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

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.

Relationship between Neural Responses and Visual Grouping in the Monkey Parietal Cortex

“…Because we did not employ this task, we do not know whether the recordings made in the present study were from within the AIP or LIP. Judging from the reported stereotaxic coordinate of these areas (Toth and Assad, 2002;Sereno and Amador, 2006;Borra et al, 2008;Janssen et al, 2008), our recording site (A3-P4) seems mainly situated in the anterior part of LIP and possibly includes a part of AIP. Important functional aspects of neurons within those two areas are activities related to saccadic eye movements or complex hand manipulation.…”

Enhancement of Object Representations in Primate Perirhinal Cortex During a Visual Working-Memory Task

“…On the other hand, it is more difficult to exclude the possibility of a contribution from object attention, if indeed working memory for objects and selective attention for objects are independent mechanisms. It is well established that attention can select features or objects nonspatially as demonstrated psychophysically Duncan 1984;Lee and Chun 2001;Vecera and Farah 1994), neurophysiologically (Chelazzi et al 1993;Hayden and Gallant 2005;McAdams and Maunsell 2000;Motter 1994a;Sereno and Amador 2006;Treue and Trujillo 1999) and by brain imaging (Corbetta et al 1991;Liu et al 2003;O'Craven et al 1999;Serences et al 2004).…”

“…On one hand, there is the view that prefrontal delay activity actually represents the contents of working memory, including specific stimulus features (reviewed by Courtney 2004). By this view, representations in visual working memory do not engage the same posterior neural structures that are involved in perceptual representations of stimuli.…”

Coding of Shape and Position in Macaque Lateral Intraparietal Area

“…Her dorsal visual stream was able to compute the orientation of the slot or the shape of the object (James et al, 2003) and adjusted her hand accordingly. Anterior intraparietal (AIP) neurons respond selectively to real-world objects (Sakata et al, 1995;Murata et al, 2000), and a large proportion of lateral intraparietal (LIP) neurons shows shape-selective responses (Sereno and Maunsell, 1998;Sereno and Amador, 2006). Lehky and Sereno (2007) reported a greater degree of shape selectivity in IT than in LIP.…”