Distinct FN400/N400 memory effects for perceptually fluent and disfluent words

Area of Science:

• Cognitive Neuroscience
• Psychology
• Neuroscience

Background:

• Recognition memory is often linked to perceptual fluency, where easier processing leads to more "old" responses.
• The precise neural underpinnings of how perceptual fluency affects familiarity and recognition judgments are not fully understood.
• Event-related potentials (ERPs) offer a way to investigate the temporal dynamics of neural processes during recognition.

Purpose of the Study:

• To investigate the neural mechanisms underlying the effect of perceptual fluency on recognition memory using ERPs.
• To examine how manipulating word clarity (fluency) influences behavioral responses and ERP components during recognition.
• To explore whether distinct neural pathways support familiarity-based recognition under varying levels of perceptual fluency.

Main Methods:

• Two ERP experiments were conducted where participants encoded words and later performed a recognition test.
• Perceptual fluency was manipulated by presenting test words at either clear or blurry visual clarity levels.
• Behavioral recognition data (hits, false alarms) and ERPs (N400, Late Positive Component - LPC, Frontal N400 - FN400) were recorded and analyzed.

Main Results:

• In a more demanding task (Experiment 1), blurry words led to more hits, larger N400 and LPC old/new effects, and a frontal FN400 for high-confidence responses.
• In a less demanding task (Experiment 2), no behavioral differences were found, but ERPs showed a frontal FN400 for blurry words and a parietal N400 for clear words.
• Early ERP effects related to perceptual fluency were observed in both experiments, indicating immediate processing differences.

Conclusions:

• Perceptual fluency can enhance both semantic processing and familiarity, contributing to recognition judgments.
• The neural pathways supporting familiarity-based recognition may differ depending on the level of perceptual fluency (e.g., clear vs. blurry words).
• ERP findings suggest that the interpretation of fluency influences the engagement of distinct neural mechanisms in recognition memory.