Dynamic shifts of the contrast-response function.

TitleDynamic shifts of the contrast-response function.
Publication TypeJournal Article
Year of Publication1997
AuthorsVictor, J D., Conte M M., and Purpura K P.
JournalVis Neurosci
Date Published1997 May-Jun
KeywordsAdaptation, Physiological, Contrast Sensitivity, Evoked Potentials, Visual, Humans, Photic Stimulation

We recorded visual evoked potentials in response to square-wave contrast-reversal checkerboards undergoing a transition in the mean contrast level. Checkerboards were modulated at 4.22 Hz (8.45-Hz reversal rate). After each set of 16 cycles of reversals, stimulus contrast abruptly switched between a "high" contrast level (0.06 to 1.0) to a "low" contrast level (0.03 to 0.5). Higher contrasts attenuated responses to lower contrasts by up to a factor of 2 during the period immediately following the contrast change. Contrast-response functions derived from the initial second following a conditioning contrast shifted by a factor of 2-4 along the contrast axis. For low-contrast stimuli, response phase was an advancing function of the contrast level in the immediately preceding second. For high-contrast stimuli, response phase was independent of the prior contrast history. Steady stimulation for periods as long as 1 min produced only minor effects on response amplitude, and no detectable effects on response phase. These observations delineate the dynamics of a contrast gain control in human vision.

Alternate JournalVis. Neurosci.
PubMed ID9194324
Grant ListEY7977 / EY / NEI NIH HHS / United States

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