title: Disruption of pupil size modulation correlates with voluntary motor preparation deficits in Parkinson's disease.
abstract: Pupil size is an easy-to-measure, non-invasive method to index various cognitive processes. Although a growing number of studies have incorporated measures of pupil size into clinical investigation, there have only been limited studies in Parkinson's disease (PD). Convergent evidence has suggested PD patients exhibit cognitive impairment at or soon after diagnosis. Here, we used an interleaved pro- and anti-saccade paradigm while monitoring pupil size with saccadic eye movements to examine the relationship between executive function deficits and pupil size in PD patients. Subjects initially fixated a central cue, the color of which instructed them to either look at a peripheral stimulus automatically (pro-saccade) or suppress the automatic response and voluntarily look in the opposite direction of the stimulus (anti-saccade). We hypothesized that deficits of voluntary control should be revealed not only on saccadic but also on pupil responses because of the recently suggested link between the saccade and pupil control circuits. In elderly controls, pupil size was modulated by task preparation, showing larger dilation prior to stimulus appearance in preparation for correct anti-saccades, compared to correct pro-saccades, or erroneous pro-saccades made in the anti-saccade condition. Moreover, the size of pupil dilation correlated negatively with anti-saccade reaction times. However, this profile of pupil size modulation was significantly blunted in PD patients, reflecting dysfunctional circuits for anti-saccade preparation. Our results demonstrate disruptions of modulated pupil responses by voluntary movement preparation in PD patients, highlighting the potential of using low-cost pupil size measurement to examine executive function deficits in early PD.
authors.affiliation: Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada K7L 3N6. Electronic address: josh.wang@queensu.ca.
authors.forename: Chin-An
authors.initials: CA
authors.lastname: Wang
authors.affiliation: Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Hailey
authors.initials: H
authors.lastname: McInnis
authors.affiliation: Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Donald C
authors.initials: DC
authors.lastname: Brien
authors.affiliation: Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada K7L 3N6; Department of Medicine, Queen's University, Kingston, Ontario, Canada.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Pari
authors.affiliation: Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada K7L 3N6; Department of Medicine, Queen's University, Kingston, Ontario, Canada; Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada. Electronic address: doug.munoz@queensu.ca.
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Munoz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015835:Ocular Motility Disorders / Q000209:etiology*; D010300:Parkinson Disease / Q000150:complications*; D010775:Photic Stimulation; D011596:Psychomotor Disorders / Q000209:etiology*; D011680:Pupil; D011930:Reaction Time / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D013223:Statistics as Topic
keywords: Executive function; Frontal eye field; Motor preparation; Oculomotor; Preparatory set; Pupillary response; Reaction times; Superior colliculus