Neural Mechanisms of Fixation Choice While Searching Natural Scenes

The overall goal of these experiments is to understand how the brain controls where we look. To accomplish this, it is important to study brain activity and behavior under conditions that closely approximate those in the real world. All of the experiments we propose to do will use awake behaving rhesus monkeys as subjects. Our work focuses upon the frontal eye field (FEF) a region of cerebral cortex shared by both human and non-human primates that is closely involved in the control of purposive voluntary eye movements. Past work by our laboratories and many others, has helped us to learn a great deal about the FEF’s role in controlling single saccades to a limited number of potential targets. However, its role in the generation of eye movement strategies involving continuous series of self-generated eye movements in the target rich environment of a natural environment is poorly understood. The experiments described in this proposal use semi-chronic arrays of microelectrodes to record single neuron activity from the FEF while monkeys search for objects in natural scenes. The power of this design is that we can observe the activities of many single neurons while the monkey makes series of self-guided eye movements in search of the target object. Our preliminary data, suggests that the activities of FEF neurons are directly related to the development and execution of eye movement strategies to optimize these search movements. The activities we see are related to 1) planning efficient search movements, 2) selecting the location of the search target, and 3) controlling both exploratory and goal-directed saccades. The Aims of this proposal will use this preliminary data as a foundation to 1) Understand both the behavioral mechanisms and underlying neural activity responsible for planning efficient search eye movements. 2) Investigate how search targets are detected and represented by the FEF. And 3) investigate the neural activity controlling the exploratory eye movements used to survey the visual environment, and compare this activity to that responsible for the exploitative eye movements that capture the ultimate target of the search. The contribution of the proposed research will be significant because it will spearhead the use of natural scene search to study how the FEF is involved in eye movement strategies, including the development of both the data analysis and the experimental techniques needed to do so. It will lead to a deeper understanding of the FEF, the generation of real world eye movement strategies, and the data analysis techniques needed to make sense of complicated multivariate data.