A Common Neural Signal of Evidence Accumulation for Perceptual and Mnemonic Decisions

Abstract

Humans frequently make decisions based on sensory input from the external environment or information retrieved from memory. The centro-parietal positivity (CPP), an event-related EEG potential, has recently been identified as a neural correlate of sensory evidence accumulation during perceptual decision-making tasks. However, it remains unclear whether this component also reflects the accumulation of evidence in service of decisions grounded in semantic and episodic long-term memory. Across two experiments, we investigated whether the CPP serves as a domain-general neural signal of evidence accumulation. In Experiment 1, participants completed 2AFC perceptual and semantic memory tasks with varying levels of evidence strength. Perceptual judgements involved luminance discrimination of alphanumeric strings with three luminance difference levels controlling perceptual evidence strength. Semantic memory judgements involved discriminating population differences between U.S. states with census data used to define three bins of memory evidence strength. A CPP component was observed in both tasks whose build-up rate (i.e., slope) scaled with evidence strength, response time, and confidence in both stimulus-and response-locked analyses. Extending these findings to episodic memory, participants in Experiment 2 completed a two-alternative forced-choice word recognition task with target words varying in exposure frequency during learning to control episodic memory strength. Again, we found that CPP slopes scaled with memory strength, response time, and confidence. Together, these findings support the CPP as a domain-general neural signature of evidence accumulation across perceptual, semantic, and episodic mnemonic decisions.