Transcranial Direct Current Stimulation over the Prefrontal Cortex Alters Encoding and Judgments of Learning Based on...

Area of Science:

• Cognitive Neuroscience
• Metamemory Research
• Neuroscience of Memory

Background:

• Judgments of learning (JOLs) are subjective confidence assessments of future recall.
• JOLs often rely on processing fluency, leading to inaccuracies when disfluent items are better remembered.
• The dorsolateral prefrontal cortex (DLPFC) and anterior prefrontal cortex (aPFC) are implicated in JOLs and memory encoding.

Purpose of the Study:

• To investigate the causal roles of the DLPFC and aPFC in encoding, JOLs, and JOL accuracy.
• To determine how the functions of DLPFC and aPFC in JOLs vary based on the underlying encoding information (fluency).

Main Methods:

• Used high-definition transcranial direct current stimulation (HD-tDCS) to modulate DLPFC and aPFC activity.
• Participants studied words varying in fluency (frequency, orientation) and made JOLs.
• Assessed encoding success via recognition memory and analyzed JOL accuracy.

Main Results:

• DLPFC stimulation impaired encoding, increasing false alarms.
• aPFC stimulation improved JOL accuracy for disfluently encoded (low-frequency) words.
• Both DLPFC and aPFC stimulation decreased JOL accuracy for fluently encoded (high-frequency) words.

Conclusions:

• The roles of DLPFC and aPFC in metamemory accuracy are dependent on the basis of the JOL (e.g., fluency).
• HD-tDCS can causally dissociate the contributions of prefrontal regions to memory and metamemory.
• Findings advance understanding of prefrontal cortex involvement in subjective memory assessment and accuracy.