164｜Practice

Identification of brain regions associated withthe central and peripheral visual field andapplications for improving traffic safety
1. Background and goals
The perception and cognition of pedestrians appearing in the peripheral vision of drivers, and vice versa,
is essential to traffic safety. Therefore, studies of cognitive processing in central and peripheral vision areurgently needed to reduce traffic accidents.
The aim of this study was to make recommendations for the realization of traffic safety by revealing
the visual attributes that play important roles in human cognition and behavior.
1-1. Main study point
Three factors were the focus of this study: elderly individuals, intersections, and night-time.
Elderly individuals:
Intersections:Night-time:

the proportion of elderly individuals in fatal traffic accidents continues toincrease.
according to the study of traffic fatalities by road type, approximately half
the fatalities happen at the time of crossing streets or intersections.
the number of traffic fatalities peaks from dusk on into night-time.

The probability of traffic accidents will increase further when these factors are concurrently
present.
To investigate the correlation between the three factors and human visual function, special attention was paid to peripheral vision, because proper perception and cognition of pedestrians (automobiles) in the peripheral vision by drivers, and vice versa, will definitely improve traffic safety.
The functional properties of peripheral vision in humans have been investigated from the perspective of cognitive psychology but have yet to be fully elucidated. In addition, little information is available
on the central processing of visual information originating in the peripheral visual fields. In this study,
we therefore performed cognitive psychological experiments to investigate dynamic vision and theeffects of aging as well as neurological experiments to quantitate the cortical representation of peripheral
vision using functional magnetic resonance imaging (fMRI). The properties of a wide field of view andtraffic safety were also investigated.

Project Leader: Jinglong Wu
Professor, Graduate School of Natural Science and Technology, Okayama University

Identification of brain regions associated with the central and peripheral visual field and applications for improving traffic safety｜165

2. Research content
2-1. fMRI study on the physiological characteristics of a wide field of viewAfter developing a wide-field stimulus presentation device that operates under the MRI (high magneticfield) environment, fMRI was performed to reveal functional differences between central and peripheral
vision.
First, retinotopic mapping (functional mapping of the visual cortex)(1)and quantitative analysis of central
and peripheral vision were performed.
Conventionally, it has been possible toexamine only up to 60 degrees ofvisual angle due to the limitations ofBrainMRI撮像領域
area scanned in MRI
MRI session
MRI実験風景

4040度
degrees 8080度
degrees

120120度
degrees

temporal resolution in fMRI. Therefore, to perform this experiment, wedeveloped a new stimulus presentation
Stimulationof central and peripheral vision
中心・周辺視野の刺激
device that enables the mapping of up
Figure 1. Imaging device and technique for cortical representation of
to 120 degrees of visual field. As athe visual field
result, we could confirm that a diffuse
area adjacent to the occipital lobe was the brain region involved in the processing of peripheral vision.
Use of the device, with its wider field of visual stimulation, further revealed that this diffuse area wasmore extensive than previously studies have reported.
Quantitative analysis showed that the size of the brain area involved in information processing
decreases as the visual field nears the far periphery. Furthermore, the study of the temporal frequency
response properties of central and peripheral vision showed that the maximum response was elicited bya temporal stimulation frequency of 4 Hz when the eccentricity was 20 degrees (central visual field) (1)and by temporal frequencies of 4–8 Hz when the eccentricity was 40 degrees (2), but only small differences were observed in the responses to individual frequencies when the eccentricity was 60 degrees(peripheral visual field) (3).
2-2. Cognitive psychological study on the characteristics of wide field of view
A conventional manual device to measure dynamic visual field was automated to quantitatively analyze
the dependency of dynamic visual field on brightness and color. Differences in dynamic visual field
between young and elderly individuals were also measured and analyzed. Further, we modified the light(1) Retinotopy: Using a similar principle as in cameras, light information from an object is projected onto the retina, where it is converted into electrical signals by photoreceptors. In this process, spatial information in the retina is maintained in the visual cortex in thebrain. For example, information from the center of the retina is sent to the posterior of the visual cortex, while more anterior regions of
the visual cortex process information originating from more peripheral locations of the retina. Such reconstruction of spatial information in the retina by the visual cortex is called retinotopy.

166｜Practicesource in the measurement
device, which allowed us toMeasurement of dynamic
visual field

Setting the direction of visual targets
12 longitudinal directions

quantitate the dependency ofdynamic visual field on bright-135°

45°
30°

150°

ness and color, and to investigate how aging affects the165°

dependency.
Dynamic visual field isdefined as a visual range within

15°
5°

180°

345°

195°
210°

which humans are able todiscriminate a moving object.
Dynamic visual field is particularly important when driving or

120° 115° 90° 75° 60°

330°
315°

225°
240° 255° 270° 285° 300°

Figure 2. Development and use of a dynamic visual fieldmeasurement device

crossing streets. In this study, the Goldmann perimeter was remodeled to be functionally flexible andmore accurate. Underestimation of dynamic visual field by subjects is a serious problem, especially whenstudies involve fast-moving visual targets or elderly individuals with slow reaction speeds. In this study,
we therefore measured the response time of subjects under different condition to correct for thisunderestimation.
Subjects were 5 individuals aged 20–23 years, 9 individuals aged 50–64 years, 4 elderly individuals
aged 65–74 years, and 4 elderly individuals aged 75–80 years. Subjects were instructed to stare at thecenter of the screen and push a button as soon as they notice a target moving inward from the peripheryat a given constant speed. Results indicated that dynamic visual field was relatively wider in younger
individuals than in elderly individuals. With regard to speed dependency, all age groups had a tendency
to decrease slightly as the speed of the target increased. The visual field in elderly individuals aged 75–80
years was approximately half the visual field in individuals in their 20s, revealing a marked effect ofaging. However, dynamic visual field was not lost evenly in an age-dependent manner, and dynamic
visual field instead varied greatly among individuals.
2-3. Investigation of the association between wide field of view and traffic safety
We plan to apply the findings of this study to improve traffic safety and recommend the revision of roadsign installation criteria and of regulation for traffic safety education aimed at elderly people.

Identification of brain regions associated with the central and peripheral visual field and applications for improving traffic safety｜167

Visual characteristics in elderly individuals
and traffic accidents
Peripheral visual informationin traffic environments
Road traffic information
Various hazardous events

Functional limitations in vision
Cortical representation of peripheral vision
Effects of aging on vision
Loss of dynamic vision
Effects of aging on cognitive function
Delay in information processing, action-taking, and related processes

Reduced traffic information from peripheral vision
Ignored traffic laws Delayed risk avoidance

Recommendations toimprove traffic safety■Establishment of senior-friendly trafficenvironments■Road designs and automotive equipment parts
that take account of peripheral visual acuity
and cognitive function■Avoiding unseen situations■Making things easily visible■Supporting invisible parts■Traffic safety education of elderly individuals■Incorporation of visual field testing into official
driver’s training sessions

Traffic accident
Figure 3. Recommendations to improve traffic safety based on the relation between visual characteristics
in elderly individuals and traffic accidents

3. Conclusions
Through the investigation of central and peripheral vision in humans, we were able to reveal under whatcircumstances peripheral visual acuity was compromised. The effect of aging on dynamic visual field
was substantial, particularly among elderly individuals aged 75–80 years because of severely impaired
cognition of moving objects in peripheral vision.
In retinotopic mapping, the central information processing area for peripheral vision was narrowcompared with central vision. Furthermore, the study of brain activity in response to temporal frequencies showed that the maximum response was elicited by a temporal stimulation frequency of 4 Hz whenthe eccentricity was 20 degrees (central visual field) (1) and by temporal frequencies of 4–8 Hz when theeccentricity was 40 degrees (2), but only small differences were observed in the responses to individual
frequencies when the eccentricity was 60 degrees (peripheral visual field) (3).

4. Future outlook
When moving on a street (including driving), we sense and process environmental signals before taking
proper actions. To act safely, it is necessary to accurately execute the 3 stages of information processing—perception, cognition, and action—and as the organ that governs these functions, the brain should
be investigated to reduce traffic accidents. In this study, to recommend traffic safety measures, special
attention was paid to intersections and to elderly individuals, who are highly associated with traffic accidents, to investigate the brain function involved in wide-field visual acuity and the effects of aging on
dynamic vision. It is important to continue basic research with emphasis on the central mechanisms
involved in perception, cognition, and action in order to reduce the number of traffic accidents in thefuture.