The neural instantiation of a priority map

Abstract

The term priority map is commonly used to describe a map of the visual scene, in which objects and locations are represented by their attentional priority, which itself is a combination of low-level salience and top-down control. The aim of this review is to examine how such a map may be represented at the neuronal level. We propose that there is not a single, common map in the brain, but that a number of cortical areas work together to generate the resultant behavior. Specifically, we suggest that the lateral intraparietal area (LIP) of posterior parietal cortex provides a simple representation of attentional priority, which remaps across saccades, so that there is an apparent allocentric map in a region with retinocentric encoding scheme. We propose that the frontal eye field (FEF) of prefrontal cortex receives the responses from LIP, but can suppress them to control the flow of eye movement behavior, and that the intermediate layers of the superior colliculus (SCi) reflect the final saccade goal. Together, these areas function to guide eye movements and may play a similar role in allocating covert visual attention.

Figure 1.

A hypothetical priority map (right panel) in response to an array of stimuli (left panel) in which the subject is asked to find a circle. Each stimulus is represented by a response. The popout (yellow triangle) is represented by a slightly higher response due to its low level salience and the circle is represented by a much higher response as this represents the goal of the task, i.e. a top down input. Note that top down influences are not limited to task rules and goals; in natural behavior they can be driven by influences such as experience, saccade plans, memories and expectations.