Abstract
Background: Transient attention enhances contrast sensitivity by increasing the gain of the neurons processing a stimulus. Conversely, adaptation reduces contrast sensitivity by reducing neuronal gain. Given that both attention and adaptation act on the gain of the neurons processing the relevant stimuli, their effect may interact. We hypothesize that transient attention would reduce the effect of adaptation on contrast sensitivity.
Method: We presented two 4 cpd Gabor patches for 100 ms at 5 deg of eccentricity to the left and right of a central fixation point. On each trial one Gabor was slightly tilted (target) and the other was vertical, and contrast was manipulated to obtain psychometric functions. Observers performed a left/right orientation-discrimination task on the target. There were two attentional conditions: neutral and peripheral. The cue was a small bar presented for 40 ms before (60 ms ISI) the stimulus display either at fixation (neutral) or above the target (peripheral). There were two adaptation conditions: adapt-same and adapt-different orientation. Before each 20-trial block, observers adapted for 60 s to two 4-cpd counter-phase flickering (7.5 Hz) Gabor patches (5 deg eccentricity). Top-up stimuli were presented for 2.5s before each test trial. The adapting stimuli were vertical in the adapt-same condition and horizontal in the adapt-different condition.
Results: Performance in neutral trials was better in the adapt-different than in the adapt-same condition (adaptation effect). Performance in peripheral trial was better than in neutral trials (attention effect). Moreover, these effects interacted: performance in peripheral trials was comparable for the adapt-different and adapt-same conditions. These results indicate that transient attention diminishes the effect of adaptation.
NSF - BCF-9910734 & The Beatrice and Samuel A. Seaver Foundation