Attention and Memory-Related Responses of Neurons in the Lateral Intraparietal Area During Spatial and Shape-Delayed Match-to-Sample Tasks

TLDR

In the lateral intraparietal area, neuronal activity changes when a monkey attends to, remembers, and looks toward targets, yet prior work attributing such responses to active processes may actually reflect more passive processing. The study recorded isolated neurons while monkeys performed spatial and shape match‑to‑sample tasks to examine voluntary active processes in LIP. Neurons were recorded in isolated units while monkeys performed spatial and shape match‑to‑sample tasks. Many LIP neurons exhibited spatially selective delay activity that was task‑independent, while a minority showed instruction‑dependent activity, and some units displayed stronger shape‑specific responses during shape‑matching tasks, indicating feature‑based attention in LIP—a phenomenon not previously described in primate cortex.

Abstract

When a monkey attends to, remembers, and looks toward targets, the activity of some neurons in the lateral intraparietal area (LIP) changes. We recorded from isolated neurons during both a spatial and a shape match-to-sample task to examine and characterize voluntary active processes in LIP. Many LIP neurons show spatially selective activity during the delay period that depends on the location of the sample, but for most cells, this activity does not differ between the two tasks. Although much past work in posterior parietal cortex has explained responses in this region in terms of active processes such as decision-making and motor planning, our findings suggest that much of that activity represents more passive processing. Nevertheless, we do see a significant minority of units that demonstrate instruction-dependent activity during the delay period, suggesting that these units could represent the neural correlates of voluntary or active processes. Separately, we found that during the presentation of the sample stimulus and test array, some units show stronger responses to the stimulus in the shape-matching task when the animal must attend to the shape of a stimulus. This elevated response to the sample during the shape task provides evidence for feature-based attention in LIP. Attention to shape is a property that has not previously been described in primate cortex.