Age-related differences in embodying a tool under visual deprivation

Tool embodiment enables external objects to be integrated into the body model during action. While visual input is thought to play a major role in this process, it remains unclear how short-term visual deprivation affects ownership and agency over tools, particularly across the adult lifespan. This study examined whether blindfolded tool-use training with a cane elicits subjective ownership and agency in younger and older adults and whether these experiences relate to plasticity in body schema (BS) and peripersonal space (PPS). Forty-three adults (younger and older groups) completed two conditions: A) blindfolded object search with the cane and B) blindfolded navigation using the cane. BS changes were assessed via tactile distance judgments, and PPS changes via reaching distance estimation. Participants rated ownership and agency following each condition. Across age groups and conditions, ownership ratings remained below established embodiment thresholds, whereas agency ratings were consistently above threshold, indicating preserved action-based tool control despite the absence of vision. Regression analyses revealed that increased PPS and BS plasticity predicted greater agency, particularly during navigation, but this coupling was significantly stronger in younger adults. Ownership did not show reliable associations with either measure of plasticity. These findings demonstrate that tool-related agency remains flexible under visual deprivation, though with reduced sensorimotor-agency coupling in older adults. By contrast, body ownership appears resistant to short-term recalibration without vision. This dissociation highlights age-dependent mechanisms supporting tool embodiment and emphasizes the critical role of multisensory prediction in sustaining agency over tools across the lifespan.