Stimuli were generated on Apple iMac using MATLAB (MathWorks) and MGL (Gardner et al., 2018 (link)), and were presented on a 61-inch screen (BenQ XL242OZ) positioned 57 cm in front of the participant. A portion of the participant group (five observers) were tested with a VIEWpixx/3D display (Vpixx Technologies). The stimuli consisted of a stream of central digits, and peripheral stimuli that appeared on 75% of trials. The peripheral stimuli were gratings at one of two possible contrast levels (high: 1 or low: 0.2 Michelson contrast) and at one of five possible spatial frequencies [0.5, 0.8, 1.3, 2, 3.2 cycles per degree (cpd)]. Separately, 15 participants were tested with peripheral gratings at one of five possible contrast levels (0.2, 0.3, 0.4, 0.7, 1 Michelson contrast) and five spatial frequencies. The gratings extended from 1.3° eccentricity to the edge of the screen and had the same mean luminance as the gray background (103.60 cd/m2). During each stimulus trial, four gratings appeared at random orientations, for 500 ms each.
Viewpixx 3d display
Manufactured by VPixx Technologies
Sourced in Canada
The ViewPixx 3D display is a high-performance visual stimulation device developed by VPixx Technologies. It is designed to provide accurate and reliable 3D visual presentation for research and clinical applications. The ViewPixx 3D display offers precise control over the presentation of visual stimuli, enabling researchers to conduct precise and controlled experiments.
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5 protocols using viewpixx 3d display
1
Peripheral Stimulus Presentation in Vision Research
2
Coherent Motion Perception Experiment
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We presented stimuli on a VIEWPixx 3D display (1,920 ϫ 1,080 pixels, 520 ϫ 295 mm; VPixx Technologies) positioned at a viewing distance of 350 mm. The stimulation protocol has been previously described (Zavitz et al. 2019) (link). Briefly, we displayed a sheet of white dots on a black background that moved coherently, with no noise, in 1 of 12 equally spaced directions and at 1 of 3 speeds (5, 10, and 20 deg/s). The stimulus moved in one direction for 500 ms and was followed by a black screen for 500 ms before another, random, direction was presented. Each direction was presented 120 times. We used Psychophysics Toolbox to generate stimuli in MATLAB (Brainard 1997; (link)Kleiner et al. 2007; Pelli 1997) (link).
3
Contrast perception ERP protocol
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Event-related potentials were recorded using an ANT Neuroscan EEG system and a 64channel Waveguard cap with electrodes arranged according to the 10/20 system. The ground electrode was positioned at AFz, and a whole head average was used as a reference. Data were digitised at 1kHz using the ASALab software. Stimuli were presented on a ViewPixx 3D display (VPixx Technologies Inc., Quebec, Canada) running in M16 mode (16-bit luminance resolution) with a mean luminance of 51cd/m 2 and a refresh rate of 120Hz, using Matlab and elements of the Psychophysics Toolbox (Brainard, 1997; Kleiner, Brainard, & Pelli, 2007; Pelli, 1997) . The display was gamma corrected using a Minolta LS110 photometer, fitting the data with a 4-parameter exponential function, and transforming stimulus intensities using the inverse of the function to ensure linearity. Participants were seated in a darkened room 57cm away from the display. Instructions for the task were to 'indicate the grating that appeared higher in contrast'. They were asked to fixate on a central cross throughout the task and used a mouse to indicate their responses. There were 200 trials per target contrast (1000 trials total, yielding 2000 stimulus-locked ERPs). The task was run in 5 blocks of approximately 8 minutes, with short breaks in between.
4
Gaze-Contingent Central Scotoma Simulation
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The performance of the experiment and of the data acquisition were carried out using a gaze contingent setup based on MATLAB, the Psychtoolbox (Brainard, 1997; (link)Kleiner, Brainard, & Pelli, 2007) , the Eyelink toolbox (Cornelissen, Peters, & Palmer, 2002) , the Eyelink 1000 Plus eye tracker (SR Research, Ltd., Ontario, Canada) , and a VIEWPixx/3D display (VPixx Technologies, Saint-Bruno, Canada) with a vertical refresh rate of 100 Hz and a spatial resolution of 1,920 by 1,080 pixels.
To simulate the central scotoma, a gaze-contingent round mask was presented at the momentary eye position. Scotoma presentation was temporally delayed by less than 20 ms after eye position detection. Vertical and horizontal positions of the right eye were recorded at a spatial resolution of 0.018 and 1 kHz while the left eye was patched.
A chin rest was used to stabilize the head and to locate the eyes at a distance of 62 cm from the display.
To simulate the central scotoma, a gaze-contingent round mask was presented at the momentary eye position. Scotoma presentation was temporally delayed by less than 20 ms after eye position detection. Vertical and horizontal positions of the right eye were recorded at a spatial resolution of 0.018 and 1 kHz while the left eye was patched.
A chin rest was used to stabilize the head and to locate the eyes at a distance of 62 cm from the display.
5
Binocular 3D Visual Presentation and EEG Recording
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All stimuli were presented using a gamma corrected ViewPixx 3D display (VPixx technologies, Canada) driven by a Mac Pro. Binocular separation with minimal crosstalk was achieved by synchronizing the refresh rate of the display with the toggling of a pair of Nvidia stereo shutter goggles using an infra-red signal. Monitor refresh rate was set to 120Hz, meaning that each eye was updated at 60Hz (every 16.67 msec). Display resolution was set to 1920 X 1080 pixels. A single pixel subtended 0.027° of visual angle (1.63 arc min) when viewed from 57 cm. The mean luminance of the display viewed through the shutter goggles was 26 cd/m 2 . EEG signals were recorded from 64 electrodes distributed across the scalp according to the 10/20 EEG system (Chatrian et al., 1985) (link) in a WaveGuard cap (ANT Neuro, Netherlands). We monitored eye blinks with an electrooculogram, which consisted of bipolar electrodes placed above the eyebrow and atop of the cheek on the left side of the participant's face. Stimulus-contingent triggers were sent from the ViewPixx display to the amplifier using a parallel cable. Signals were amplified and digitized using a PC with the ASAlab software (ANT Neuro, Netherlands). All EEG data were imported into MATLAB (Mathworks, MA, USA) and analysed offline.
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