Abstract
The unambiguous perception of depth from motion parallax (MP) occurs with very brief temporal processing intervals. Observers require MP stimulus presentation durations on the order of 30 msec, which is increased to 75 msec with a high-contrast pattern mask. Since MP relies on an extra-retinal signal from the pursuit eye movement system, this later interval (with the mask) likely represents the time required to generate an internal signal regarding the impending pursuit signal. Alcohol intoxication is known to affect the pursuit eye movement system, the basis for a roadside sobriety test. Alcohol intoxication also increases MP thresholds, presumably due to pursuit dysfunction disrupting the integration of internal pursuit and retinal motion signals. Here we explored an alternative explanation: ethanol intoxication increases the temporal processing interval necessary for the unambiguous perception of depth from MP. To investigate this hypothesis, 16 participants completed a series of motion parallax and motion perception tasks while sober and moderately intoxicated (mean peak BAC = 0.084). These computer-generated tasks were used to assess the minimum temporal interval required to determine depth sign, stimulus window movement, and stimulus dot movements, with and without a subsequent stimulus mask. To avoid threshold issues, MP stimuli depicted stimulus geometry of about 28 cm. A step-ramp stimulus was used to assess pursuit gains and latencies at the stimulus velocities used in the psychophysical tasks. The temporal integration interval required for each of these tasks was not affected by alcohol intoxication. Curiously, while participants required the same stimulus presentation durations in both sober and intoxicated conditions, pursuit onset latency was affected by alcohol intoxication. We conclude that the ethanol intoxication does not affect the time it takes the visual system to create and integrate the component signals required for the unambiguous perception of depth from MP.
Meeting abstract presented at VSS 2015