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

Antisaccades require the top-down suppression of a stimulus-driven prosaccade (i.e., response suppression) and the inversion of a target's spatial location to mirror-symmetrical space (i.e., vector inversion). Moreover, recent work has shown that antisaccade amplitudes are characterized by a statistical summary representation (SSR) of the target eccentricities included in a stimulus-set--a result suggesting that antisaccades are supported via the same relative visual information as perceptions. The present investigation sought to determine whether response suppression and the disruption of real-time control or vector inversion contribute to a SSR in oculomotor control. Participants completed pro- and antisaccades (target eccentricities of 10.5°, 15.5°, and 20.5°) in blocks of trials that differed with regard to the frequency that individual target eccentricities were presented. The manipulation of target eccentricity frequency was used to determine whether the most frequently presented target within a stimulus-set (i.e., the SSR) influences saccade amplitudes. Moreover, we disrupted the real-time control of prosaccades by requiring participants to suppress their response for a brief visual delay (i.e., 2000 ms: so-called delay prosaccade). As expected, antisaccades and delay prosaccades produced equivalent reaction times. In turn, amplitudes for delay prosaccades were refractory to the manipulation of target eccentricity frequency, whereas antisaccades were biased in the direction of the most frequently presented target within a stimulus-set. Accordingly, we propose that vector inversion contributes to the mediation of target eccentricities via a SSR and that such a phenomenon provides convergent evidence that a relative visual percept mediates antisaccades.