Respiratory phase alignment across memory encoding and retrieval improves task efficiency.

Increasing evidence indicates that respiratory rhythms are crucial for cognitive functions. Although recent findings have raised the possibility 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 monitoring nasal respiration. 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 phase-dependent respiratory effects, particularly the importance of respiratory phase alignment between encoding and retrieval. Notably, the late phase of exhalation during both encoding and retrieval may represent a favorable temporal window for enhancing memory task efficiency. These findings suggest that respiratory phase alignment modulates cognitive processes by providing an interoceptive, phase-dependent context for memory processing.