Posteromedial Cortex Shapes how Stimuli are Represented During Working Memory
Post by Lina Teichmann
The takeaway
The posteromedial cortex (PMC) plays a key role during visuospatial working memory tasks. The results of the current study suggest that the PMC is specifically involved in shaping stimulus representations when people are maintaining the spatial layout of different objects.
What's the science?
The PMC has been shown to be involved in visuospatial working memory tasks. In particular, prior work has shown that the PMC is centrally involved in the representation and integration of a variety of information during working memory. This week in the Journal of Neuroscience, Goddard and colleagues examined what particular function the PMC serves in working memory.
How did they do it?
Using Magnetoencephalography (MEG), a non-invasive neuroimaging method with a high temporal resolution, the authors recorded brain activity while participants performed a visuospatial working memory task. In particular, participants viewed four sequentially presented objects that appear in different locations on the screen. After a maintenance period, participants were then shown an object at one location and had to indicate whether this object-location combination had appeared in the sequence.
Using source-localization, brain activation patterns were extracted within different regions of interest. In particular, the authors focused on the occipital cortex, centrotemporal cortex, PMC, and prefrontal cortex. A classifier (a specific type of computer algorithm) was then trained to distinguish the pattern of brain activation evoked by viewing the different stimuli. This analysis gives us an indication of whether information about the stimulus location and identity is represented in a given region of interest. Then, Granger causality was used to examine the direction of information flow between these regions to test what type of information is relayed by PMC during working memory.
What did they find?
The findings demonstrate that object representations found in PMC have an effect on representations in the other regions of interest in the brain. In particular, the information in PMC had a strong influence on the object representation in prefrontal areas, highlighting that PMC is responsible to relay information that is needed for successful recall.
What's the impact?
Overall, the findings here provide an important step towards understanding the concrete role of the PMC by highlighting that it relays remembered information to other brain regions during visuospatial working memory. As PMC dysfunction has been connected to Alzheimer’s disease, it is crucial to understand its functional role in the healthy brain.