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People vary markedly in the efficiency with which they can resolve competitive action decisions, even simple ones such as shifting gaze to one stimulus rather than another. We found that an individual's ability to rapidly resolve such competition is predicted by the concentration of GABA, the main inhibitory neurotransmitter, in a region of frontal cortex(More)
Neurophysiological and phenomenological data on sensorimotor decision making are growing so rapidly that it is now necessary and achievable to capture it in biologically inspired models, for advancing our understanding in both research and clinical settings. However, the main impediment in moving from elegant models with few free parameters to more complex(More)
Irrelevant stimulus onsets interfere with saccade planning to other stimuli, prolonging saccadic latency (the oculomotor distractor effect) or eliciting directional errors (saccadic capture). Such stimulus-driven interference has been associated with the retinotectal pathway, the direct pathway from retina to superior colliculus. Consistent with this(More)
We used an exogenous target detection cueing paradigm to examine whether intra-individual reaction time variability (IIV) or phasic alerting varied significantly between patients with amnestic mild cognitive impairment (aMCI) (n = 45) and healthy older adult controls (n = 31) or between those with aMCI who, within a 2.5 year follow-up period, developed(More)
In most visual search experiments in the laboratory, objects are presented on an isolated, blank background. In most real world search tasks, however, the background is continuous and can be complex. In six experiments, we examine the ability of the visual system to separate search items from a background. The results support a view in which objects are(More)
Sensory information travels to visual and motor areas via several distinct pathways, some of them being fast-like the achromatic magnocellular and retinotectal routes-and others slower-those carrying chromatic signals, in particular S-opponent signals. It is debated whether common visual processing stages are used for different types of responses, such as(More)
Monocular viewing conditions show an asymmetry between stimuli presented in the temporal and nasal visual fields in their efficiency for automatically triggering eye saccades and grasping attention. For instance, observers free to make a saccade to one of two stimuli presented together orient preferentially to the temporal stimulus. Such naso-temporal(More)
The spatiochromatic properties of the red-green dimension of human colour vision appear to be optimized for picking fruit in leaves at about arms' reach. However, other evidence suggests that the task of spotting fruit from a distance might be more important. This discrepancy may arise because the task a system (e.g. human trichromacy) is best at is not(More)