Breath as an internal context: Respiratory phase alignment between encoding and retrieval optimizes memory performance.

Increasing evidence suggests that respiratory rhythms are crucial for cognitive functions. Although recent findings suggest that respiratory activity may serve as an internal contextual framework during memory processes, the contribution of specific respiratory phases to encoding and retrieval remains unclear. Here, we investigated the breathing-dependent performance of 30 healthy volunteers during a visual delayed matching-to-sample recognition memory task while their nasal respiration was monitored. Reaction times (RTs) decreased when visual cues were both encoded and retrieved during the late phase of exhalation. In contrast, longer RTs were observed during late exhalation at retrieval when encoding occurred either (i) during a period that encompassed inspiratory onset (i.e., exhalation-to-inhalation transition or EI transition) or (ii) during the early phase of inhalation. These contrasting outcomes under identical retrieval conditions highlight the phase-dependent effects of respiration, specifically the alignment of respiratory timing between encoding and retrieval. Importantly, we found that the late phase of exhalation during both encoding and retrieval may represent a favorable temporal window for shaping memory performance. These findings suggest that respiratory phase alignment modulates memory processes by providing an interoceptive, phase-dependent context for cognition.