Cortical Representations of Visual Stimuli Shift Locations with Changes in Memory States

Area of Science:

• Neuroscience
• Cognitive Science
• Memory Research

Background:

• Episodic memory retrieval typically involves reactivating neural patterns from encoding.
• However, content representations can differ between encoding and retrieval stages.
• Real-world scenarios often involve intrinsic biases toward either encoding or retrieval, independent of task demands.

Purpose of the Study:

• To investigate if intrinsic memory states, separate from task instructions, dictate the cortical location of memory content representations.
• To determine if these intrinsic states influence the brain regions involved in memory encoding versus retrieval.

Main Methods:

• A human functional magnetic resonance imaging (fMRI) study with 33 participants.
• Participants viewed object images and were instructed to either encode the current object or retrieve a similar object.
• Pattern classifiers were used to decode memory states from attentional networks.

Main Results:

• Biases toward encoding or retrieval were reflected in large-scale attentional networks.
• Decoded memory states predicted shifts in object representations from visual cortex (encoding) to ventral parietal cortex (retrieval).
• Differential connectivity between visual/ventral parietal cortices and the hippocampus was observed during encoding versus retrieval.

Conclusions:

• Intrinsic biases toward memory encoding or retrieval significantly influence the cortical areas expressing content information.
• The hippocampus appears to mediate these shifts in content representations across cortical regions.
• These findings highlight the role of intrinsic brain states in shaping memory processes.