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Thomas Stephan Heinrich, Michael Bach; Contrast Adaptation in Human Retina and Cortex. Invest. Ophthalmol. Vis. Sci. 2001;42(11):2721-2727.
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© ARVO (1962-2015); The Authors (2016-present)
purpose. Although cortical contrast adaptation has been extensively studied with
both psychophysical and electrophysiological techniques, little is
known about retinal contrast adaptation in humans.
methods. Retinal and cortical long-term contrast adaptation was assessed with
simultaneous measurement of pattern electroretinogram (PERG) and
cortical visual evoked potentials (VEPs). This study involved three
approaches: sampling of the contrast transfer function from 2.7% to
98% with adaptation to high (98%) and low (7.3%) contrasts,
linearity of adaptation effects, and transfer of contrast adaptation
between parallel and orthogonal grating orientations.
results. Contrast adaptation affected retinal and cortical recordings quite
differently. The VEP showed a sigmoid contrast transfer function, which
was shifted toward higher contrasts (by a factor of 1.9), whereas
amplitudes at higher test contrasts were enhanced to 127%. The PERG
decreased in amplitude to approximately 90%, and the latency was
significantly reduced by 4 to 6 msec (P < 0.05).
All measured effects were linear with adaptation contrast. Orientation
played no role in the PERG results, whereas the VEP was enhanced to
125% when tested parallel and to 150% when tested orthogonal to
conclusions. VEP results confirm and extend previous findings and fit well with
single-cell recordings. The PERG findings suggest that retinal contrast
adaptation occurs and mainly operates in the temporal domain,
comparable to rapid gain–control findings in cats and
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