The role of the lateral intraparietal area of the monkey in the generation of saccades and visuospatial attention

ABSTRACT: The brain cannot monitor or react towards the entire world at a giv-en time. Instead, using the process of attention, it selects objects in the world for further analysis. Neuronal activity in the monkey intraparietal area has the properties appropriate for a neuronal substrate of attention: instead of all objects being represented in the parietal cortex, only salient objects are. Such objects can be salient because of their physical properties (recently flashed ob-jects or moving objects) or because they can be made important to the animal by virtue of a task. Although lateral intraparietal area (LIP) neurons respond through the delay period of a memory-guided saccade, they also respond in an enhanced manner to distractors flashed during the delay period of a memory-guided saccade being generated to a position outside the receptive field. This activity parallels the monkey’s psychophysical attentional process: attention is ordinarily pinned at the goal of a memory-guided saccade, but it shifts briefly to the locus of a task-irrelevant distractor flashed briefly during the delay pe-riod and then returns to the goal. Although neurons in LIP have been implicat-ed as being directly involved in the generation of saccadic eye movements, their activity does not predict where, when, or if a saccade will occur. The ensemble of activity in LIP, however, does accurately describe the locus of attention