Our research focuses on understanding the neural bases of our visual experience. How can the electrical activity of a neuron, or a neuronal population, convey the color or brightness of an object? How can we determine the signal from the noise in a train of electrical impulses within a neuron? What type of neural code do neurons use to communicate information to each other? How are neural impulses grouped to represent the different features of a visual scene? To address these questions we use a combination of techniques, including fMRI, electrophysiological recordings from single neurons, psychophysical measurements, and computational models of visual function.
Most of our visual experience is driven by the eye movements we produce while we fixate our gaze. In a sense, our visual system thus has a built-in contradiction: when we direct our gaze at an object of interest, our eyes are never still. Therefore the perception, physiology, and computational modeling of fixational eye movements is critical to our understanding of vision in general, and also to the understanding of the neural computations that work to overcome neural adaptation in normal subjects as well as in clinical patients. Moreover, because we are not aware of our fixational eye movements, they can also help us understand the underpinnings of visual awareness. Over the last decade, we have studied the neuronal and perceptual correlates of fixational eye movements. Our long-term objectives are to build on our previous discoveries concerning the neural activity driven by fixational eye movements, and to also discover the oculomotor basis for generating fixational eye movements. We have moreover begun to study the importance of fixational eye movements for visual perception in normal vision and in visual disease.
What types of visual features are most salient to the brain? How do visual neurons combine stimulus features, such as edges and corners, into whole objects? To answer these questions, we have presented various kinds of visual stimuli while monitoring the activity in visual neurons. We have found that corners generate more salient perception and more powerful neural responses than edges. This discovery has great potential consequences for our understanding of visual functional anatomy. With studies such as these, our lab is helping to determine the basic building blocks of vision–from simple to more complex stimuli– that construct our perception of brightness and shape. This work promises to help develop ophthalmic techniques to overcome deficits in low vision, by improving the salience of stimuli. (See demo).