Biology subjects

Diaz, G. J.

Publications and source records attributed to Diaz, G. J..

6 recordsLinked to original sources

bioRxiv2025

Steering in the presence of a gaze-contingent occlusion over a quarter of the visual field

Why do some cortically blind (CB) drivers who are missing vision from a quadrant or hemifield have trouble maintaining a central lane position, while others do not? A recent driving study in virtual reality showed that most patients with right-sided visual field deficits (right CB) perform similarly to controls, while most of those with left CB demonstrated a unique pattern of steering biases (Giguere et al., 2025). In this study, we tested the hypothesis that these biases could result from loss of visual information falling on the blind field. The steering and gaze behavior of 24 subjects with normal vision (mean age: 19.8 years, SD: 1.44) were recorded in a virtual reality steering task while gaze-contingent occluding masks were imposed on a quadrant of their visual field. The central five degrees of vision were spared to mimic the sparing present in most CB patients. Turn direction (left/right), turn radius (two non-constant radii), and occlusion quadrant (one of four quadrants or no occlusion) were randomized between trials. We found that the pattern of steering biases observed in CB drivers were not replicated when visually-healthy drivers were subjected to gaze-contingent masks, and we conclude that it may be a mistake to characterize the effects of cortical blindness on steering behavior as consistent with a simple omission of visual information. This insight has the potential to guide future research on CB adaptation to their visual impairments and possible interventions to improve their steering performance.

animal behavior and cognition↗

bioRxiv2025

The effect of unilateral cortical blindness on lane position and gaze behavior in a virtual reality steering task

Adults with cortically-induced blindness (CB) affecting a quarter to a half of their visual field show greater variability in lane positioning when driving compared to those with intact vision. Because humans rely on visual information from optic flow to control steering, we hypothesized that these lane biases are caused in part by a disruption to motion processing caused by CB. To investigate, we examined the steering behavior of 21 CB drivers (11 left-sided, 10 right-sided visual deficits) and 9 visually intact controls in a naturalistic virtual environment. Participants were instructed to maintain a central lane position while traveling at 19 m/s along a procedurally generated single-lane road. Turn direction (left/right) and turn radius (35m/55m/75m) varied between trials, and the quality of optic flow information was indirectly manipulated by altering the environmental texture density (low/medium/high). Right-sided CB participants maintained a similar average distance from the inner road edge as controls. Those with left-sided CB were less affected by changes in optic flow and turn direction. These differences were not explained by age, time since stroke, sparing of central vision, gaze direction, or saccade rate. Our results suggest that some left-sided CB participants place a lower weighting on optic flow information in the control of steering, possibly as a result of lateralization in the processing of motion. More broadly, our findings show that CB steering and gaze behavior are remarkably preserved despite the presence of visual deficits across large portions of the visual field.

animal behavior and cognition↗

bioRxiv2024

Optic flow density modulates corner-cutting independently of age in a virtual reality steering task

There is a critical need to understand how aging visual systems contribute to age-related increases in vehicle accidents. We investigated the potential contribution of age-related detriments in steering based on optic flow, a source of information known to play a role in navigation control. Seventeen younger adults (mean age: 21.1 years) and thirteen older adults (mean age: 57.3 years) performed a virtual reality steering task. The virtual environment depicted movement at 19 m/s along a winding road. Participants were tasked with maintaining a central lane position while experiencing 8 repetitions of each combination of optic flow density (low, medium, high), turn radius (35, 55, 75 meters), and turn direction (left, right), presented in random order. All participants cut corners, but did so less on turns with rotational flow from distant landmarks and without proximal optic flow. The magnitude of this flow-related effect was independent of age, although older adults cut corners more on all turns. An exploratory gaze analysis revealed no age-related differences in gaze behavior. The lack of age-related differences in steering or gaze behavior as a function of optic flow implies that processing of naturalistic optic flow stimuli when steering may be preserved with age.

neuroscience↗

bioRxiv2023

Coordination of gaze and action during high-speed steering and obstacle avoidance

When humans navigate through complex environments, they coordinate gaze and steering to efficiently sample the visual information needed to guide movement. Gaze and steering behavior during high-speed self-motion has been extensively studied in the context of automobile driving along a winding road. Theoretical accounts that have emerged from this work capture behavior during movement along explicit, well-defined paths over flat, obstacle-free ground surfaces. However, humans are also capable of visually guiding self-motion over uneven terrain that is cluttered with obstacles and may lack an explicit path. An extreme example of such behavior occurs during first-person view drone racing, in which pilots maneuver at high speeds through a dense forest. In this study, we explored the gaze and steering behavior of skilled drone pilots. Subjects guided a simulated quadcopter along a racecourse embedded within a forest-like virtual environment built in Unity. The environment was viewed through a head-mounted display while gaze behavior was recorded using an eye tracker. In two experiments, subjects performed the task in multiple conditions that varied in terms of the presence of obstacles (trees), waypoints (hoops to fly through), and a path to follow. We found that subjects often looked in the general direction of things that they wanted to steer toward, but gaze fell on nearby objects and surfaces more often than on the actual path or hoops. Nevertheless, subjects were able to perform the task successfully, steering at high speeds while remaining on the path, passing through hoops, and avoiding collisions. Furthermore, in conditions that contained hoops, subjects adapted how they approached the most immediate hoop in anticipation of the position (but not the orientation) of the subsequent hoop. Taken together, these findings challenge existing models of steering that assume that steering is tightly coupled to where actors look.

neuroscience↗

bioRxiv2023

Transfer of figure-ground segregation learning is facilitated by a cross-modal auditory feature-based attention cue.

This study tested the role of a cross-modal feature based attention (FBA) cue on perceptual learning and spatial transfer. The trained task was figure-ground segregation in the motion domain. The experiment involved a pre-test, ten days of training, and a post-test. Twelve visually intact participants were immersed in a virtual environment and tasked with identifying the location and motion direction of a peripheral 10{whitebullet}aperture of semi-coherently moving dots embedded at randomized locations within whole-field random dot motion. The aperture contained both randomly moving dots and signal dots which had global leftward or rightward motion. To manipulate motion coherence, a 3-up-1-down staircase adjusted the direction range of the signal dots in response to segregation judgments. The dot stimulus was preceded by a 1s white-noise spatialized auditory cue emitted from the fixation point (neutral group), or from an emitter moving in the direction of signal dots at 80{whitebullet}/s in a horizontal arc centered on the fixation point (FBA cue group). Visual feedback indicated the selected and true aperture locations, and correctness of the motion direction judgment. Analysis measured MD discrimination within the aperture as well as segregation ability, both measured in terms of direction range threshold (DRT). At trained locations, MD DRT improved similarly in FBA and neutral groups, and learning was retained when the pre-cue was removed ({Delta}DRT from pretest to posttest: 61{+/-}10{whitebullet}(SD) FBA, 74{+/-}10{whitebullet}neutral), and transferred to untrained locations (41{+/-}10{whitebullet}FBA, 45{+/-}10{whitebullet}neutral). DRT for localization also improved in both groups when pre-cues were removed (49{+/-}10{whitebullet}FBA, 44{+/-}10{whitebullet}neutral), but only the FBA group showed full transfer of learning to untrained locations in the segregation task (32{+/-}10{whitebullet}FBA, 23{+/-}10{whitebullet}neutral). In summary, transfer occurred for both motion direction and segregation tasks, but the segregation transfer required the presence of the cross-modal FBA cue during training.

neuroscience↗

bioRxiv2023

Multisensory perceptual learning in virtual reality may facilitate transfer to untrained locations but is impacted by training procedures.

Visual training improves performance in visually-intact and visually-impaired participants, making it useful as a rehabilitation tool. An interesting question in rehabilitation is whether invocation of multisensory integration could increase training efficacy. To investigate, participants completed a 10-day training experiment wherein they repeatedly performed a 4-way global motion direction discrimination task. On each trial, participants were presented with a 5{degrees} diameter visual global motion stimulus placed in a gaze-contingent manner at 10{degrees} azimuth/elevation. The visual-only group was presented the unimodal visual stimulus. However, for the auditory/visual (AV) group, the visual stimulus was paired with a pulsed white-noise auditory cue moving along in a direction consistent with the horizontal component of the visual motion stimulus. Direction range thresholds (DRT) were computed daily. The motion direction discrimination learning transferred fully in both groups, regardless of the presence of a feature-based attention cue. However, the figure-ground segregation learning only fully transferred to untrained locations with the addition of the feature-based attention cue. These results speak to the multiple levels of processing on which perceptual learning can operate. PACS0000, 1111 2000 MSC0000, 1111

neuroscience↗