# How sleeping minds decide: State-specific reconfigurations of lexical decision-making

## TL;DR

The study shows that the sleeping brain actively reconfigures decision-making strategies during different sleep stages, prioritizing meaningful information and adjusting for reduced efficiency.

## Contribution

The paper introduces state-specific computational mechanisms of lexical decision-making during sleep, using facial EMG and drift diffusion modeling.

## Key findings

- Lexical decisions during N1 sleep rely on enhanced sensory-motor processing and evidence accumulation for real words.
- Lucid REM sleep decisions depend solely on evidence accumulation with higher decision thresholds to maintain accuracy.
- Sleep involves dynamic reconfiguration of decision-making strategies rather than passive cognitive decline.

## Abstract

Sleep has traditionally been conceptualized as a state of cognitive disconnection, yet emerging evidence indicates that decision-making capacities persist across sleep stages. Here, we elucidate the computational mechanisms underlying real-time lexical decision-making during polysomnographically-verified sleep, using facial electromyography and hierarchical drift diffusion modeling in both healthy individuals and participants with narcolepsy. We found that lexical decision-making was preserved during N1 and lucid REM sleep, but relied on distinct computational strategies: in N1 sleep, both enhanced sensory-motor processing and increased evidence accumulation supported decisions about words, whereas in lucid REM sleep, lexical decisions were driven exclusively by evidence accumulation processes. Cross-state comparisons revealed two fundamental principles: (1) Selective preservation—during N1 sleep, lexical decisions for words were maintained while those for pseudowords were selectively impaired, indicating that cognitive resources during sleep are preferentially allocated to meaningful stimuli; (2) Parallel strategic adaptations—during lucid REM sleep, participants increased their decision thresholds, requiring more evidence before responding, which helped maintain accuracy even though the efficiency of evidence accumulation was reduced. Our findings demonstrate that, rather than a passive decline, sleep involves dynamic and state-specific reconfiguration of the computational mechanisms underlying decision-making, with important implications for understanding consciousness and cognitive flexibility.

Sleep is traditionally viewed as a state of cognitive disconnection, where the mind cannot interact with the world. We challenged this view by investigating how the sleeping brain makes decisions. We asked participants, including frequent lucid dreamers, to distinguish between real words and nonsense words while asleep, responding via subtle facial muscle movements. We found that the sleeping mind does not simply shut down; instead, it fundamentally changes how it processes information. During light sleep, participants retained the ability to respond quickly and accurately to familiar words but stopped responding to nonsense words, suggesting the brain prioritizes meaningful content. In lucid REM sleep—where dreamers are aware they are dreaming—behavior shifted differently: responses became much slower. Our mathematical modeling revealed that because the brain was less efficient at gathering information in this state, it adopted a “conservative” strategy, requiring more certainty before acting to maintain accuracy. These findings demonstrate that sleep is not a passive state, but a dynamic one where the brain actively reconfigures its decision-making strategies to suit the distinct states of consciousness.