scholarly journals Four days of visual contrast adaptation: effects on perceived contrast grow monotonically while effects on orientation rise then fall.

2014 ◽  
Vol 14 (10) ◽  
pp. 400-400
Author(s):  
E. Fast ◽  
K. Haak ◽  
M. Bao ◽  
S. A. Engel
Keyword(s):  
Visual Contrast ◽  
Contrast Adaptation ◽  
Adaptation Effects

Spatial Frequency-Specific Contrast Adaptation Originates in the Primary Visual Cortex

2007 ◽  
Vol 98 (1) ◽  
pp. 187-195 ◽  
Author(s):  
Thang Duong ◽  
Ralph D. Freeman
Keyword(s):  
Visual Cortex ◽  
Spatial Frequency ◽  
Frequency Tuning ◽  
Adaptation Effect ◽  
Tuning Curves ◽  
Contrast Adaptation ◽  
Spatial Frequencies ◽  
Neurophysiological Studies ◽  
High Contrast Grating ◽  
Adaptation Effects

Adaptation to a high-contrast grating stimulus causes reduced sensitivity to subsequent presentation of a visual stimulus with similar spatial characteristics. This behavioral finding has been attributed by neurophysiological studies to processes within the visual cortex. However, some evidence indicates that contrast adaptation phenomena are also found in early visual pathways. Adaptation effects have been reported in retina and lateral geniculation nucleus (LGN). It is possible that these early pathways could be the physiological origin of the cortical adaptation effect. To study this, we recorded from single neurons in the cat's LGN. We find that contrast adaptation in the LGN, unlike that in the visual cortex, is not spatial frequency specific, i.e., adaptation effects apply to a broad range of spatial frequencies. In addition, aside from the amplitude attenuation, the shape of spatial frequency tuning curves of LGN cells is not affected by contrast adaptation. Again, these findings are unlike those found for cells in the visual cortex. Together, these results demonstrate that pattern specific contrast adaptation is a cortical process.

scholarly journals Abnormal Adaptation of Visual Contrast Sensitivity In Multiple Sclerosis Patients

1981 ◽  
Vol 8 (3) ◽  
pp. 227-234 ◽  
Author(s):  
J. Raymond ◽  
D. Regan ◽  
T.J. Murray
Keyword(s):  
Multiple Sclerosis ◽  
Contrast Sensitivity ◽  
Test Procedure ◽  
Acute Stage ◽  
Visual Contrast ◽  
Contrast Adaptation ◽  
Spatial Frequencies ◽  
Permanent Loss ◽  
Multiple Sclerosis Patients ◽  
Visual Contrast Sensitivity

SUMMARY:Some multiple sclerosis patients with 20/20 acuity complain of poor vision. In a previous report we accounted for this in our patient group by showing that multiple sclerosis had caused a depression of contrast sensitivity while sparing visual acuity. In this study we investigated whether some of this measured depression might be due to abnormally rapid or severe adaptation during the test procedure rather than a true permanent loss. Our finding was opposite to this supposition: adaptation was abnormally slight and/ or slow.Depressed contrast sensitivity was not well correlated with abnormal adaptation to contrast. In patients whose contrast sensitivity losses were restricted to a band of spatial frequencies, we found no evidence that abnormalities of contrast adaptation were restricted to this same spatial frequency band. Further evidence of dissociation between abnormal contrast sensitivity and abnormal contrast adaptation is that some patients with normal contrast sensitivity showed abnormally small adaptation.Our finding of abnormally slow or abnormally small contrast adaptation in MS patients seems to conflict with Enoch et al’s (1978) report of abnormally great adaptation after inspecting a bright stimulus. This apparent disagreement may be due to their use of prior dark adaptation, very bright adapting stimuli and patients in the acute stage of retrobulbar neuritis.

Modeling Visual Cortical Contrast Adaptation Effects

1997 ◽  
pp. 525-531 ◽  
Author(s):  
E. V. Todorov ◽  
A. G. Siapas ◽  
D. C. Somers ◽  
S. B. Nelson
Keyword(s):  
Contrast Adaptation ◽  
Visual Cortical ◽  
Adaptation Effects
Sign in / Sign up

Export Citation Format

Share Document