Memory Traces Reflect How They Were Last Accessed

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Memory Research

Background:

• Episodic memories are dynamic and alter with each retrieval event.
• The way semantic knowledge is accessed during episodic retrieval may influence subsequent memory representations.

Purpose of the Study:

• To investigate how different semantic access levels (item, category, theme) during episodic retrieval affect neural representations during recognition.
• To determine if prior semantic access history leaves measurable neural traces in brain regions involved in memory.

Main Methods:

• Functional magnetic resonance imaging (fMRI) study with human participants.
• Participants learned novel word-image pairs and underwent re-exposure accessing semantic knowledge at item, category, or theme levels.
• A subsequent recognition task assessed memory performance and neural activity patterns.

Main Results:

• Behavioral memory performance was equivalent across semantic access conditions.
• Neural activity during recognition differed based on prior semantic access history, decodable in visual cortex and hippocampus.
• Category-level access enhanced neural similarity in early visual cortex; item-level access increased representational differentiation in the visual word form area.

Conclusions:

• The method of accessing semantic knowledge during episodic retrieval leaves distinct neural signatures.
• Semantic-episodic interactions dynamically shape the neural representation of memories.
• Findings highlight the malleability of memory representations influenced by semantic processing during retrieval.