別紙41 (課程博士(英文))Date of submission (month day, yeal')
Depadmentofcomputer
StudenuDNumber

Science and Engineering

January loth,2020

D133337
Supervisors

Sh喰ekiNakauchi
Tetsuto Minami

PP11Canfs nameYuta suzuki

Abst"act (Docto")
Title oflhesis

Investigation ofthe neural mechanisms in i11Usory glare pel'ception

Approx.80o words
The perceived intensiw of light coming 丘'om a given portion of an object (brightness) and the perceptual experiences
Of a black, gey, or white・C010red surface and self・1Uminosity (1igh加ess) are some of the basic aspects of visualProcessing. Glare i11Usion,、vhich is an opticali11Usion, enhances the perceived brightness of a central white area
Surrounded by a 1醐】inance gradient without any actual change in lioht intensity. our experiences of perceptual

misunderstanding are sometimes caused by opticaliⅡUsions that create visualimages that may carry deceptiveinterpretations. Although it seems that opticali11Usions trick our brains into believino things that may or may not bereal,they demonstrate how the brain makesthe most probable prediction about an amb地Uous visualinput. This is not aretina・1evel process, but a serial processing occuning in the bl'ain,、vhich is valuable for understanding how the brain
interprets visualstimuli 介om the extemal world.

The pupiⅡary response is mainly a function of l'etinali11Uminance owing to the amount of li8ht energy orquanta entering the eye 介om the ambient environment. Although one ofthe main functions of pupil constriction

Would seem to be the pl'otection of our eyes from being dazzled by intense physica11ight, previous studies using
Pupi110metry have revealed that the pupilis also constricted by the pel'ceived intensity of light in the absence ofany change in light intensiw via glare i11Usion. Because the visual system processes luminance infonηation froma graphicalimage as ifit 、Nere a natural scene, C010rs could play an imp011ant role in the perception ofbriohtness.
In this study, we flrst examined 、vhether pupil constrictions to glare i11Usion are stronger for blue compal・ed to
Other c010rs. our results indicate that blue 、vas subjectively evaluated by pa11icipants as the brightest condition,
despite aⅡ C010red stimuli being equiluminant. Moreover, glare・related pupil constrictions for each participant
Were correlated to each individual's subjective brlghtness adjustments. Together, these 6ndinos show that

PupiⅡometry constitutes an easy toolto assess individual diffel'ences in c010r briohtness perception
Second,、¥e tested the hypothesis thatthe ec010gical background, where getting dazzled by light is common
When one directly looks at sunlight through some occluders, can explain the larger pupil constriction to blue.
Interestingly, we found the effect of blue on pupi11ary constriction occurs only for people with blaclvbro、Nn iris

C010rs. Because the iris c010r relates to tlw macular pigment densiw as a marker for the adaptation to thehomogeneous environment, we assumed that the pupiⅡary constriction represents the adaptation response to a
Probable dazzling sun1喰htimitated by glare iⅡUsion, and the pupil constriction m喰ht be similarto the function ofmacular pigments t0 負lter the blue light pl'ojecting to the retina.
Next, we exalnined two probable factors to modulate the pupil size in glare i11Usion by usino the Kanizsa

triangle with a radial pattern ofluminance gradation and a control pattern.、Ne assumed thatthe pupil constriction
to glare i11Usion represents:(a)血e role of 'anticipation' or 'preparation' to probable glare situation from the sun

Or scattering light, and (b) the localized stimulus pattern because the avera8ed luminance of the glare iⅡUsion
Within a smaⅡ Visual aeld is h地her than its control condition, where the rotated luminance gradient pa廿ern. ourresults show a larger pupil constriction effect on the Kanizsa triangle with the radial patrem; therefore, weConclude that the pupil constriction to glare i11Usion is prompted by self・1Uminosity perception.1he e仟ect ofthebrightness judgment on pupil response shown in pNvious works is considered additionaⅡy to the e仟ect of'self・1Uminosity'to the brightness perception but via difference pathway from surface c010r perception.
＼ve subsequenuy investigated the correlation bet、veen pupil constriction and electl'oencephalography (EEG)

response of the amplitude of the steady・state visual evoked potential (SSVEP) on the i11Usory bri8htness
enhancement with glare i11Usion. we found that the ssvEp amplitude was lower in glare iⅡUsion than in theControl condition (no glal'e condition), especiaⅡy under high luminance contrast conditions. The probable
Correlation ofthe inhibited ssvEp amP1北Ude to the high luminance contrast ofσlare 川Usion accompanied by thegreater puPⅡ Constriction may be because of the decreased amount of light entering the pupil. Thel'efore, thebrightness enh即Cement in the glare iⅡUsion is already represented at the prima1シ Stage of visual processino
Iinked to the larger pupil constriction.

As a condusion, we have put together the evidence of the largel' pupil constl'iction e行'ect on glare i11Usion
that carl be ele8anuy explained by the ec010gy of vision that the laroe pupil constriction on the i11Usory olare
Perception may be a prediction of the probable strong light, especia11y for blue, sky・1ike, glare 淵Usion makes
more po、¥erful e仟ect in causing constrictions.