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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.


Whole-brain results showing regions that were significantly more active for High vs. Low load during the WM delay period. Blue regions are areas sensitive to load for Location trials only. Red regions are areas sensitive to load for Relation trials only. Purple regions are overlapping regions that were sensitive to load for both trial types. Regions that showed a significant load × trial type interaction are outlined in white. Abbreviations: inferior parietal lobule (IPL) and inferior precentral sulcus (inf-PCS).
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Figure 9: Whole-brain results showing regions that were significantly more active for High vs. Low load during the WM delay period. Blue regions are areas sensitive to load for Location trials only. Red regions are areas sensitive to load for Relation trials only. Purple regions are overlapping regions that were sensitive to load for both trial types. Regions that showed a significant load × trial type interaction are outlined in white. Abbreviations: inferior parietal lobule (IPL) and inferior precentral sulcus (inf-PCS).

Mentions: We tested a load x trial type interaction using AFNIs 3dANOVA3 command to determine regions that were sensitive to load differentially for each trial type. Figure 9 shows a conjunction map of regions sensitive to load for Relation trials, Location trials, and overlapping regions sensitive to load for both trial types. Regions that showed a significant load × trial type interaction are outlined in white in Figure 9 and included bilateral IPL, left inf-PCS, bilateral cuneus, right marginal sulcus, left cingulate sulcus, and a left subcortical region. The bilateral IPL regions were sensitive to load only for Relation trials. The left inf-PCS region was also mostly sensitive to load for Relation trials (shown in red), but showed a small portion that was sensitive to load for both trial types (shown in purple). Finally, the bilateral cuneus regions were sensitive to load for Relation trials only, consistent with our trial type contrasts discussed above. While only these particular regions showed a significant load × trial type interaction, Figure 9 shows all regions that were sensitive to load for Relation, Location, and both trial types.


Distinct Neural Substrates for Maintaining Locations and Spatial Relations in Working Memory
Whole-brain results showing regions that were significantly more active for High vs. Low load during the WM delay period. Blue regions are areas sensitive to load for Location trials only. Red regions are areas sensitive to load for Relation trials only. Purple regions are overlapping regions that were sensitive to load for both trial types. Regions that showed a significant load × trial type interaction are outlined in white. Abbreviations: inferior parietal lobule (IPL) and inferior precentral sulcus (inf-PCS).
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Related In: Results  -  Collection

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

Figure 9: Whole-brain results showing regions that were significantly more active for High vs. Low load during the WM delay period. Blue regions are areas sensitive to load for Location trials only. Red regions are areas sensitive to load for Relation trials only. Purple regions are overlapping regions that were sensitive to load for both trial types. Regions that showed a significant load × trial type interaction are outlined in white. Abbreviations: inferior parietal lobule (IPL) and inferior precentral sulcus (inf-PCS).
Mentions: We tested a load x trial type interaction using AFNIs 3dANOVA3 command to determine regions that were sensitive to load differentially for each trial type. Figure 9 shows a conjunction map of regions sensitive to load for Relation trials, Location trials, and overlapping regions sensitive to load for both trial types. Regions that showed a significant load × trial type interaction are outlined in white in Figure 9 and included bilateral IPL, left inf-PCS, bilateral cuneus, right marginal sulcus, left cingulate sulcus, and a left subcortical region. The bilateral IPL regions were sensitive to load only for Relation trials. The left inf-PCS region was also mostly sensitive to load for Relation trials (shown in red), but showed a small portion that was sensitive to load for both trial types (shown in purple). Finally, the bilateral cuneus regions were sensitive to load for Relation trials only, consistent with our trial type contrasts discussed above. While only these particular regions showed a significant load × trial type interaction, Figure 9 shows all regions that were sensitive to load for Relation, Location, and both trial types.

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.