Mission Statement

Physiological recording in the LSR.

The ability to guide our movements under sensory control is one of the most critical of human abilities. Our use of this ability ranges from the mundane coordination needed in everyday life to the precision of athletic achievement. Disorders of this ability are devastating and cost billions of dollars in custodial health care. The goal of the Laboratory of Sensorimotor Research is to understand the fundamental brain mechanisms that allow such sensory-motor coordination. We concentrate on the system within the brain that is probably best understood in the control of such complex activities: the visual/oculomotor system. Our center of interest is how this system works in humans, both normally and when it fails as a result of disease or trauma. We are fortunate to have a superb animal model, the Rhesus monkey, which allows us to investigate the mechanisms within the brain related to the visual input, the oculomotor output, and the central processing that connects them.

Vision Section

Section Chief: Bruce G. Cumming, M.D., Ph.D. bgc@lsr.nei.nih.gov Action potentials generated by neurons in the cerebral cortex eventually give rise to conscious sensations. Understanding this process requires both a description of what information is represented in the activity of single neurons, and a description of the mechanism by which that representation is generated. Binocular stereopsis (the ability to perceive depth by combining images from the two eyes) is an attractive model system to study both the nature and mechanism of the cortical representation for several reasons:

• It seems likely that we can explain the mechanisms that underlie disparity selectivity in single neurons of the primary visual cortex.
• The psychophysical properties have been extensively studied in humans and monkeys. Many of these properties are not straightforwardly reflected in the activity of single neurons, at least in V1.
• Extensive computational work offers mechanisms that can bridge the gap between 1) and 2).
• Several lines of evidence indicate that neurons in extrastriate cortex are more closely linked to the perception of stereoscopic depth than V1 neurons. Understanding how these responses are derived from neurons in V1 may then lead to a mechanistic description of how the brain generated the signals that give rise to the perception of depth.

With a view to generating this description, we record action potentials from single cortical neurons in awake animals trained to perform stereoscopic discrimination tasks. Quantitative modelling is then used to describe both the response properties of individual neurons, and their relationship to psychophysical judgments.

Acuity Section

Section Chief: Edmond J. FitzGibbon, M.D. ejf@lsr.nei.nih.gov

Neural Modeling Section

Section Chief: Lance M. Optican, Ph.D. lmo@lsr.nei.nih.gov

This Section attempts to understand the neuronal and mechanical processes that underlie our ability to coordinate vision and action. This understanding is necessary to discover the root causes of, and ultimately find therapies for, a wide range of diseases that impair our ability to interact with the outside world. In neuroscience, as in all quantitative scientific fields, models are needed to discriminate amongst competing theories, guide experimental design, subdivide overall processes into their basic components, and generate quantitative predictions about the outcome of future experiments and potential therapies. The Section develops and tests mathematical models of sensory and motor function that are based on experimental and clinical observations. Our goal is to develop models with biological homologies that can establish a theoretical link between normal sensory and motor function and clinical deficits in vision and eye movements. Using this link, we can improve diagnosis and treatment of many clinical disorders.

Visual Motor Integration Section

Section Chief: Robert H. Wurtz, Ph.D. bob@lsr.nei.nih.gov

The Section on Visual Motor Integration studies the brain mechanisms that underlie visual perception and the visual control of movements, particularly eye movements. Experiments are directed toward understanding active vision, the vision that results from the interaction of visual and oculomotor systems within the brain. Recent experiments have concentrated on how information about impending eye movements (referred to as a corollary discharge) acts to compensate for the movements of the image on the retina that are produced with eye movements. Other interactions are related to the selection of aspects of the visual world to explore such as visual spatial attention. The goal is to identify neuronal circuits in the brain that provide the mechanisms for the visual functions.

Neuronal Networks Section

Section Chief: Okihide Hikosaka, M.D., Ph.D. oh@lsr.nei.nih.gov

Surrounded by many objects and creatures, you choose, reach out, and manipulate some of them. You do so habitually to carry out routine work or deliberately with a new goal in mind. Probably unbeknownst to you, these complex behaviors are guided by a simple behavior called saccadic eye movement by which the line of sight is shifted quickly from one object to another. Our goal of research is to understand the neuronal mechanisms that control the saccadic eye movement. It has been demonstrated that the saccadic eye movement is controlled by hierarchically organized neuronal networks. The different levels of the networks carry different signals, from the brainstem networks carrying reflexive signals to the prefrontal cortical networks carrying cognitive signals. How can these parallel networks be controlled? Our research has shown that there are inhibitory gating mechanisms in different areas in the brain which are capable of selectively allowing or nullifying the outputs of individual networks. A remarkable area among them is the basal ganglia which are equipped with powerful inhibitory and disinhibitory mechanisms. How then do the inhibitory-disinhibitory mechanisms work? What controls the mechanisms? We believe that answering these questions is crucial for understanding how the brain has evolved to achieve such complex tasks.

Section on Eye Movements and Visual Selection

Section Chief: Richard Krauzlis, Ph.D. richard.krauzlis@nih.gov

Vision is an active process that starts in the eye, but is mostly accomplished by circuits of neurons in the central visual system. Unlike a camera, which records images without understanding what is there, our brain actively constructs our perception of the world based upon what we know through experience, in addition to what we sense through our eyes. A crucial aspect of this process is the selective filtering of visual information, which is accomplished in two ways. The first is to move the eyes to control how images fall on the retina of the eye. The second is to internally select some of the visual signals for further processing, while excluding others - this is known as visual attention. The long-term goal of our section is to understand the brain mechanisms that mediate these processes of eye movements and attention. Our current work focuses on visual spatial attention, which is affected in several prevalent brain disorders, including autism and attention deficit hyperactivity disorder. Using a range of neurophysiological, computational, and cellular techniques, in humans, non-human primates and mice, we aim to understand how these neuronal circuits operate under normal conditions and to identify how breakdowns in these mechanisms cause disorders of sensory-motor coordination.

Sensation, Cognition and Action Section

Section Chief: Bevil R. Conway, Ph.D. bevil@nih.gov

The Sensation, Cognition and Action Section aims to answer three fundamental questions. What are the computational goals of sensation, perception and cognition? What are the neural circuits, structures and operations in humans that implement these goals? And how do these components get wired up? Obtaining this knowledge will not only deepen our understanding of the human mind/brain and how vision works but also generate new ideas for tackling mental illnesses. To address these questions we leverage a range of techniques, including psychophysics and MRI in humans; along with experiments in non-human primates using fMRI-guided microelectrode recording, fMRI-guided pharmacological blockade, microstimulation, tract-tracing, and computational modeling.