Ocular dominance is the tendency to prefer visual input from one eye to the other [e.g. Porac, C. & Coren, S. (1976). The dominant eye. Psychological Bulletin 83(5), 880-897]. In standard sighting tests, most people consistently fall into either the left- or right eye-dominant category [Miles, W. R. (1930). Ocular dominance in human adults. Journal of General Psychology 3, 412-420]. Here we show this static concept to be flawed, being based on the limited results of sighting with gaze pointed straight ahead. In a reach-grasp task for targets within the binocular visual field, subjects switched between left and right eye dominance depending on horizontal gaze angle. On average, ocular dominance switched at gaze angles of only 15.5 degrees off center.
Optic ataxia is a disorder associated with posterior parietal lobe lesions, in which visually guided reaching errors typically occur for peripheral targets. It has been assumed that these errors are related to a faulty sensorimotor transformation of inputs from the 'ataxic visual field'. However, we show here that the errors observed in the contralesional field in optic ataxia depend on a dynamic gaze-centered internal representation of reach space.
When moving through our environment, it is vital to preferentially process positions on our future path in order to react quickly to critical situations. During smooth pursuit, attention may be directed ahead with either a focused locus or a broad bias. We examined the 2D spatial extent of attention during a smooth pursuit task using both saccade (SRT) and manual (MRT) reaction times as measures of attentional allocation. Targets were flashed at various locations around current eye position while subjects pursued a moving target. Subjects made a saccade or pressed a button as soon as they perceived the target. Both SRTs and MRTs were shortest to targets flashed ahead of compared to behind the direction of pursuit across half of the visual field ahead of pursuit direction. Furthermore, we found an increase specific to SRTs at small target eccentricities directly ahead of pursuit, which may be related to an additional saccade trigger strategy; small saccades take longer to execute if smooth pursuit brings the eyes close to the target. In summary, both SRTs and MRTs revealed that attention is by default broadly allocated in the visual hemi-field ahead of the line of sight during smooth pursuit eye movements. This attentional bias may serve a predictive purpose for facilitating the processing of upcoming events.
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