title: Stimulus-specific pupil dynamics measured in birds (Gallus gallus domesticus) in vivo with ultrahigh resolution optical coherence tomography.
abstract: OBJECTIVE
  To demonstrate the ability of high speed, ultrahigh-resolution optical coherence tomography (UHR-OCT) to measure and characterize in vivo visual stimulus-specific pupil dynamics in birds.
  
  
  METHODS
  Ten two-week old White Leghorn (Gallus gallus domesticus) chickens were imaged in this study. The chickens were dark-adapted for 1 hour and anesthetized with 2% isoflurane prior to the imaging procedure. Blue, green, and red single flash visual stimuli of 7 ms duration were used to evoke pupillary responses. UHR-OCT cross-sectional images of the pupil were acquired prior, during, and for several seconds after the visual stimuli onset. Images were processed with a novel custom automatic algorithm, designed to determine the pupil diameter changes over time.
  
  
  RESULTS
  Results from this study show that the pupillary constriction begins with the onset of the visual stimuli; however, maximum pupil constriction occurs ∼150 ms later. No statistically significant variation in the timing of the maximum pupillary constriction was observed for stimuli of different colors. However, significant variation was observed in the maximum pupil constriction amplitudes, between red-green and red-blue stimuli, but not between blue-green stimuli. Furthermore, the magnitude of the maximum pupil constriction decreased monotonically with time under isoflurane anesthesia.
  
  
  CONCLUSIONS
  We demonstrated, for the first time, measurements of visually evoked pupillary dynamics in animals using high speed UHR-OCT. The results suggest dependence of the pupillary dynamics on the color of the visual stimulus, and adverse effects of isoflurane anesthesia on the visually evoked pupillary responses in chickens.
authors.affiliation: Department of Physics and Astronomy, University of Waterloo, Ontario, Canada.
authors.forename: Alireza Akhlagh
authors.initials: AA
authors.lastname: Moayed
authors.forename: Vivian
authors.initials: V
authors.lastname: Choh
authors.forename: Sepideh
authors.initials: S
authors.lastname: Hariri
authors.forename: Chenyi
authors.initials: C
authors.lastname: Liu
authors.forename: Alexander
authors.initials: A
authors.lastname: Wong
authors.forename: Kostadinka
authors.initials: K
authors.lastname: Bizheva
mesh_terms: D000818:Animals; D002645:Chickens / Q000502:physiology*; D007089:Image Enhancement / Q000379:methods*; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology*; D011930:Reaction Time; D041623:Tomography, Optical Coherence / Q000379:methods*