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

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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.

No MeSH data available.


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Whole-brain results for the WM delay period shown by load. Data are shown separately for low and high load (above) and averaged across load (below). Maps illustrate brain areas that were significantly more active for Relation (warmer colors) or Location (cooler colors) trials. Abbreviations: frontal eye fields (FEF), superior frontal junction (SFJ), intraparietal sulcus (IPS), superior/inferior parietal lobule (S/IPL), inferior precentral sulcus (inf-PCS), retrosplenial cortex (RSC), and parahippocampal gyrus (PHG).
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Figure 8: Whole-brain results for the WM delay period shown by load. Data are shown separately for low and high load (above) and averaged across load (below). Maps illustrate brain areas that were significantly more active for Relation (warmer colors) or Location (cooler colors) trials. Abbreviations: frontal eye fields (FEF), superior frontal junction (SFJ), intraparietal sulcus (IPS), superior/inferior parietal lobule (S/IPL), inferior precentral sulcus (inf-PCS), retrosplenial cortex (RSC), and parahippocampal gyrus (PHG).

Mentions: For the whole-brain analysis we were interested in two main contrasts: (1) regions sensitive to maintaining spatial locations vs. relations and (2) regions sensitive to load for each trial type. First, to find cortical areas that were more sensitive to maintaining either a spatial relation(s) or a spatial location(s) in WM, we contrasted Relation vs. Location trial delay period activity for low and high load separately (Figure 8). For low load, we found that bilateral IPS/SPL/IPL, bilateral FEF/SFJ, and left inf-PCS were more active for Location trials compared to Relation trials. We also found that left precuneus/RSC and bilateral PHG and cuneus were more active for Relation trials compared to Location trials. These results replicate the findings in Experiment 1. We did find additional regions sensitive to Location and Relation trials that were not present in Experiment 1 (see Figure 8; Table 2). These regions may have emerged due to increased power in Experiment 2 due to a larger sample size and/or from the slight modifications made to the task to accommodate the load manipulation.


Distinct Neural Substrates for Maintaining Locations and Spatial Relations in Working Memory
Whole-brain results for the WM delay period shown by load. Data are shown separately for low and high load (above) and averaged across load (below). Maps illustrate brain areas that were significantly more active for Relation (warmer colors) or Location (cooler colors) trials. Abbreviations: frontal eye fields (FEF), superior frontal junction (SFJ), intraparietal sulcus (IPS), superior/inferior parietal lobule (S/IPL), inferior precentral sulcus (inf-PCS), retrosplenial cortex (RSC), and parahippocampal gyrus (PHG).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121279&req=5

Figure 8: Whole-brain results for the WM delay period shown by load. Data are shown separately for low and high load (above) and averaged across load (below). Maps illustrate brain areas that were significantly more active for Relation (warmer colors) or Location (cooler colors) trials. Abbreviations: frontal eye fields (FEF), superior frontal junction (SFJ), intraparietal sulcus (IPS), superior/inferior parietal lobule (S/IPL), inferior precentral sulcus (inf-PCS), retrosplenial cortex (RSC), and parahippocampal gyrus (PHG).
Mentions: For the whole-brain analysis we were interested in two main contrasts: (1) regions sensitive to maintaining spatial locations vs. relations and (2) regions sensitive to load for each trial type. First, to find cortical areas that were more sensitive to maintaining either a spatial relation(s) or a spatial location(s) in WM, we contrasted Relation vs. Location trial delay period activity for low and high load separately (Figure 8). For low load, we found that bilateral IPS/SPL/IPL, bilateral FEF/SFJ, and left inf-PCS were more active for Location trials compared to Relation trials. We also found that left precuneus/RSC and bilateral PHG and cuneus were more active for Relation trials compared to Location trials. These results replicate the findings in Experiment 1. We did find additional regions sensitive to Location and Relation trials that were not present in Experiment 1 (see Figure 8; Table 2). These regions may have emerged due to increased power in Experiment 2 due to a larger sample size and/or from the slight modifications made to the task to accommodate the load manipulation.

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus