Abstract
Attention can be directed to particular spatial locations, or to objects that appear at anticipated points in time. While most work has focused on spatial or temporal attention in isolation, we investigated covert tracking of smoothly moving objects, which requires continuous coordination of both. We tested two propositions about the neural and cognitive basis of this operation: first that covert tracking is a right hemisphere function, and second that pre-motor components of the oculomotor system are responsible for driving covert spatial attention during tracking. We simultaneously recorded event related potentials (ERPs) and eye position while participants covertly tracked dots that moved leftward or rightward at 12 or 20°/s. ERPs were sensitive to the direction of target motion. Topographic development in the leftward motion was a mirror image of the rightward motion, suggesting that both hemispheres contribute equally to covert tracking. Small shifts in eye position were also lateralized according to the direction of target motion, implying covert activation of the oculomotor system. The data addresses two outstanding questions about the nature of visuospatial tracking. First, covert tracking is reliant upon a symmetrical frontoparietal attentional system, rather than being right lateralized. Second, this same system controls both pursuit eye movements and covert tracking.
Highlights
Selective attention enhances sensory inputs that are relevant to current goals, and inhibits task-irrelevant inputs
We found that Event Related Potentials (ERPs) related to the direction of target motion were symmetrical; that is, the contribution of each hemisphere depends on the horizontal direction of target motion
We found small shifts in eye position lateralized according to the direction of target motion, implying covert activation of the oculomotor system
Summary
Selective attention enhances sensory inputs that are relevant to current goals, and inhibits task-irrelevant inputs. A great deal of research has been carried out into how people can shift their attention to spatial locations covertly, that is, without moving their eyes [1]. Researchers have considered attention to stimuli that appear at an expected point in time: Doherty et al [3] presented a single dot target that moved rightwards in a series of discrete steps, before disappearing behind an occluder. ERPs were recorded at the point when the target reappeared after occlusion. The P1 component was largest when the target reappeared at the expected time and expected location, demonstrating that selective attention can operate in both the spatial and temporal domains [4]
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