Dr. Krauzlis investigates the brain circuits that accomplish higher-order visual functions, including attention, perception, and object recognition. He is especially interested in how these visual functions are linked to goal-directed behavior, and how the properties of these circuits change as we explore and learn about our visual world. Dr. Krauzlis’ earliest work focused on the control of eye movements. As a graduate student, he developed one of the best-known computational models of smooth pursuit eye movements – the movements that allow us to smoothly track and inspect moving objects. His work explained how properties of pursuit eye movements are driven by visual processes and he identified how neurons in the cerebellar part of the brain convert visual signals into the motor commands that smoothly move the eyes. As a postdoc, Dr. Krauzlis asked how these pursuit eye movements were coordinated with saccades, the other type of eye movement that quickly redirects vision from point to point (for example, during reading). Previous work assumed that pursuit and saccades were completely different brain systems. In contrast, Dr. Krauzlis inferred that the process of deciding when and how to move the eyes required coordination between the two systems and shared neural mechanisms. This turned out to be correct, and the idea that “pursuit and saccades might be viewed as different outcomes resulting from a single cascade of sensory-motor functions” is now generally accepted and has replaced the older view of distinct oculomotor subsystems. As a principal investigator, Dr. Krauzlis provided insights into how we hold our eyes steady when looking at an object, and how we decide where to look next. He demonstrated that the ability to maintain stable eye fixation depends on the balance of activity in a map of visual space contained in the midbrain superior colliculus. Conversely, when the activity is unbalanced, this provides the necessary trigger to move the eyes. This “equilibrium” idea has supplanted previous notions about fixation motor commands and provides a basis for understanding clinical cases of fixational instability. These experiments also explained the generation of “microsaccades”, the miniscule eye movements that occur when we hold our gaze fixed at one point. His lab identified the basic brain mechanisms responsible for the generation of microsaccades and showed that these mechanisms are the same as those for larger saccades; it is now accepted that microsaccades and larger saccades are controlled by fundamentally the same brain circuits. This line of work also revealed that saccades and pursuit eye movements share a common neural mechanism for selecting the next target, explaining how we seamlessly coordinate these very different eye movements during natural viewing. Dr. Krauzlis’ interest in how we decide where to look led naturally to questions about how we control our visual attention. Most work on visual attention has focused on the neocortex, the mantle of tissue on the visible surface of the brain. In contrast, Dr. Krauzlis demonstrated that visual attention also depends crucially on the midbrain superior colliculus, an evolutionarily conserved brain structure present in all vertebrates that is important for how animals orient in their environment. This work showed that the superior colliculus is important for the internal orienting of attention, beyond its role in the physical orienting of the body. Remarkably, the contribution of the superior colliculus can be dissociated from the well-known signatures of attention in the visual neocortex. This initially controversial finding has now led to acceptance of the idea that attention depends on the interaction of cortical and subcortical brain circuits. One possibility being actively explored in the lab is that this subcortical circuit provides a shortcut for rapidly identifying potential objects that are then prioritized for more elaborate processing by the neocortex. In support of this idea, taking advantage of the unique collaborative environment of the Intramural Research Program at NIH, the lab has used a combination of functional imaging and causal manipulations to uncover a novel area in the temporal visual cortex that is functionally linked to these subcortical attention circuits. This area may be homologous to the temporo-parietal region in humans that is implicated in spatial neglect caused by stroke, illustrating the importance of animal models for understanding high-level functions of the human brain. More recently, the importance of these midbrain circuits has led Dr. Krauzlis to examine another set of evolutionarily conserved circuits that pass through the basal ganglia, a set of brain structures involved in reward-based learning that are implicated in wide range of neurological disorders in humans, including Parkinson’s. The rationale behind this line of work is that high-level visual functions like attention are not innate or fixed but depend on learning that takes place as we interact with our environment. Testing these ideas is especially challenging because the circuits through the basal ganglia are extraordinarily complex and targeting the underlying circuits requires tools that operate with genetic and cellular precision. Accordingly, Dr. Krauzlis has developed an experimental approach for studying visual attention in mice and, by applying the techniques available in this animal model, has shown that circuits through the basal ganglia are involved in the control of visual attention and the learning of flexible visual behaviors. This work has started to influence thinking about the role of the basal ganglia in perceptual and cognitive functions and, conversely, the importance of reward-based learning in those higher-order functions.
Dr. Krauzlis graduated summa cum laude from Princeton University with a degree in Biology in 1985 and received his Ph.D. in Neuroscience in 1991 from the University of California, San Francisco, in Steve Lisberger's laboratory. After postdoctoral training with Fred Miles and Bob Wurtz at the National Eye Institute, he was recruited to the Salk Institute in 1997, where he was promoted to Full Professor in the Systems Neurobiology Laboratory. In 2011, Dr. Krauzlis returned to the National Eye Institute as a Senior Investigator where he established the Visual Circuits Section in the Laboratory of Sensorimotor Research (LSR). Dr. Krauzlis holds an Adjunct Professor position at the Salk Institute and a Joint Appointment with the National Institute on Drug Abuse (NIDA). He has been Lab Chief of the LSR since 2021.
- Bogadhi AR, Katz LN, Bollimunta A, Leopold DA, Krauzlis RJ. Midbrain activity shapes high-level visual properties in the primate temporal cortex. Neuron. 2021;109(4):690-699.e5.
- Yu G, Herman JP, Katz LN, Krauzlis RJ. Microsaccades as a marker not a cause for attention-related modulation. Elife. 2022;11.
- Bogadhi AR, Bollimunta A, Leopold DA, Krauzlis RJ. Spatial Attention Deficits Are Causally Linked to an Area in Macaque Temporal Cortex. Curr Biol. 2019;29(5):726-736.e4.
- Herman JP, Katz LN, Krauzlis RJ. Midbrain activity can explain perceptual decisions during an attention task. Nat Neurosci. 2018;21(12):1651-1655.
- Wang L, Krauzlis RJ. Involvement of Striatal Direct Pathway in Visual Spatial Attention in Mice. Curr Biol. 2020;30(23):4739-4744.e5.
Related Scientific Focus Areas
This page was last updated on Thursday, November 9, 2023