Competition of salience and informational value in saccadic adaptation

Humans maintain saccade accuracy through an adaptive learning mechanism, called saccadic adaptation. Classically, this mechanism is studied using a single perceptually irrelevant target. Recent work demonstrated that saccadic adaptation does also occur in response to a perceptual task (Schütz, Kerzel, & Souto, 2014) and in paradigms with multiple stimuli (Madelain, Harwood, Herman, & Wallman, 2010). Furthermore, adaptation to a non-salient target can be disturbed by a salient distractor (Khan, McFadden, Harwood, & Wallman, 2014). Here, we test the hypothesis that saccadic adaptation is not only influenced by stimulus saliency, but also by the informational value of two competing task-relevant targets. Our participants had to judge the orientation of two Gabor patches. At trial beginning, both patches were overlaid and appeared at a horizontal eccentricity of 12.5°. During the saccade, they were vertically displaced by ± 2° in opposite directions. The salient Gabor had low spatial-frequency and high contrast, such that it was highly visible in the periphery. The informative Gabor had high spatial-frequency and low contrast, such that it was poorly visible in the periphery and therefore yielding high information gain by a saccade. We found that with a perceptual task, in which participants had to report their judgments on both Gabors sequentially, saccadic adaptation was directed towards the Gabor they had to report on first. Here, the adaptation profiles differed between the salient and the informative Gabor. With a perceptual task, in which both stimuli were reported simultaneously, however, saccadic adaptation was directed towards the informative Gabor, albeit with a small gain. These findings demonstrate that saccadic adaptation can occur even when there is competition between several task-relevant targets after the saccade. Direction and magnitude of adaptation can be determined by the targets’ relative informative value or by temporal priority imposed by task demands.