Lawrence M. Ward

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OBJECTIVE To review the stochastic resonance phenomena observed in sensory systems and to describe how a random process ('noise') added to a subthreshold stimulus can enhance sensory information processing and perception. RESULTS Nonlinear systems need a threshold, subthreshold information bearing stimulus and 'noise' for stochastic resonance phenomena to(More)
Explaining the emergence of a coherent conscious percept and an intentional agent from the activity of distributed neurons is key to understanding how the brain produces higher cognitive processes. Gamma-band synchronization has been proposed to be a mechanism for the functional integration of neural populations that together form a transitory, large-scale,(More)
This article deals with the problem of how attention is distributed to different levels of detail (global, local) in visual scenes. Six experiments explore the effect of a previous level of processing on current processing. The contention that processing at a given level of detail biases the distribution of attention so that more is allocated to that level(More)
It is well known that sensory events of one modality can influence judgments of sensory events in other modalities. For example, people respond more quickly to a target appearing at the location of a previous cue than to a target appearing at another location, even when the two stimuli are from different modalities. Such cross-modal interactions suggest(More)
Although typically assumed to degrade performance, random fluctuations, or noise, can sometimes improve information processing in non-linear systems. One such form of 'stochastic facilitation', stochastic resonance, has been observed to enhance processing both in theoretical models of neural systems and in experimental neuroscience. However, the two(More)
When attention is allocated to one visual hemifield, increased alpha power is observed in ipsilateral visual cortex. This has been attributed to synchronization of alpha-band oscillations within cortical regions which reflects inhibitory processing. Recent results, however, indicate that synchronization of alpha oscillations between cortical regions is(More)
Two experiments are described in which visual and/or auditory location precues preceded visual or auditory targets. Observers were required to judge the location of the targets. Conditions were such that involuntary, stimulus-driven attention shifts were the only ones likely to occur and give rise to cueing effects. It was found that visual precues affected(More)
Event-related brain potentials (ERPs) were recorded during two spatial-cuing experiments using nonpredictive cues. Our primary goal was to determine the electrophysiological consequences of inhibition of return (IOR). At long (> 500 msec) cue-target intervals, subjects responded more slowly to targets that appeared at or near the cued location, relative to(More)
Consciousness has been proposed to emerge from functionally integrated large-scale ensembles of gamma-synchronous neural populations that form and dissolve at a frequency in the theta band. We propose that discrete moments of perceptual experience are implemented by transient gamma-band synchronization of relevant cortical regions, and that disintegration(More)