informative cue; Temporally uninformative cue