Improvement in human vision under bright light: grain or gain?
1. The factor by which increment threshold changes with changing background intensity is less if the test flash is small than if it is large. This is commonly attributed to a reduction of the area over which visual signals are integrated as light adaptation increases. 2. We propose and test an alter...
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Published in | The Journal of physiology Vol. 394; no. 1; pp. 41 - 66 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Oxford
The Physiological Society
01.12.1987
Blackwell |
Subjects | |
Online Access | Get full text |
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Summary: | 1. The factor by which increment threshold changes with changing background intensity is less if the test flash is small than
if it is large. This is commonly attributed to a reduction of the area over which visual signals are integrated as light adaptation
increases. 2. We propose and test an alternative hypothesis that the change in slope is the result of purely local processes:
if it is assumed that increasing the background intensity increases the exponent of the local response function, but does
not alter the extent of spatial integration, then the threshold of the small test flash will rise more slowly than the threshold
of the large test flash simply because the small test flash is of a higher intensity than the large and therefore evokes a
correspondingly greater local response. 3. We measured small and large test field increment thresholds and dichoptic brightness
matches as a function of background intensity. 4. The log-log slopes of the small and large field increment threshold functions
differed by not more than about 20%, suggesting that even under the conventional interpretation of such data, the change of
spatial integration is less than is usually supposed. 5. The intensity of a large (2.3 deg) suprathreshold test field matched
to a standard in the other eye varies with increasing background intensity with the same shallow slope as the small test (2.6
min) threshold versus intensity function; this is in agreement with the predictions of the local non-linearity hypothesis
and suggests that there is no substantial change in spatial integration during light adaptation. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/jphysiol.1987.sp016859 |