We measured reaction times for detecting the onset of motion of sinusoidal gratings of 1 c/deg, modulated in either luminance or chromatic contrast, caused to move abruptly at speeds ranging from 0.25 to 10 deg/s (0.25–10 Hz). At any given luminance or chromatic contrast, RTs varied linearly with temporal periodicity (r2≅0.97), yielding a Weber fraction of period. The value of the Weber fraction varied inversely with contrast, differently for luminance and chromatic contrast. The results were well simulated with a simple model that accumulated change in contrast over time until a critical threshold had been reached. Two crucial aspects of the model are a second-stage temporal integration mechanism, capable of accumulating information for periods of up to 2 s, and contrast gain control, different for luminance than for chromatic stimuli. The contrast response for luminance shows very low semi-saturating contrasts and high gain, similar to LGN M-cells and cells in MT; that for colour shows high semi-saturating contrasts and low gain, similar to LGN P-cells. The results suggest that motion onset for luminance and chromatic gratings are detected by different mechanisms, probably by the magno- and parvo-cellular systems.

Dependency of reaction times to motion onset on luminance and chromatic contrast / David C. Burr; Beatrice Corsale. - In: VISION RESEARCH. - ISSN 0042-6989. - STAMPA. - 41:(2001), pp. 1039-1048.

Dependency of reaction times to motion onset on luminance and chromatic contrast

BURR, DAVID CHARLES;
2001

Abstract

We measured reaction times for detecting the onset of motion of sinusoidal gratings of 1 c/deg, modulated in either luminance or chromatic contrast, caused to move abruptly at speeds ranging from 0.25 to 10 deg/s (0.25–10 Hz). At any given luminance or chromatic contrast, RTs varied linearly with temporal periodicity (r2≅0.97), yielding a Weber fraction of period. The value of the Weber fraction varied inversely with contrast, differently for luminance and chromatic contrast. The results were well simulated with a simple model that accumulated change in contrast over time until a critical threshold had been reached. Two crucial aspects of the model are a second-stage temporal integration mechanism, capable of accumulating information for periods of up to 2 s, and contrast gain control, different for luminance than for chromatic stimuli. The contrast response for luminance shows very low semi-saturating contrasts and high gain, similar to LGN M-cells and cells in MT; that for colour shows high semi-saturating contrasts and low gain, similar to LGN P-cells. The results suggest that motion onset for luminance and chromatic gratings are detected by different mechanisms, probably by the magno- and parvo-cellular systems.
2001
41
1039
1048
David C. Burr; Beatrice Corsale
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/849936
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