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Titolo:
Motion detection from photopic to low scotopic luminance levels
Autore:
van de Grind, WA; Koenderink, JJ; van Doorn, AJ;
Indirizzi:
Univ Utrecht, Helmholtz Inst, Utrecht, Netherlands Univ Utrecht Utrecht Netherlands , Helmholtz Inst, Utrecht, Netherlands Univ Utrecht, Dept Comparat Physiol, NL-3584 CH Utrecht, Netherlands Univ Utrecht Utrecht Netherlands NL-3584 CH 3584 CH Utrecht, Netherlands Univ Utrecht, Buys Ballot Lab, Dept Phys Man, NL-3584 CC Utrecht, Netherlands Univ Utrecht Utrecht Netherlands NL-3584 CC 3584 CC Utrecht, Netherlands
Titolo Testata:
VISION RESEARCH
fascicolo: 2, volume: 40, anno: 2000,
pagine: 187 - 199
SICI:
0042-6989(2000)40:2<187:MDFPTL>2.0.ZU;2-0
Fonte:
ISI
Lingua:
ENG
Soggetto:
MONOCULAR VISUAL-FIELD; SPATIAL WHITE NOISE; RANDOM-DOT PATTERNS; CONTRAST; DETECTABILITY; MOVEMENT;
Keywords:
motion detection; photopic; scotopic; luminance levels;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
28
Recensione:
Indirizzi per estratti:
Indirizzo: van de Grind, WA Univ Utrecht, Helmholtz Inst, Utrecht, Netherlands Univ Utrecht Utrecht Netherlands Utrecht, Netherlands
Citazione:
W.A. van de Grind et al., "Motion detection from photopic to low scotopic luminance levels", VISION RES, 40(2), 2000, pp. 187-199

Abstract

In this study we quantify the influence of adaptation luminance on the threshold for direction-detection in coherently moving random-pixel arrays (RPAs). Square RPAs of a constant rms-contrast (35%) were used and we determined their 'critical' or threshold-width W-c. Mean retinal illuminances were varied in 13 steps of 0.5 log unit from the low photopic range (screen luminance 0.3 cd/m(2)) down to 6 log units attenuation, which appeared to be about the absolute threshold of vision under the conditions of our experiment. Moving RPAs were presented at six retinal locations (0, 3, 6, 12, 24 and 48 degrees) from the fovea to the far periphery in the temporal visual field of the right eye of three experienced observers (the authors). In order to ensure an honest comparison between these very disparate conditions, the spatial dimensions (including speed) were scaled according to the acuity, as measured separately for each of the viewing-conditions and observers. Acuity scaling proves to equate the performance for all eccentricities and luminance levels rather well. The fovea is special, but only in the sense thatthe absolute threshold for light detection is reached earlier than in peripheral regions. In all other respects foveal results follow the pattern found for peripheral locations. Two different regimes can be discerned in the data? one for high and one for low speeds. In the low speed range W-c is almost constant, regardless of luminance level or eccentricity. The critical 'crossing-time' T-c for any pixel starting at one end of the stimulus and leaving at the opposite end is therefore inversely proportional to velocity in the low-speed range (time-velocity reciprocity). At medium-to-high speeds W-c increases linearly with velocity. so T-c is constant. This constant (minimum) value of T-c differs between subjects, but in all subjects it increases somewhat with decreasing luminance level, even for our acuity-scaled stimuli. The different behaviour for low and high speeds [reported before for photopic viewing conditions by van de Grind, W. A.. van Doom. A. J., & Koenderink, J. J. (1983. Journal of the Optical Society of America, 73, 1674-1683) and van de Grind, W. A., Koenderink, J. J., & van Doorn A. J. (1986. Vision Research, 26, 797-810)] proves to hold from photopic to low scotopic luminance ranges, provided the stimuli are scaled according to acuity. Wedraw the general conclusion that movement detection is a very robust process that tolerates extremely low retinal illuminance levels. Moreover, the visual system appears to use the same processing principles in combination with an acuity-scaled architecture under all adaptation states and at all eccentricities. (C) 2000 Elsevier Science Ltd. All rights reserved.

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Documento generato il 26/09/20 alle ore 14:35:36