Stephen L. Macknik

Learn More
NATURE REVIEWS | NEUROSCIENCE VOLUME 5 | MARCH 2004 | 229 We live in a constantly changing world, so nervous systems have evolved to detect changes in our environment. Motion in our visual field might indicate that a predator is approaching or that prey is escaping. Stationary objects generally pose less of a threat and so tend to be studiously ignored(More)
A brief visual target stimulus may be rendered invisible if it is immediately preceded or followed by another stimulus. This class of illusions, known as visual masking, may allow insights into the neural mechanisms that underlie visual perception. We have therefore explored the temporal characteristics of masking illusions in humans, and compared them with(More)
When viewing a stationary object, we unconsciously make small, involuntary eye movements or 'microsaccades'. If displacements of the retinal image are prevented, the image quickly fades from perception. To understand how microsaccades sustain perception, we studied their relationship to the firing of cells in primary visual cortex (V1). We tracked eye(More)
Our eyes move continually, even while we fixate our gaze on an object. If fixational eye movements are counteracted, our perception of stationary objects fades completely, due to neural adaptation. Some studies have suggested that fixational microsaccades refresh retinal images, thereby preventing adaptation and fading. However, other studies disagree, and(More)
When images are stabilized on the retina, visual perception fades. During voluntary visual fixation, however, constantly occurring small eye movements, including microsaccades, prevent this fading. We previously showed that microsaccades generated bursty firing in the primary visual cortex (area V-1) in the presence of stationary stimuli. Here we examine(More)
Microsaccades are known to occur during prolonged visual fixation, but it is a matter of controversy whether they also happen during free-viewing. Here we set out to determine: 1) whether microsaccades occur during free visual exploration and visual search, 2) whether microsaccade dynamics vary as a function of visual stimulation and viewing task, and 3)(More)
Spatial attention enhances our ability to detect stimuli at restricted regions of the visual field. This enhancement is thought to depend on the difficulty of the task being performed, but the underlying neuronal mechanisms for this dependency remain largely unknown. We found that task difficulty modulates neuronal firing rate at the earliest stages of(More)
Microsaccades are the largest and fastest of the fixational eye movements, which are involuntary eye movements produced during attempted visual fixation. In recent years, the interaction between microsaccades, perception and cognition has become one of the most rapidly growing areas of study in visual neuroscience. The neurophysiological consequences of(More)
In visual masking, visible targets are rendered invisible by modifying the context in which they are presented, but not by modifying the targets themselves. Here I summarize a decade of experimentation using visual masking illusions in which my colleagues and I have begun to establish the minimal set of conditions necessary to maintain the awareness of the(More)
When we attempt to fix our gaze, our eyes nevertheless produce so-called 'fixational eye movements', which include microsaccades, drift and tremor. Fixational eye movements thwart neural adaptation to unchanging stimuli and thus prevent and reverse perceptual fading during fixation. Over the past 10 years, microsaccade research has become one of the most(More)