Distinct Neural Substrates for Maintaining Locations and Spatial Relations in Working Memory

Abstract

Previous work has demonstrated a distinction between maintenance of two types of spatial information in working memory (WM): spatial locations and spatial relations. While a body of work has investigated the neural mechanisms of sensory-based information like spatial locations, little is known about how spatial relations are maintained in WM. In two experiments, we used fMRI to investigate the involvement of early visual cortex in the maintenance of spatial relations in WM. In both experiments, we found less quadrant-specific BOLD activity in visual cortex when a single spatial relation, compared to a single spatial location, was held in WM. Also across both experiments, we found a consistent set of brain regions that were differentially activated during maintenance of locations vs. relations. Maintaining a location, compared to a relation, was associated with greater activity in typical spatial WM regions like posterior parietal cortex and prefrontal regions. Whereas maintaining a relation, compared to a location, was associated with greater activity in the parahippocampal gyrus and precuneus/retrosplenial cortex. Further, in Experiment 2 we manipulated WM load and included trials where participants had to maintain three spatial locations or relations. Under this high load condition, the regions sensitive to locations vs. relations were somewhat different than under low load. We also identified regions that were sensitive to load specifically for location or relation maintenance, as well as overlapping regions sensitive to load more generally. These results suggest that the neural substrates underlying WM maintenance of spatial locations and relations are distinct from one another and that the neural representations of these distinct types of spatial information change with load.

Load effects on spatial working memory performance are linked to distributed alpha and beta oscillations

“…Finally, retrieval refers to the recall and application of the information to achieve a cognitive goal. Previous functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) investigations have demonstrated that a bilateral network of predominantly frontal and parietal brain regions is implicated in SWM processes, and that activity within this network tends to scale with WM load (i.e., the number of items held in WM; Bauer, Sammer, & Toepper, 2015;Blacker & Courtney, 2016;Bollmann et al, 2015;Cabeza & Nyberg, 2000;Curtis, 2006;Fusser et al, 2011;Glahn et al, 2002;Harrison, Jolicoeur, & Marois, The data that support the findings of this study are available from the corresponding author upon reasonable request. 2010; Huang et al, 2016;Leung, Seelig, & Gore, 2004;Magen, Emmanouil, McMains, Kastner, & Treisman, 2009;Nagel et al, 2009;Nee et al, 2013;Rottschy et al, 2012;Srimal & Curtis, 2008;Todd & Marois, 2004;Toepper et al, 2014).…”

Keeping track of where we are: Spatial working memory in navigation

“…The imaginary line manipulation in the low load trials was necessary to equate the number of sample circles displayed for Location and Relation trials. Further, previous work using this task has shown that the load manipulation for Location trials activates brain regions that are typically found with load increases in other types of visuospatial WM (Blacker & Courtney, 2016), such as posterior parietal cortex (e.g., Todd & Marois, 2004) and frontal eye fields (e.g., Leung, Seelig, & Gore, 2004).…”

“…Participants also completed a novel WM task that required participants to either maintain spatial relations or spatial locations (Figure 3). This task was modeled after the tasks used in previous studies (Ackerman & Courtney, 2012; Blacker & Courtney, 2016; Ikkai et al, 2014).…”

“…Within the spatial domain, it is possible to maintain an absolute spatial coordinate of an object (i.e., a spatial location) or the relative position of an object (i.e., a spatial relation). In fact, recent evidence suggests that maintaining spatial locations is supported by distinct neural correlates from those involved in maintaining spatial relations (Ackerman & Courtney, 2012; Blacker & Courtney, 2016; Blacker, Ikkai, Lakshmanan, Ewen, & Courtney, 2016; Ikkai, Blacker, Lakshmanan, Ewen, & Courtney, 2014). Using functional magnetic resonance imaging (fMRI), Ackerman and Courtney (2012) found that relation WM was supported by activity in anterior portions of prefrontal and parietal regions, whereas location WM was associated with activity in more posterior portions of these same regions.…”

N-back Versus Complex Span Working Memory Training

“…Matrix reasoning tasks that are typically used to assess Gf also involve extracting relational information between stimuli (Carpenter, Just, & Shell, 1990). Previous work from our group has demonstrated a neural dissociation between maintaining concrete and relational information in WM (Ackerman & Courtney, 2012; Blacker & Courtney, 2016; Blacker, Ikkai, Lakshmanan, Ewen, & Courtney, 2016; Ikkai, Blacker, Lakshmanan, Ewen, & Courtney, 2014). Specifically, these studies have shown that maintaining a concrete piece of sensory information, such as a spatial location, is supported by distinct neural substrates as compared to maintaining a spatial relationship that is independent of the original sensory location.…”