Although we perceive our visual environment as stable, the information our brain receives from our eyes is continually disrupted through blinks and saccadic eye movements. Despite this "choppy" input, the visual world appears smooth and continuous. A critical process that is thought to underlie this phenomenon of "perceptual stability" is visual working memory, which facilitates the online maintenance and manipulation of visual information. Specifically, visual working memory may help tie the information obtained from one fixation to the next, so that a scene may be integrated across successive views. Recent research has made substantial advances in determining the extent of the memory that is maintained across saccadic eye movements. However, the specific nature of how information is compared and integrated across successive views has gone largely unexplored, and will be the primary concern of this proposal. In this proposal, we will examine how representations of objects are updated across changes in the position of the eyes and the focus of attention. For example, imagine viewing a scene of a cluttered desk in which a monitor, keyboard, and telephone are all within view in a single fixation. Following an eye movement to the left, each of these objects will now appear in a more rightward retinal position and it is necessary to update the positions of these objects so that they may be seen as old objects in new positions rather than new objects. One unanswered question regarding this updating process is when it occurs. Does it occur after the second fixation is made or is it more dynamic occurring as the eye movement is being programmed and executed, but prior to the actual fixation? Here, we will use the human eventrelated potential (ERP) technique to monitor the maintenance of information in visual working memory across changes in retinal position to determine when the updating process occurs. Moreover, we will also examine how changes in the focus of spatial attention within a single fixation affect the maintenance of information held in visual working memory. Specifically, does attending a new object disrupt or alter the representations of the current contents of memory? The outcome of these initial studies may serve as a basis for understanding the ways in which neurological damage can affect a patient's ability to understand and interact with the objects and events in the world.

R03MH069672

2003-12-10

2005-11-30