The left prefrontal cortex determines relevance at encoding and governs episodic memory formation.

Area of Science:

• Neuroscience
• Cognitive Psychology

Background:

• Hemispheric lateralization in the prefrontal cortex is crucial for memory, but its specific role in episodic memory, especially for emotional content, remains debated.
• Understanding the distinct contributions of the left and right prefrontal cortex is key to deciphering memory formation processes.

Purpose of the Study:

• To investigate the role of left and right dorsolateral prefrontal cortex (DLPFC) in episodic memory formation.
• To determine how modulating DLPFC activity impacts encoding and recall of semantically processed and emotionally valenced information.

Main Methods:

• A randomized, double-blind, sham-controlled study with 254 healthy young participants.
• Transcranial direct current stimulation (tDCS) applied to left or right DLPFC during word encoding (perceptual, semantic, emotional).
• Free recall and recognition tasks assessed memory performance.

Main Results:

• Left DLPFC stimulation improved encoding and recall, particularly for semantically processed words.
• Enhancing left DLPFC activity increased memory for positive content and decreased memory for negative content.
• Right DLPFC stimulation enhanced memory formation for negative content.

Conclusions:

• The left DLPFC plays a significant role in assessing semantic properties during memory encoding, influencing episodic memory success.
• Hemispheric lateralization, with greater left DLPFC and reduced right DLPFC activity, biases memory trace formation towards positively valenced content.
• Differential modulation of DLPFC activity selectively impacts memory for semantic and emotional information.