Visual Stimuli Presentation and Eye Tracking Protocol

Visual stimuli were presented using a LED projector, back-projected on a rear-projection screen that was positioned at a distance of 52 cm from the animal’s eyes (PROPixx, VPixx Technologies, Saint-Bruno, Canada). The MonkeyLogic software package developed in MATLAB (https://www.brown.edu/Research/monkeylogic/; https://monkeylogic.nimh.nih.gov/; Hwang et al., 2019 (link)) was used for stimulus presentation, behavioral control and recording of eye position. A photodiode was used to measure stimulus timing. Eye position was continuously monitored with an infrared eye tracking system (ISCAN model ETL-200, Woburn, MA) and eye traces were saved using MonkeyLogic. Trials were aborted if eye position deviated from the fixation point (threshold typically 1 dva radius).