In the Unit on Perception and Action we investigate how visual inputs are transformed into perception and behavior. Most of our research has been focused on the frontal eye field (FEF), an area in the prefrontal cortex that converts visual information into eye movement commands. We have shown that FEF combines visual inputs with cognitive knowledge to form a priority map of visual space that identifies the location of the most important objects in the visual scene to guide gaze. During the past year we have extended this finding to show that FEF anticipates future locations in which important visual stimuli will appear (Ref 1). In a collaborative study, we investigated how the visuomotor system reacts to sudden changes in the visual scene that require a dynamic change in saccade planning (Ref 2). In addition, we have recently submitted 3 papers (currently under review) that describe results from our investigations on how spatially selective signals in the frontal cortex enhance visual processing leading to object recognition and complex object representations in the inferior temporal cortex. In ref. 1 we addressed the question of how cognitive processes control spatial attention in the absence of visual input. We recorded frontal eye field activity in monkeys trained to perform a difficult discrimination task in which the monkeys attended the locations of the visual stimuli to be discriminated before they actually appeared. We found that most FEF neurons exhibited elevated activity when a cue informed the monkey that a stimulus would appear. This anticipatory attention-related activity in FEF occurred without any visual stimulation and was not related to motor processes. Together, these studies demonstrate that stimulus-driven and cognitively-driven spatial attention signals are present in FEF and are independent of saccade command signals. Therefore, FEF probably serves an important role in controlling visual spatial attention in addition to its well known role in saccade production. In ref. 2 we investigated the dynamics of visual selection and saccade preparation in the FEF of monkeys performing a search-step task combining the classic double-step saccade task with visual search. Reward was earned for producing a saccade to a color singleton. On random trials the target and one distractor swapped locations before the saccade and monkeys were rewarded for shifting gaze to the new singleton location. Chronometric analyses of the neural responses to the target step revealed that the modulation of visually responsive neurons and movement-related neurons occurred early enough to shift attention and saccade preparation from the old to the new target location. These findings indicate that visual activity in the frontal eye field signals the location of targets for orienting, whereas movement-related activity instantiates saccade preparation. These studies have extended our understanding of visual processing. We have shown that the frontal eye field provides top-down cognitively-derived signals that modulate ongoing visual processing. We also have identified two separate and dissociable cognitive processes within the frontal eye field, visual selection and saccade preparation. Both of these processes are crucial for normal vision and for interacting with the world. With this knowledge we can design experiments to investigate the flow of sensory information through the brain as it is transformed into perception and action. This work helps us understand the mechanisms of how the brain focuses attention to make perceptual decisions and guide behavior, which is necessary to be able to understand and treat eye movement and attention-related disorders in humans.
