Predictive Activity in Macaque Frontal Eye Field Neurons During Standard and Natural Scene Searching

Adam Phillips

doi:https://doi.org/10.21985/N2B735

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Predictive Activity in Macaque Frontal Eye Field Neurons During Standard and Natural Scene Searching

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Saccades are rapid eye movements that bring visual images into focus by placing them on the fovea. The control of accurate and precise saccades is essential for normal visual perception of the world around us. Disruptions in saccade production are the hallmark of several neurological disorders such as schizophrenia and autism. Uncontrollable saccades are even the root cause of some forms of reading dyslexia. There are many regions of our brains that work together to control different aspects of proper saccadic behavior, several of which are located in frontal cortex. The frontal eye field (FEF) is one of these regions, and while we understand some of its functions, others are still being investigated. The FEF is thought to be primarily responsible for the voluntary control of eye movements, but more recent studies have pointed towards other, non-motor related capabilities. The over-reaching goal of these experiments was to gain a better understanding of how the FEF functions as we search the world around us. Activity in the macaque FEF was studied as monkeys searched for learned targets in both simple displays and complex real-world images. We found that FEF cell activity that signals the direction of an impending saccade to a target object among several distracting ones does not depend upon sensory-like responses that occur when objects appear suddenly. In addition, while searching natural images, FEF activity changes after each saccade to indicate the direction of the next eye movement. The timing of this change is very early, and occurs before objects in an FEF cell's response-field can be processed by the FEF. Lastly, we found a subset of FEF cells that also modulate their activity to predict the vector and spatial endpoint of the saccade-after-next. These results suggest that while searching the world, the FEF functions in part to plan series of eye movements or to direct attention covertly to areas of interest during the search, but not as a processor of sensory information.

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