Self-motion Simulation Research Articles

Brain Processing of Visual Self-Motion Stimuli in Patients With Migraine: An fMRI Study.

To investigate the behavioral and neuronal responses of patients with migraine to a visual simulation of self-motion through a virtual roller coaster ride in comparison to controls. Twenty consecutive patients with migraine from a university-based hospital headache clinic and 20 controls were included. Participants underwent an experiment where a visually displayed self-motion paradigm was presented based on customized roller coaster videos during fMRI. Within each video, blocks of motion stimulation were interleaved with low-speed upward motion in a random order. In the scanning intervals and after the experiment, participants rated their perceived level of vestibular symptoms and motion sickness during the videos. We hypothesized that patients with migraine will perceive more motion sickness and that it correlates with different central processing and brain responses. Compared to controls, patients with migraine reported more dizziness (65% vs 30%; p = 0.03) and motion sickness (Simulator Sickness Questionnaire score 47.3 [95% confidence interval (CI), 37.1, 57.5] vs 24.3 [95% CI, 18.2, 30.4]) as well as longer symptom duration (01:19 minutes [95% CI, 00:51, 01:48] vs 00:27 minutes [95% CI, 00:03, 00:51]) and intensity (visual analogue scale score 0-100, 22.0 [95% CI, 14.8, 29.2] vs 9.9 [95% CI, 4.9, 14.7]) during the virtual roller coaster ride. Neuronal activity in patients with migraine was more pronounced in clusters within the superior (contrast estimate 3.005 [90% CI, 1.817, 4.194]) and inferior occipital gyrus (contrast estimate 1.759 [90% CI, 1.062, 2.456]), pontine nuclei (contrast estimate 0.665 [90% CI, 0.383, 0.946]), and within the cerebellar lobules V/VI (contrast estimate 0.672 [90% CI, 0.380, 0.964]), while decreased activity was seen in the cerebellar lobule VIIb (contrast estimate 0.787 [90% CI, 0.444, 1.130]) and in the middle frontal gyrus (contrast estimate 0.962 [90% CI, 0.557, 1.367]). These activations correlated with migraine disability (r = -0.46, p = 0.04) and motion sickness scores (r = 0.32, p = 0.04). We found enhanced connectivity between the pontine nuclei, cerebellar areas V/VI, and interior and superior occipital gyrus with numerous cortical areas in patients with migraine but not in controls. Migraine is related to abnormal modulation of visual motion stimuli within superior and inferior occipital gyrus, middle frontal gyrus, pontine nuclei, and cerebellar lobules V, VI, and VIIb. These abnormalities relate to migraine disability and motion sickness susceptibility.

Viewpoint oscillation improves the perception of distance travelled in static observers but not during treadmill walking

Optic flow has been found to be a significant cue for static observers’ perception of distance travelled. In previous research conducted in a large-scale immersive display (CAVE), adding viewpoint oscillations to a radial optic flow simulating forward self-motion was found to modulate this perception. In the present two experiments, we investigated (1) whether the improved distance travelled perceptions observed with an oscillating viewpoint in a CAVE were also obtained when the subjects were wearing a head mounted display (HMD, an Oculus Rift) and (2) whether the absence of viewpoint oscillations during treadmill walking was liable to affect the subjects’ perception of self-motion. In Experiment 1, static observers performed a distance travelled estimation task while facing either a purely linear visual simulation of self-motion (in depth) or the same flow in addition to viewpoint oscillations based on the subjects’ own head oscillations previously recorded during treadmill walking. Results show that the benefits of viewpoint oscillations observed in a CAVE persisted when the participants were wearing an HMD. In Experiment 2, participants had to carry out the same task while walking on a treadmill under two different visual conditions simulating self-motion in depth: the one with and the other without the visual consequences of their head translations. Results showed that viewpoint oscillations did not improve the accuracy of subjects’ distance travelled estimations. A comparison between the two experiments showed that adding internal dynamic information about actual self-motion to visual information did not allow participants better estimates.

Altered Insular and Occipital Responses to Simulated Vertical Self-Motion in Patients with Persistent Postural-Perceptual Dizziness.

Persistent postural-perceptual dizziness (PPPD) is a common functional vestibular disorder characterized by persistent symptoms of non-vertiginous dizziness and unsteadiness that are exacerbated by upright posture, self-motion, and exposure to complex or moving visual stimuli. Recent physiologic and neuroimaging data suggest that greater reliance on visual cues for postural control (as opposed to vestibular cues-a phenomenon termed visual dependence) and dysfunction in central visuo-vestibular networks may be important pathophysiologic mechanisms underlying PPPD. Dysfunctions are thought to involve insular regions that encode recognition of the visual effects of motion in the gravitational field. We tested for altered activity in vestibular and visual cortices during self-motion simulation obtained via a visual virtual-reality rollercoaster stimulation using functional magnetic resonance imaging in 15 patients with PPPD and 15 healthy controls (HCs). We compared between groups differences in brain responses to simulated displacements in vertical vs horizontal directions and correlated the difference in directional responses with dizziness handicap in patients with PPPD. HCs showed increased activity in the anterior bank of the central insular sulcus during vertical relative to horizontal motion, which was not seen in patients with PPPD. However, for the same comparison, dizziness handicap correlated positively with activity in the visual cortex (V1, V2, and V3) in patients with PPPD. We provide novel insight into the pathophysiologic mechanisms underlying PPPD, including functional alterations in brain processes that affect balance control and reweighting of space-motion inputs to favor visual cues. For patients with PPPD, difficulties using visual data to discern the effects of gravity on self-motion may adversely affect balance control, particularly for individuals who simultaneously rely too heavily on visual stimuli. In addition, increased activity in the visual cortex, which correlated with severity of dizziness handicap, may be a neural correlate of visual dependence.

OSCILLATORY OPTICAL FLOWS IMPROVE THE PERCEPTION OF TRAVELLED DISTANCE IN STATIC OBSERVERS

When static observers are exposed to a visual simulation of forward self-motion, they generally overestimate travelled distance relative to a previously seen distant target (Redlick, Harris, & Jenkin, 2001). Using the same experimental paradigm, we reproduced this result, which can be accounted for by a leaky path integration model (Lappe, Jenkin, & Harris, 2007). However, we also showed that a translational optical flow with additional oscillatory components, simulating head motion during walking, allows for better perception of travelled distance, as compared to a purely translational flow. This result can be discussed as an improvement of path integration, using an ecological optic flow pattern (close to natural walking feedback). In a subsequent experiment, we tested if it is the biological or the rhythmical nature of the simulation which provides better estimates of travelled distance. Participants were standing and passively confronted to three conditions of virtual simulation of self-motion in a 4-sided CAVE: (1) a translational optical flow (2) a translational flow, with an added component, via triangular oscillations in the vertical axis and (3) a flow, reproducing motion of the head during walking, as previously measured and modelled using a motion capture system. The results confirm that the addition of rhythmical components in the optic flow pattern improve the accuracy of travelled distance. However, they failed to reveal a significant difference between and rhythmic oscillations. Further experiments on the effect of spatio-temporal oscillatory components in the optical flow are required. However, these results can be related to recent studies comparing the effect of smooth and jittering optic flows on vection onset and strength (Palmisano et al., 2014). One suggestion is that oscillatory components produce a non-monotonous pattern of retinal motion, maintaining optimal sensitivity to optic flow, and consequently improving the perception of travelled distance. Meeting abstract presented at VSS 2016

Auditory self-motion simulation is facilitated by haptic and vibrational cues suggesting the possibility of actual motion

Sound fields rotating around stationary blindfolded listeners sometimes elicit auditory circular vection, the illusion that the listener is physically rotating. Experiment 1 investigated whether auditory circular vection depends on participants' situational awareness of “movability,” that is, whether they sense/know that actual motion is possible or not. While previous studies often seated participants on movable chairs to suspend the disbelief of self-motion, it has never been investigated whether this does, in fact, facilitate auditory vection. To this end, 23 blindfolded participants were seated on a hammock chair with their feet either on solid ground (“movement impossible”) or suspended (“movement possible”) while listening to individualized binaural recordings of two sound sources rotating synchronously at 60°/s. Although participants never physically moved, situational awareness of movability facilitated auditory vection. Moreover, adding slight vibrations like the ones resulting from actual chair rotation increased the frequency and intensity of vection. Experiment 2 extended these findings and showed that nonindividualized binaural recordings were as effective in inducing auditory circular vection as individualized recordings. These results have important implications both for our theoretical understanding of self-motion perception and for the applied field of self-motion simulations, where vibrations, nonindividualized binaural sound, and the cognitive/perceptual framework of movability can typically be provided at minimal cost and effort.

Absolute travel distance from optic flow

Optic flow fields provide rich information about the observer’s self-motion. Besides estimation of the direction of self-motion human observers are also able to discriminate the travel distances of two self-motion simulations. Recent studies have shown that observers estimate the simulated ego velocity of the self-motion simulation and integrate it over time. Thus, observers use a 3-D percept of the ego motion through the environment. In the present work we ask if human observers are able to use this 3-D percept of the motion simulation to build up an internal representation of travel distance and indicate it in a static scene. We visually simulated self-motion in different virtual environments and asked subjects to indicate the perceived distances in terms of static virtual intervals on the ground. The results show that human observers possess a static distance gauge, but that they undershoot the travel distances for short motion simulations. In further experiments we changed the modality of the distance indication but the undershoot in distance estimation remained. This suggests that the undershoot is linked to the perception of the optic flow field.

Simulation of self-motion in tethered flying insects: an optical flow field for locusts

A low-cost solution for a visual flow field device is described. The apparatus generates progressive and regressive patterns of motion with variable angular speeds and intensities. Additionally, rotational stimuli can be applied. First results show the efficiency of the flow field in producing flight behavior and steering responses in visual interneurons of locusts.