Red: activated regions showing the interaction between pillar and target position. Blue: regions commonly activated in all four conditions including speed and types of the pillar in the analysis of brain activity related to the relative amount of upward OF normalized in each condition when the target was presented at the far-right position Table 5.
Green: regions commonly activated in all four conditions in analysis of brain activity related to the amount of upward OF normalized across all four conditions when the target was presented at the far-right position Supplementary Table S1.
Results of functional magnetic resonance imaging of anatomical regions, peak voxel coordinates, t -values for activations related to a relative change in the amount of upward optic flow normalized in each condition that is common in all speed and pillar conditions.
Next, we examined the brain activity related to changes in the amount of upward OF with the regressor Z-score normalized across four sessions. However, there was no significant main effect of speed in the precuneus region, indicating that the precuneus would be active irrespective of speed when the upward OF was elicited.
However, activations that were common across all conditions in the left middle temporal cortex, left precentral gyrus, left lingual gyrus, cerebellum, right superior temporal gyrus, right inferior parietal lobule, left central and frontal operculum, and left opercular part of the inferior frontal gyrus overlapped with those obtained using the upward OF regressor Z-score normalized in each session Supplementary Table S7.
The cluster in the parietal cortex, including the precuneus, was close to the activated region when the target was presented at the far-right position in the tilted pillar condition see Figure 8B for overlap. However, we observed no upward OF-related brain responses indicating a significant main effect of pillar or interaction. Results of functional magnetic resonance imaging of anatomical regions, peak voxel coordinates, and F -values for activations related to the amount of upward optic flow normalized across all four conditions when the target was presented at the far-right position showing the main effect of speed.
Finally, when we compare the resultant contrast map with the activation for the target onset at the far-right position specifically in the tilted pillar condition, there was a notable overlap in the precuneus within the left parieto-occipital cluster Supplementary Table S8 and Supplementary Figure S3. Therefore, the precuneus activity was not simply explained by the target detection, instead, it was confirmed that the additional activation in the precuneus region is likely associated with the extraneous-OF.
As predicted, the RTs for detection of the target were influenced by the type of the windshield, namely the angle of the pillar. The RT was longer with the tilted pillar than with the vertical pillar when detecting a target presented at the far-right and far-left positions.
Our fMRI analyses suggested that the activity in the precuneus was possibly related to the excessive OF along a pillar that may lead to additional attentional load. At the slow speed, the upward extraneous-OF was observed more along the tilted pillar than along the vertical pillar in most of the cases of areas and angles. At the fast speed, the tilted pillar elicited more upward extraneous-OF with relatively small angles to the pillar than the vertical pillar.
This suggests that an OF with a large angle e. At the fast speed, the total OFs increase, thereby the upward extraneous-OF with a relatively large angle to the tilted pillar decreased by the subtraction of the upward OF on the side without a pillar. These results suggest that upward extraneous-OF with relatively small angles to the pillar was the most pronounced.
The mechanism accounting for this finding might be the same as that with the barber pole illusion Wallach, whereby an oblique grating moving horizontally behind an elongated rectangular aperture leads to an illusory perception of upward motion along the major axis of the aperture.
Given that actual OFs in a driving scene intersect with smaller angles to the tilted pillar than to the vertical pillar, this could result in more OFs intersecting obliquely with the tilted pillar than with the vertical pillar, leading to a situation similar to that of the barber pole illusion. Therefore, it was speculated that illusory perception of upward motion, which has a small angle to the pillar, could occur around the tilted pillar. This upward OF is almost in parallel to the pillar, a large object e.
Nevertheless, it is known that the spatial resolution of our peripheral vision is lower than that of the foveal vision. Since the area of consideration here at pixels equivalent to 0.
To note, the effect of speed was more dominant for the amount of upward OF than the angle of the pillar. Nevertheless, the type of pillar did affect the amount of upward OF. Because the primary purpose of this study was to examine the influence of the windshield and its pillar for the application of vehicle designing, we focused primarily on the difference between the tilted and vertical pillars.
The results of OF analysis suggested that there were considerable differences in OF between the two types of the windshield and that it would be plausible that the extraneous-OF especially at around the pillar could distract attention during driving. Given the assumption that OF may diminish attentional performance around the pillar, we conducted a visual target-detection task.
Focused analysis of the RT for detection of the target at the far-left and far-right positions, which were equidistant from the fixation point, indicated that the RT was longer when a target appeared near to the pillar far-right than when it was presented far from the pillar far-left. However, human spatial attention is reportedly better in the left visual field than in the right visual field due to the hemispherically specific role of visuospatial attention in the right hemisphere Pouget and Driver, ; Rees et al.
This could prompt speculation about our findings because the pillar was only placed within the right visual hemifield; however, a direct comparison between the right and left visual field conditions suggests that this might not be the case. In the comparison of mean RTs focused on the far-most target positions far-left, far-right , the tilted pillar tends to slow the RT more than the vertical pillar irrespective of visual hemifield see Figure 6.
These results suggest that excessive induction of OF along the pillar might impede the instantaneous detection of a target. The distance at the far-right target position for the tilted pillar was within 10 pixels seven pixels corresponding to 0. A careful investigation may be necessary to reveal as to how the distance between the target and the pillar impact on RT and brain activity for target detection in a future study.
Moreover, the main effect of speed on the RT was more dominant than the angle of the pillar. Since we did not observe any interaction of speed with target position and pillar, the effect of speed was common in all target positions and all pillar types.
Therefore, our result suggests that the effect of speed is not related to the existence of the pillar that we focused on in the present study. In the fMRI analysis, we observed that the precuneus was activated when the target was presented at the far-right position on the windshield with a tilted pillar, in which the RT for target detection was increased. Given the finding that more upward OFs were elicited in the windshield with a tilted pillar than in the one with a vertical pillar, increased activation in the precuneus may be involved in the slowed RTs putatively caused by upward extraneous-OF.
The precuneus has been reported to be fundamental to attentional functions. Simon et al. Several studies have suggested that the precuneus is involved in attentional shift Le et al. It has also been reported that the precuneus is activated in tasks involving covert shifts of spatial attention Gitelman et al.
In contrast, abnormal activation in the precuneus is thought to be related to attention deficit hyperactivity disorder, implying a deficit in sustained attention Castellanos et al. In the present study, we observed increased activation in the precuneus related to the detection of a target around the tilted pillar. In the windshield with a tilted pillar, the extraneous-OF was elicited irrespective of the speed revealed by OF analysis in Experiment 1.
These results may reflect a redundant attentional shift for target detection presented around the tilted pillar. However, there could be another interpretation of the precuneus activity that reflected the saccadic effects since the subjects might suppress the urge to look towards the target. This view is supported by the previous research showing that the frontoparietal areas including the precuneus are involved in saccadic suppression Brown et al.
However, this possibility might be ruled out by the fact that the precuneus was active more for the far-right target detection than for the far-left target detection in the tilted pillar condition while the saccadic effect would be same for the far-left and far-right targets that are in the equidistance to the fixation cross. Thus, this result would provide the support that the precuneus reflected the extraneous-OF elicited around the tilted pillar near the far-right target that accompanies a subtle impact on visual attention.
To examine whether the relative change in upward OF for each speed and pillar condition affected brain activity, we first examined the upward OF-related brain activation using the upward OF regressor Z-score normalized in each session.
This revealed that brain activity was related to upward OF when the participants detected the target presented at the far-right position in the left middle temporal area, premotor areas, and the bilateral and medial parietal areas including the precuneus.
This suggests the perception of OFs created by micro-flows of visual fractions recruits brain regions responsible for the detection of motion, while a salient distinct object is not necessarily moving.
To detect the target presented at the far-right position, the participants had to shift their attention to the right peripheral visual field. Therefore, it is reasonable that activation in the middle temporal area might be lateralized to the left. Furthermore, activation in the left motor cortices could be caused by the motor response to the target using their right hand. More interestingly, the activated cluster related to the upward OF in the precuneus partly overlapped with that showed activation related to the target detection presented at the far-right position in the windshield with a tilted pillar see Figure 8B.
The second analysis using the upward OF regressor that was Z-score normalized across four sessions revealed that activity in the precuneus did not show the main effect of speed. This finding suggests that the precuneus was active irrespective of the speed, which co-varied with the absolute amount of upward OF. Therefore, the precuneus activity for the target detection of the far-right position where the upward OF was the most prominent was not influenced by the absolute amount of upward OF, but by the relative amount of upward OF in a particular speed-and-pillar condition.
Overall, these observations suggest that the upward OF might be related to additional attentional load, which might invoke activations in the precuneus. This is certainly a limitation of the current study. Our neurobehavioral results provide quantitative evidence that supports the validity of evaluation based on the attentional loading of the driver when assessing visibility through a windshield. However, the sample size of this study 35 subjects is relatively small for an fMRI study for generalization.
In the present study, we determined the shape and angles of the pillar based on the actual vehicle in production. However, it is possible that the various parameters, such as the width of the pillar, would affect the results. Furthermore, only one angle of tilt was examined in this study. To apply our results to the design of vehicles, systematic variations of the parameters of the shape of a pillar and windshield may be needed in future studies. More importantly, the experimental environment in the MRI scanner is markedly different from the actual driving environment because of constraints in MRI measurement, such as posture in the scanner and the view through the small mirror attached to the head coil in front of the participant.
Measurements of brain activity when subjects are driving a real vehicle using wearable brain imaging techniques, such as electroencephalography, may be necessary e. Moreover, our experiment focused on a simple situation in which a vehicle was traveling straight in one direction. Examinations in other driving situations, e. We have found that activation in the precuneus is associated with an increased RT for the detection of a target on a windshield with a tilted pillar.
The precuneus activation for detection of the target presented outside the tilted pillar in the periphery was also influenced by the relative change in extraneous-OF in the visual field. These results provide behavioral and neuroscientific evidence that the task driving -irrelevant OFs along the pillar are responsible for the excessive attentional shift. Finally, our study was a neuroscientific investigation that provides rich insights for the design of safe vehicles, at least for the windshield.
The studies involving human participants were reviewed and approved by Research Ethics Committee of Hiroshima University. TS and YO performed the experiments and analyzed the data.
TY contributed to the OF analysis. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We are grateful to Dr. Noriaki Kanayama and Dr. Kai Makita for helpful discussions concerning this study and Dr. Syoichi Shiota for assistance with the implementation of the experiment. We would like to thank Editage www. National Center for Biotechnology Information , U. Journal List Front Hum Neurosci v. Front Hum Neurosci. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. Screenshot of the Week.
Submit your photo Hall of fame. Featured on Meta. Now live: A fully responsive profile. Screenshot of Week 51 [Submissions Closed]. Linked Related 8. Hot Network Questions. I had a concussion from having the kid in back slam into my head. But I believe one of the kids did die later on. I suppose that with a few more mph I would have hit the windshield. I had that tooth reimplanted, and it lasted until earlier this year.
Someone clearly needs to get Mythbusters on the case. People think that by installing bigger brakes on their cars they will brake in shorter distance but they do not realize that even the stock brakes can exert much greater than the required force and the actual weakest link is the tires.
Like you said, normal cars on high performance street tires can do about 1g max. Lightweight cars like Caterham, Ariel Atom etc can do about 1. Mercedes Benz has developed an experimental airbag-like device that deploys when a colision is imminent, somewhere between the front of the car and the road surface. This, combined with the normal brakes, can generate up to 2g of braking force. Actually, the car has nothing to do with it. Say you weigh lbs. During a rollover, the windshield is providing up to 60 percent of the strength that is needed to keep your roof from falling.
In other words, it is absorbing the force of the collision, instead of you absorbing it. The windshield was specially designed to keep the roof from crushing you, as well as keep the bugs off your face!
Your windshield is an important barrier that keeps you in the car. According to independent testing, over 70 percent of the windshields in the United States are replaced incorrectly.
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