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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.


Behavioral results illustrating accuracy (left) and RT (right). Error bars represent standard error of the mean. ∗p < 0.01.
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Figure 3: Behavioral results illustrating accuracy (left) and RT (right). Error bars represent standard error of the mean. ∗p < 0.01.

Mentions: To assess behavioral performance on our WM task, we tested paired-samples t-tests on accuracy and response time (RT) comparing Relation vs. Location trials (Figure 3). Results demonstrated no significant difference in RT between Relation and Location trials, t(24) = 0.46, p = 0.65. However, a significant difference in accuracy did emerge, t(24) = 3.02, p < 0.01, with accuracy being higher for Relation trials. While these accuracy results do suggest that Location trials were more difficult than Relation trials, the most important feature of our design is that in both trial types, participants were asked to encode and maintain only one piece of information (i.e., one location or one relation) and fMRI data was only analyzed for correct trials. Also, as can be seen in Figure 3, performance overall was quite high across both trial types.


Distinct Neural Substrates for Maintaining Locations and Spatial Relations in Working Memory
Behavioral results illustrating accuracy (left) and RT (right). Error bars represent standard error of the mean. ∗p < 0.01.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: Behavioral results illustrating accuracy (left) and RT (right). Error bars represent standard error of the mean. ∗p < 0.01.
Mentions: To assess behavioral performance on our WM task, we tested paired-samples t-tests on accuracy and response time (RT) comparing Relation vs. Location trials (Figure 3). Results demonstrated no significant difference in RT between Relation and Location trials, t(24) = 0.46, p = 0.65. However, a significant difference in accuracy did emerge, t(24) = 3.02, p < 0.01, with accuracy being higher for Relation trials. While these accuracy results do suggest that Location trials were more difficult than Relation trials, the most important feature of our design is that in both trial types, participants were asked to encode and maintain only one piece of information (i.e., one location or one relation) and fMRI data was only analyzed for correct trials. Also, as can be seen in Figure 3, performance overall was quite high across 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.