Selective Modulation of Evidence Accumulation by Hippocampal Theta Oscillations During Mnemonic Decision-Making

Area of Science:

• Neuroscience
• Cognitive Science
• Memory Research

Background:

• Episodic memory relies on pattern separation to differentiate similar experiences.
• The hippocampus, including dentate gyrus, CA3, and CA1, is crucial for memory, but its temporal dynamics in decision-making are unclear.

Purpose of the Study:

• To investigate the relationship between hippocampal theta oscillations and evidence accumulation during mnemonic discrimination.
• To explore how these neural dynamics influence memory-based decisions.

Main Methods:

• Source-localized magnetoencephalography (MEG) and computational modeling (Linear Ballistic Accumulator model).
• Participants performed the Mnemonic Similarity Task, classifying images as "Old," "Similar," or "New."
• Hippocampal theta power was analyzed in relation to trial-by-trial drift rates (evidence accumulation).

Main Results:

• Hippocampal theta power predicted evidence accumulation dynamics during mnemonic discrimination.
• Left hippocampal theta negatively correlated with drift toward "New" responses on lure trials.
• Right hippocampal theta positively correlated with drift toward "Similar" responses on foil trials, indicating partial-match sensitivity.

Conclusions:

• Hippocampal theta oscillations selectively index partial-match sensitivity in memory.
• These neural fluctuations are linked to the dynamics of memory-guided decision-making.
• The study demonstrates the feasibility of integrating deep-source MEG with computational models for studying memory.