Sensory modality- and load-dependent changes across cortical working memory representations

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Working Memory Research

Background:

• Distributed cortical areas are known to represent working memory (WM) contents.
• The necessity of these areas for memory maintenance, especially under varying loads, remains debated.

Purpose of the Study:

• To investigate how maintaining multiple items affects neural information across cortical regions.
• To examine the differential impact of sensory modality and visual load on working memory representations.

Main Methods:

• Functional magnetic resonance imaging (fMRI) experiment with 81 participants.
• Participants memorized two items (orientation or pitch) for 13.8 seconds.
• Manipulated sensory modality to vary visual load while keeping overall WM load constant.

Main Results:

• Significant orientation information was found in visual, parietal, and frontal areas.
• Increased visual load decreased behavioral recall and orientation-specific information in the visual cortex.
• Parietal areas showed early delay effects, while frontal representations remained unaffected by load.

Conclusions:

• Visual cortices share the labor of representing information, with increased load reducing representational fidelity.
• Anterior cortical areas represent multiple items robustly but with reduced precision.
• Multivoxel pattern analysis suggests a drop in mnemonic information representation with increased load.