Humans gradually integrate sudden gain or loss of visual information into spatial orientation perception

Abstract

Introduction: Vestibular and visual information is used in determining spatial orientation. Existing computational models of orientation perception focus on the integration of visual and vestibular orientation information when both are available. It is well-known, and computational models capture, differences in spatial orientation perception with visual information or without (i.e., in the dark). For example, during earth vertical yaw rotation at constant angular velocity without visual information, humans perceive their rate of rotation to decay. However, during the same sustained rotation with visual information, humans can continue to more accurately perceive self-rotation. Prior to this study, there was no existing literature on human motion perception where visual information suddenly become available or unavailable during self-motion.

Methods: Via a well verified psychophysical task, we obtained perceptual reports of self-rotation during various profiles of Earth-vertical yaw rotation. The task involved transitions in the availability of visual information (and control conditions with visual information available throughout the motion or unavailable throughout).

Results: We found that when visual orientation information suddenly became available, subjects gradually integrated the new visual information over ~10 seconds. In the opposite scenario (visual information suddenly removed), past visual information continued to impact subject perception of self-rotation for ~30 seconds. We present a novel computational model of orientation perception that is consistent with the experimental results presented in this study.

Discussion: The gradual integration of sudden loss or gain of visual information is achieved via low pass filtering in the visual angular velocity sensory conflict pathway. In conclusion, humans gradually integrate sudden gain or loss of visual information into their existing perception of self-motion.

Keywords: disorientation; orientation perception; pilot; spatial orientation; vestibular; vestibular orientation; visual orientation.

Figure 1

Plot matrix to show underlying motion profiles and visual information availability used during testing. Panel (A) shows the unidirectional motion profile in which for the test condition, visual information suddenly appeared after 88 seconds. Panel (B) shows a bidirectional motion profile in which for the test condition visual information suddenly disappeared after 49 seconds. Panel (C) shows the same motion profile as in panel (B), but where the visual information suddenly appeared after 103 seconds. Panel (D) is the same motion profile as panels (C) and (D), but where the visual information suddenly appeared after 47 seconds. Panels (E) and (F) show the same bidirectional motion profile, but in panel (E) the visual information suddenly disappears after 64 seconds, while in panel (F) the visual information suddenly appears after 45 seconds. Five of six motion profiles are bidirectional and have near constant change in angular velocity to reduce motion predictability. The shaded area indicates when subjects were and were not provided with visual angular velocity information.

Figure 2

Left: Photograph to show experimental apparatus. Testing was conducted in the dark and with the rear door closed (lights on for photograph). Right: Visual display provided to subjects when visual information were made available. The dot pattern moved in the opposite direction of rotation to provide congruent angular visual velocity information.

Figure 3

Plot to show experimental data for one motion profile-test condition combination (Figure 1E). Visual information/without visual information control conditions for that motion profile are shown in navy/yellow. Green is average orientation perception for the test condition. Notably, the green line begins by closely tracking the yellow (with visual information control condition) line. After the visual information is suddenly removed (gray part of plot), the green line transitions to tracking the navy (no visual information control condition) line.

Figure 4

Remaining experimental data. Shaded areas of each plot indicate where visual information was not provided during the test condition. Each plot contains data from the control conditions. Navy is the control condition with no visual information, yellow is the control condition with visual information. Green is the test condition. Panel (A) shows the results from the motion profile in Figure 1C. Panel (B) shows the results from the motion profile in Figure 1C. Panel (C) shows the results from the motion profile in Figure 1D. Panel (D) shows the results from the motion profile in Figure 1B. Panel (E) shows the results from the motion profile in Figure 1A.

Figure 5

Model to show semicircular canal and visual angular velocity pathways. Additional parts of the model exist (e.g., otolith sensing, visual position and vertical) but only the SCCs and visual angular velocity pathway were being stimulated in this experiment. The addition of the low pass filter (in yellow) in the visual angular velocity sensory conflict pathway captures the gradual integration of sudden loss or gain of visual information.

Figure 6

Two trials which were not used in fitting model parameters. In black is the predicted perception of the updated model. We note that addition of an appropriately tuned low pass filter removes the discontinuity seen in the original mode (dashed green). Panel (A) shows the model-predicted perception for the motion profile in Figure 1B, with the corresponding empirical perception from the test condition shown in Figure 4D. Panel (B) shows the model-predicted perception from the motion profile in Figure 1A, with the corresponding empirical perception from the test condition shown in Figure 4E.

Figure 7

Plot matrix to show original model prediction against updated model prediction for remaining trials. The data (shown in solid green) was used to fit the parameters of the updated model. Panel (A) shows the model-predicted perception for the motion profile in Figure 1F, with the corresponding empirical perception from the test condition shown in Figure 4B. Panel (B) shows the model-predicted perception for the motion profile in Figure 1E, with the corresponding empirical perception from the test condition shown in Figure 3. Panel (C) shows the model-predicted perception for the motion profile in Figure 1C, with the corresponding empirical perception from the test condition shown in Figure 4A. Panel (D) shows the model-predicted perception for the motion profile in Figure 1D, with the corresponding empirical perception from the test condition shown in Figure 4C.

Figure 8

Plot to show difference in observer model prediction with the addition of the low pass filter in the visual angular velocity pathway. Here, we note that the addition of low pass filtering does not substantially change the observer prediction when the visual information availability condition does not change. Therefore, the updated model is still valid for cases where the previous model was valid (e.g., perception predictions with visual angular velocity information available).