Target frequency influences antisaccade endpoint bias: Evidence for perceptual averaging

Abstract

Perceptual judgments related to stimulus-sets are represented computationally different than individual items. In particular, the perceptual averaging hypothesis contends that the visual system represents target properties (e.g., eccentricity) via a statistical summary of the individual targets included within a stimulus-set. Here we sought to determine whether perceptual averaging governs the visual information mediating an oculomotor task requiring top-down control (i.e., antisaccade). To that end, participants completed antisaccades (i.e., saccade mirror-symmetrical to a target) – and complementary prosaccades (i.e., saccade to veridical target location) – to different target eccentricities (10.5°, 15.5° and 20.5°) located left and right of a common fixation. Importantly, trials were completed in blocks wherein eccentricities were presented with equal frequency (i.e., control condition) and when the ‘proximal’ (10.5°: i.e., proximal-weighting condition) and ‘distal’ (20.5°: i.e., distal-weighting condition) targets were respectively presented five times as often as the other eccentricities. If antisaccades are governed by a statistical summary then amplitudes should be biased in the direction of the most frequently presented target within a block. As expected, pro- and antisaccade across each target eccentricity were associated with an undershooting bias and prosaccades were refractory to the manipulation of target frequency. Most notably, antisaccades in the proximal-weighting condition had a larger undershooting bias than the control condition, whereas the converse was true for the distal-weighing condition; that is, antisaccades were biased in the direction of the most frequently presented target. Thus, we propose that perceptual averaging extends to motor tasks requiring top-down cognitive control.

The antisaccade task: Vector inversion contributes to a statistical summary representation of target eccentricities

“…Notably, however, our group's (Gillen, Weiler, & Heath, 2013) quantitative analysis of Kapoula's data showed that her results provide no evidence for a range effect, and our work provided further evidence to support the overwhelming contention that prosaccades produce an invariant undershooting bias (Becker, 1989;Harris, 1995). What is more, the range effect is entirely incompatible with our group's previous work showing that antisaccades do not overshoot veridical target eccentricity regardless of the range and magnitude of target eccentricities included within a stimulus set (Gillen & Heath, 2014a;2014b).…”

“…Instead, results support the contention that undershooting is an invariant control strategy designed to minimize energy expenditure (Becker, 1989) and/or saccade flight time (Harris, 1995;Gillen et al, 2013). Additionally, amplitudes were refractory to the different target-weighting conditions (see also Gillen & Heath, 2014b) and is a result demonstrating that absolute and retinotopically organized visual information mediates prosaccade sensorimotor transformations (Wurtz & Albano, 1980). In other words, the absolute visual information supporting prosaccades is incompatible with a SSR.…”

“…One framework to address this issue is to investigate whether a target property (e.g., eccentricity) representing the SSR of a stimulus-set facilitates the latency and/ or amplitude of goal-directed saccades. In one examination of this issue, work by our group (Gillen & Heath, 2014b; see also Gillen & Heath, 2014a) had participants complete prosaccades (i.e., saccade to veridical target location) and antisaccades (i.e., saccade to the target's mirror symmetrical location) to briefly presented targets (i.e., 50 ms) located 10.58 (''proximal'' target), 15.58 (''middle'' target), and 20.58 (''distal'' target) left and right of a common fixation. Importantly, pro-and antisaccades were completed across conditions that differed with regard to the weighting of target eccentricity frequency.…”

“…An issue that remains to be addressed is whether response suppression and the introduction of a memory delay or vector inversion contributes to the mediation of saccade endpoints via a SSR. To that end, we had participants complete pro-and antisaccades cued by a briefly presented target (i.e., 50 ms; eccentricities of 10.58, 15.58, and 20.58) across distal-, control-, and proximal-weighting conditions (i.e., the same task and weighting conditions as employed by Gillen & Heath, 2014b). In addition, target-weighting conditions were performed in a delay prosaccade task wherein a 2000ms interval was introduced between target extinction and movement onset.…”

Oculomotor Executive Dysfunction during the Early and Later Stages of Sport-Related Concussion Recovery

“…antisaccades require the activation of an extensive frontoparietal network involved in the timeconsuming executive processes of response suppression and vector inversion (Munoz & Everling, 2004). Moreover, the smaller antisaccade gains (i.e., less accurate endpoints) indicate that decoupling the spatial relations between stimulus and response renders motor output that is supported via visual information that is functionally distinct (i.e., relative) from the direct (i.e., absolute) visual information mediating prosaccades (Gillen & Heath, 2014a;2014b;Heath, Gillen, & Weiler, 2015). These behavioural findings therefore provide a framework for examining executive and non-executive oculomotor dysfunction during the acute and later stages of concussion recovery.…”