Macknik Lab

The mammalian visual system includes numerous brain areas that are profusely interconnected. With few exceptions, these connections are reciprocal. Anatomical feedback connections in general outnumber feedforward connections, leading to widespread speculation that feedback connections play a critical role in visual awareness. However, evidence from physiological experiments suggests that feedback plays a modulatory role, rather than a driving role. Here we discuss theoretical constraints on the significance of feedback’s anatomical numerical advantage, and we describe theoretical limits on feedback’s potential physiological impact. These restrictions confine the potential role of feedback in visual awareness and rule out some extant models of visual awareness that require a fundamental role of feedback. We propose that the central role of feedback is to maintain visuospatial attention, rather than visual awareness. Our conclusions highlight the critical need for experiments and models of visual awareness that control for the effects of attention. As a matter of clarity in this chapter: by “visual awareness” or “visibility” we mean the conscious perception that a stimulus is visible. Thus, for the purposes of this discussion, we use the terms visual awareness, visibility, and consciousness interchangeably.

Visual illusions are subjective percepts that do not match the physical reality of the world. When we experience a visual illusion, we may see something that is not there, fail to see something that is there, or see something different from what is there. Visual illusions not only demonstrate the ways in which the brain fails to recreate the physical world, but they are also useful tools to identify the neural circuits and computations by which the brain constructs our visual experience.

Nineteenth-century visual scientists such as Michel-Eugène Chevreul, Ernst Mach, Hermann von Helmholtz, Ewald Hering, and Johannes Peter Müller discovered that simultaneously presented stimuli could affect each other’s perceived contrast. For example, notice how each of the solid stripes in the figure appears lighter on the left than on the right, even though each stripe has the same physical intensity across its width. This illusion is called “Mach bands,” and it illustrates how the contrast of a stimulus is enhanced at its borders. This entry describes spatial and temporal contrast enhancement at borders.

Lateral inhibition, is a decrease in response in neurons that occurs when neighboring neurons become activated. Activity in any one of the excitatory neurons can inhibit its neighbors indirectly by activating the inhibitory neurons that then inhibit their neighbors. When a stimulus (such as a bar of light or any other stimulus) excites a number of neurons in the network, the effect of inhibition is to suppress the neurons just outside the edge of the bar because those neurons are inhibited but not excited. Further, because the neurons just inside the edges of the bar are excited by light and only inhibited by one neighbor, they are especially active. This leads to perceptual contrast enhancement at borders. Further research showed that lateral inhibition also applied to overlapping stimuli, and that its strength fell off with distance between the interacting stimuli.

Lateral inhibition, is a decrease in response in neurons that occurs when neighboring neurons become activated. Activity in any one of the excitatory neurons can inhibit its neighbors indirectly by activating the inhibitory neurons that then inhibit their neighbors. When a stimulus (such as a bar of light or any other stimulus) excites a number of neurons in the network, the effect of inhibition is to suppress the neurons just outside the edge of the bar because those neurons are inhibited but not excited. Further, because the neurons just inside the edges of the bar are excited by light and only inhibited by one neighbor, they are especially active. This leads to perceptual contrast enhancement at borders. Further research showed that lateral inhibition also applied to overlapping stimuli, and that its strength fell off with distance between the interacting stimuli.

Perception is modified by changes in visual stimuli that take place over time. For example, the apparent brightness of a stimulus may vary as a function of duration, even if its luminance is constant. Further, the appearance of a stimulus is affected by its timing with respect to other stimuli. For example, a flash of light may not appear to be a flash at all if it is embedded in a series of flashes (a phenomenon called flicker fusion, described further in the entry). Also described in this entry are the roles of temporal factors in brightness perception and factors in visual physiology and stimulus visibility.

In visual masking, a visual stimulus called the “target” becomes less visible due to interactions with other stimuli, called “masks.” The 19th century scientist S. Exner first discovered masking in the visual system. The birth of visual masking was an artifact in one of Exner’s studies of consciousness. He had been trying to determine the shortest flash duration necessary for a bar of light to be visible. As a control condition, he presented two identical bars in different places of the visual field and at different times, expecting that they would be perceived as identical in appearance. Exner was surprised to find that this was not, in fact, so. Under certain specific timing conditions, the first bar was rendered invisible by the presentation of the second bar.

Our brains are exquisitely tuned to perceive, recognize and remember faces. We can easily find a friend’s face among dozens or hundreds of unfamiliar faces in a busy street. We look at each other’s facial expressions for signs of appreciation and disapproval, love and contempt. We carefully select the images to go with our Facebook profiles. And even after we have corresponded or spoken on the phone with somebody for a long time, we are often relieved when we meet him or her in person and are able to put “a face to the name.”

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 microsaccades have been the focus of less attention, however, as have the oculomotor mechanisms that generate and control microsaccades. Here we review the latest neurophysiological findings concerning microsaccades and discuss their relationships to perception and cognition. We also point out the current gaps in our understanding of the neurobiology of microsaccades and identify the most promising lines of enquiry.

Neurons in primary visual cortex (V1) are frequently classified based on their response linearity: the extent to which their visual responses to drifting gratings resemble a linear replica of the stimulus. This classification is supported by the finding that response linearity is bimodally distributed across neurons in area V1 of anesthetized animals. However, recent studies suggest that such bimodal distribution may not reflect two neuronal types but a nonlinear relationship between the membrane potential and the spike output. A main limitation of these previous studies is that they measured response linearity in anesthetized animals, where the distance between the neuronal membrane potential and the spike threshold is artificially increased by anesthesia. Here, we measured V1 response linearity in the awake brain and its correlation with the neuronal spontaneous firing rate, which is related to the distance between membrane potential and threshold. Our results demonstrate that response linearity is bimodally distributed in awake V1 but that it is poorly correlated with spontaneous firing rate. In contrast, the spontaneous firing rate is best correlated to the response selectivity and response latency to stimuli.

When corners are embedded in a luminance gradient, their perceived salience varies linearly with corner angle. Here we hypothesize that this relationship may hold true for all corners, not just corner gradients. To test this hypothesis, we developed a novel variant of the flicker-augmented contrast illusion that employs solid (non-gradient) corners of varying angles to modify perceived brightness. We flickered solid corners from dark to light grey (50% luminance over time) against a black or a white background. With this new stimulus, subjects compared the apparent brightness of corners, which did not vary in actual luminance, to non-illusory stimuli that varied in actual luminance. We found that the apparent brightness of corners was linearly related to the sharpness of corner angle. Thus this relationship is not solely an effect of corners embedded in gradients, but may be a general principle of corner perception. These findings may have important repercussions for brain mechanisms underlying the early visual processing of shape and brightness. A large fraction of Vasarely's art showcases the perceptual salience of corners, curvature and terminators. Several of these artworks and their implications for visual processing are discussed.

Alas! Poor Yorick. I knew him well. A fellow of infinite jest, of most excellent fancy; he hath borne me on his back a thousand times; and now, how abhorred in my afterimage he is! Well... that's what Hamlet would have said, had he been holding the vintage Pear's Soap advertisement bearing Yorick's skull in the accompanying slide, rather than a dug up and rotting Danish cranium.

It's Valentine's season, which means that everywhere you look there are heart-shaped balloons, pink greeting cards and candy boxes filled with chocolate. But what is true love? Does it exist? Or is it simply a cognitive illusion, a trick of the mind? Let us count the ways. Contrary to the anatomy referenced in all of our favorite love songs, love (as with every other emotion we feel) is not rooted in the heart, but in the brain. (Unfortunately, Hallmark has no plans to mass-produce chocolate-covered arrow-pierced brains in the near future.) By better understanding how the brain falls in love, we can learn about why the brain can get so obsessed with this powerful emotion. In fact, some scientists even see love as a sort of addiction.

We recently proposed, in collaboration with five professional magicians, that neuroscientists and magicians should join forces in the study of human perception and cognition. Our two-pronged approach was that, first, magic techniques could be used as powerful tools in cognitive neuroscience research, and that, second, the perception of magic tricks will be best understood from a neurobiological perspective. While commending our Perspective, Lamont and Henderson point out that scientific interest in magic is not new, and that previous attempts to establish a theory of magic have failed. They also mention that Lamont and Wiseman's classification of conjuring effects -- adopted in our Perspective -- did not merely list the main categories, but also indicated the methods behind the tricks. Finally, they refer to Simons and Chabris's classic study of inattentional blindness, and propose that observers that look directly at the gorilla will not fail to notice it.

Consciousness is the feeling of life's experience. It is a difficult concept to define precisely, however, because the word "consciousness" means different things in different contexts. For instance, one may say that we are unconscious during sleep, despite the fact that, while asleep, we sometimes experience powerful and highly salient dreams (these dreams fit the definition of consciousness as stated in the first sentence above). Does this mean that it is possible to be conscious of our unconscious experiences (an obvious semantic contradiction)? Or does this mean that dreams during sleep are not really unconscious? Because of these and many other semantic difficulties, the theorist Francis Crick (who also described the structure of DNA with James Watson), and his collaborator Christof Koch, suggested that we set aside the semantics and avoid defining the term consciousness linguistically. Instead, we should strive to establish the neural correlates of experience, or the neural correlates of consciousness (NCC). By determining the NCC, we will eventually arrive at a neurophysiological definition of consciousness.

In an impossible figure, seemingly real objects -- or parts of objects -- form geometrical relations that physically cannot happen. The artist M.C. Escher, for instance, depicted reversible staircases and perpetually flowing streams, whereas mathematical physicist Roger Penrose drew his famously impossible triangle and visual scientist Dejan Todorovic created an Elusive Arch that won him Third Prize of the 2005 Best Visual Illusion of the Year Contest. These effects challenge our hard-earned perception that the world around us follows certain, inviolable rules. They also reveal that our brains construct the feeling of a global percept, --or individual item we perceive,-- by sewing together multiple local percepts. As long as the local relation between surfaces and objects follow the rules of nature, our brains don't seem to mind that the global percept is impossible.

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) whether saccades and microsaccades share characteristics that might argue in favor of a common saccade-microsaccade oculomotor generator. Human subjects viewed naturalistic stimuli while performing various viewing tasks, including visual exploration, visual search, and prolonged visual fixation. Their eye movements were simultaneously recorded with high precision. Our results show that microsaccades are produced during the fixation periods that occur during visual exploration and visual search. Microsaccade dynamics during free-viewing moreover varied as a function of visual stimulation and viewing task, with increasingly demanding tasks resulting in increased microsaccade production. Moreover, saccades and microsaccades had comparable spatiotemporal characteristics, including the presence of equivalent refractory periods between all pair-wise combinations of saccades and microsaccades. Thus our results indicate a microsaccade–saccade continuum and support the hypothesis of a common oculomotor generator for saccades and microsaccades.

During visual fixation, human eyes are never still. Instead, they constantly produce involuntary "fixational eye movements." Fixational eye movements overcome neural adaptation and prevent visual fading: thus they are an important tool to understand how the brain makes the environment visible. The last decade has seen a growing interest in the analysis of fixational eye movements in humans and primates, as well as in their perceptual and physiological consequences. However, no comprehensive comparison of fixational eye movements across species has been offered. Here we review five decades of fixational eye movement studies in non-human vertebrates, and we discuss the existing evidence concerning their physiological and perceptual effects. We also provide a table that summarizes the physical parameters of the different types of fixational eye movements described in non-human vertebrates.

Scientists did not invent the vast majority of visual illusions. Rather, they are the work of visual artists, who have used their insights into the workings of the visual system to create visual illusions in their pieces of art. We have previously pointed out in our essays that, long before visual science existed as a formal discipline, artists had devised techniques to "trick" the brain into thinking that a flat canvas was three-dimensional, or that a series of brushstrokes in a still life was in fact a bowl of luscious fruit. Thus the visual arts have sometimes preceded the visual sciences in the discovery of fundamental vision principles, through the application of methodical -- although perhaps more intuitive -- research techniques. In this sense, art, illusions and visual science have always been implicitly linked.

Neuroscience is becoming familiar with the methods of magic by subjecting magic itself to scientific study --in some cases showing for the first time how some of its methods work in the brain. Many studies of magic conducted so far confirm what is known about cognition and attention from earlier work in experimental psychology. A cynic might dismiss such efforts: Why do yet another study that simply confirms what is already well known? But such criticism misses the importance and purpose of the studies. By investigating the techniques of magic, neuroscientists can familiarize themselves with methods that they can adapt to their own purposes. Indeed, we believe that cognitive neuroscience could have advanced faster had investigators probed magicians' intuitions earlier. Even today magicians may have a few tricks up their sleeves that neuroscientists have not yet adopted.

Artificial scotomas positioned within peripheral dynamic noise fade perceptually during visual fixation (that is, the surrounding dynamic noise appears to fill-in the scotoma). Because the scotomas' edges are continuously refreshed by the dynamic noise background, this filling-in effect cannot be explained by low-level adaptation mechanisms (such as those that may underlie classical Troxler fading). We recently showed that microsaccades counteract Troxler fading and drive first-order visibility during fixation. Here we set out to determine whether microsaccades may counteract the perceptual filling-in of artificial scotomas and thus drive second-order visibility. If so, microsaccades may not only counteract low-level adaptation but also play a role in higher perceptual processes. We asked subjects to indicate, via button press/release, whether an artificial scotoma presented on a dynamic noise background was visible or invisible at any given time. The subjects' eye movements were simultaneously measured with a high precision video system. We found that increases in microsaccade production counteracted the perception of filling-in, driving the visibility of the artificial scotoma. Conversely, decreased microsaccades allowed perceptual filling-in to take place. Our results show that microsaccades do not solely overcome low-level adaptation mechanisms but they also contribute to maintaining second-order visibility during fixation.

Just as vision scientists study visual art and illusions to elucidate the workings of the visual system, so too can cognitive scientists study cognitive illusions to elucidate the underpinnings of cognition. Magic shows are a manifestation of accomplished magic performers' deep intuition for and understanding of human attention and awareness. By studying magicians and their techniques, neuroscientists can learn powerful methods to manipulate attention and awareness in the laboratory. Such methods could be exploited to directly study the behavioural and neural basis of consciousness itself, for instance through the use of brain imaging and other neural recording techniques.

The photoreceptors of your retina are like the CCD chip in your camera: just a matrix of light detectors. They individually respond to changes in light level, whether those changes are due to actual motion or to stationary changes in brightness. Then specialized motion-detection neurons of the brain analyze the responses from populations of photoreceptors to infer motion. So although Ben Franklin may have admonished that productive activity (action) is better than unproductive activity (motion), he was also correct in the neurobiological sense: the perception of motion need not arise from a veridical action in the world

Just as the painter creates the illusion of depth on a flat canvas, our brain creates the illusion of depth based on information arriving from our essentially 2-D retinas. Visual illusions show us that color, brightness and shape are not absolute terms but are subjective, relative experiences actively created by complicated brain circuits. This is true not only of visual experiences but of any sensation. Whether we experience the feeling of "redness," the appearance of squareness, or emotions such as love and hate, these are the results of the electrical activity of neurons in our brain.

Visual images consisting of repetitive patterns can elicit striking illusory motion percepts. For almost 200 years, artists, psychologists, and neuroscientists have debated whether this type of illusion originates in the eye or in the brain. For more than a decade, the controversy has centered on the powerful illusory motion perceived in the painting Enigma, created by op-artist Isia Leviant. However, no previous study has directly correlated the Enigma illusion to any specific physiological mechanism, and so the debate rages on. Here, we show that microsaccades, a type of miniature eye movement produced during visual fixation, can drive illusory motion in Enigma. We asked subjects to indicate when illusory motion sped up or slowed down during the observation of Enigma while we simultaneously recorded their eye movements with high precision. Before "faster" motion periods, the rate of microsaccades increased. Before "slower/no motion" periods, the rate of microsaccades decreased. These results reveal a direct link between microsaccade production and the perception of illusory motion in Enigma and rule out the hypothesis that the origin of the illusion is purely cortical.

The eyes are the windows to the soul. This fact is why we ask people to look us in the eye and tell us the truth. Or why we get worried when someone gives us the evil eye or has a wandering eye. Our everyday language is full of expressions that refer to where people around us are looking. Particularly if they happen to be looking in our direction.

When corners are embedded in a luminance gradient, their perceived salience varies linearly with corner angle (Troncoso et al., 2005). Here we hypothesize that this relationship may hold true for all corners, not just corner gradients. To test this hypothesis, we developed a novel variant of the flicker-augmented contrast illusion that employs solid (non-gradient) corners of varying angles to modify perceived brightness. We flickered solid corners from dark to light grey (50% luminance over time) against a black or a white background. With this new stimulus, subjects compared the apparent brightness of corners, which did not vary in actual luminance, to non-illusory stimuli that varied in actual luminance. We found that the apparent brightness of corners was linearly related to the sharpness of corner angle. Thus this relationship is not solely an effect of corners embedded in gradients, but may be a general principle of corner perception. These findings may have important repercussions for brain mechanisms underlying the early visual processing of shape and brightness. A large fraction of Vasarely's art showcases the perceptual salience of corners, curvature and terminators. Several of these artworks and their implications for visual processing are discussed.

How could we have missed it? Hundreds, perhaps thousands, of visual scientists, psychologists, neuroscientists, visual artists, architects, engineers and biologists all missed it -- until now. The "it" in question is the Leaning Tower Illusion, discovered by Frederick Kingdom, Ali Yoonessi, and Elena Gheorghiu of McGill University. In this illusion, two identical side-by-side images of the same tilted and receding object appear to be leaning at two different angles. This incredible effect was first noticed just last year in images of the famed Leaning Tower of Pisa, but it also works with paired images of other tilted objects.

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 cortical visual processing (area V1) in monkey (Macaca mulatta). These modulations were spatially specific: increasing task difficulty enhanced V1 neuronal firing rate at the focus of attention and suppressed it in regions surrounding the focus. Moreover, we found that response enhancement and suppression are mediated by distinct populations of neurons that differ in direction selectivity, spike width, interspike-interval distribution and contrast sensitivity. Our results provide strong support for center-surround models of spatial attention and suggest that task difficulty modulates the activity of specific populations of neurons in the primary visual cortex.

It's a fact of neuroscience that everything we experience is actually a figment of our imagination. Although our sensations feel accurate and truthful, they do not necessarily reproduce the physical reality of the outside world. Of course, many experiences in daily life reflect the physical stimuli that enter the brain. But the same neural machinery that interprets actual sensory inputs is also responsible for our dreams, delusions and failings of memory. In other words, the real and the imagined share a physical source in the brain. So take a lesson from Socrates: "All I know is that I know nothing."

The visual arts sometimes precede the visual sciences in the discovery of fundamental vision principles. Victor Vasarely's "Nested Squares" paintings show an illusory effect in which corners look brighter and more salient than straight edges, despite having equivalent luminance. Here we summarize some of our recent experiments, originally based on Victor Vasarely's "Nested Squares" illusion, to discover the underlying perceptual and physiology principles. The results have given us significant insight into how corners, angles, curves and terminating line endings affect the appearance of shape and brightness in our brains.

The source of many of the world's woes might be tracked to a specific brain area responsible for identifying people that are not of our ilk. If so, a study on the neural bases of prejudice and its modulation (read abstract or download the pdf), by Jason Mitchell and Mahzarin R. Banaji, of Harvard University, and C Neil Macrae, at the University of Aberdeen in Scotland, published in Neuron in May 2006, could be as important to the burgeoning field of social cognitive neuroscience as Martin Luther King Jr.'s "I have a dream" speech was to the American civil rights movement.

This paper reviews the potential role of feedback in visual masking, for and against. Our analysis reveals constraints for feedback mechanisms that limit their potential role in visual masking, and in other general brain functions. We propose a feedforward model of visual masking, and provide a hypothesis to explain the role of feedback in visual masking and visual processing in general. We review the anatomy and physiology of feedback mechanisms, and propose that the massive ratio of feedback versus feedforward connections in the visual system may be explained solely by the critical need for top-down attentional modulation. We discuss the merits of visual masking as a tool to discover neural correlates of consciousness, especially as compared to other popular illusions, such as binocular rivalry. Finally, we propose a new set of neurophysiological standards needed to establish whether any given neuron or brain circuit may be the neural substrate of awareness.

When the eyes fix on something, they still jump imperceptibly in ways that turn out to be essential for seeing. For decades, scientists have debated the purpose, if any, of these so-called fixational eye movements, the largest of which are called microsaccades. Now the authors have demonstrated that microsaccades engender visibility when a person's gaze is fixed and that bigger and faster microsaccades work best. Microsaccades might also shed light on subliminal thoughts. Recent research suggests that the direction of microsaccades is biased toward objects to which people are unconsciously attracted, no matter where they are actually looking.

Teller, the mute half of the magician duo Penn & Teller, apparently pulls a coin out of thin air for the umpteenth time. The audience breaks into applause. It's another great performance in Las Vegas, Nevada -- only tonight, Teller is part of a special symposium hosted by the Association for the Scientific Study of Consciousness, bringing together magicians and cognitive scientists.

The Alternating Brightness Star (ABS) is an illusion that provides insight into the relationship between brightness perception and corner angle. Recent psychophysical studies of this illusion have shown that corner salience varies parametrically with corner angle, with sharp angles leading to strong illusory percepts and shallow angles leading to weak percepts. It is hypothesized that the illusory effects arise because of an interaction between surface corners and the shape of visual receptive fields: sharp surface corners may create hotspots of high local contrast due to processing by center-surround and other early receptive fields. If this hypothesis is correct, early visual neurons should respond powerfully to sharp corners and curved portions of surface edges. Indeed, the primary role of early visual neurons may be to localize the discontinuities along the edges of surfaces. If so, all early visual areas should show greater BOLD responses to sharp corners than to shallow corners. On the other hand, if corner processing is exclusively constrained to certain areas of the brain, only those specific areas will show greater responses to sharp vs shallow corners. To address this we explored the BOLD correlates of the ABS illusion in the human visual cortex using fMRI. We found that BOLD signal varies parametrically with corner angle throughout the visual cortex, offering the first neurophysiological correlates of the ABS illusion. This finding provides a neurophysiological basis for the previously reported psychophysical data that showed that corner salience varied parametrically with corner angle. We propose that all early visual areas localize discontinuities along the edges of surfaces, and that specific cortical corner-processing circuits further establish the specific nature of those discontinuities, such as their orientation.

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 visibility of simple unattended stimuli. We have established that spatiotemporal edges must be present for targets to be visible. These spatiotemporal edges must be encoded by transient bursts of spikes in the early visual system. If these bursts are inhibited, visibility fails. Target-correlated activity must rise within the visual hierarchy at least to the level of V3, and be processed within the occipital lobe, to achieve visibility. The specific circuits that maintain visibility are not yet known, but we have deduced that lateral inhibition plays a critical role in sculpting our perception of visibility, both by causing interactions between stimuli positioned across space, and also by shaping the responses to stimuli across time. Further, the studies have served to narrow the number of possible theories to explain visibility and visual masking. Finally, we have discovered that lateral inhibition builds iteratively in strength throughout the visual hierarchy, for both monoptic and dichoptic stimuli. Since binocular information is not integrated until inputs from the two eyes reach the primary visual cortex, it follows that the early visual areas contain differential levels of monoptic and dichoptic lateral inhibitions. We exploited this fact to discover that excitatory integration of binocular inputs occurs at an earlier level than interocular suppression. These findings are potentially fundamental to our understanding of all forms of binocular vision and to determining the role of binocular rivalry in visual awareness.

This book presents a collection of articles reflecting state-of-the-art research in visual perception, specifically concentrating on neural correlates of perception. Each section addresses one of the main topics in vision research today. Part 2: Fundamentals of Awareness, Multi-Sensory Integration and High-Order Perception covers topics from filling-in to visual awareness to crossmodal interactions. A variety of methodological approaches are represented, including single-neuron recordings, fMRI and optical imaging, psychophysics, eye movement characterization and computational modelling. The contributions will provide the reader with a valuable perspective on the current status of vision research, and more importantly, with critical insight into future research directions and the discoveries yet to come. (Description by Amazon.com)

This book presents a collection of articles reflecting state-of-the-art research in visual perception, specifically concentrating on neural correlates of perception. Each section addresses one of the main topics in vision research today. Volume 1 Fundamentals of Vision: Low and Mid-Level Processes in Perception covers topics from receptive field analyses to shape perception and eye movements. A variety of methodological approaches are represented, including single-neuron recordings, fMRI and optical imaging, psychophysics, eye movement characterization and computational modelling. The contributions will provide the reader with a valuable perspective on the current status of vision research, and more importantly, with critical insight into future research directions and the discoveries yet to come. (Description by Amazon.com)