Body and spatial representational plasticity during training with and without cane in blindfolded young adults and older adults

Prior research showed that active tool use extends the body representation of both the forearm and hand wielding the tool and the calf, even without direct tool-environment interaction, particularly under blindfolded conditions (short-term visual deprivation) in young adults. In this research, we examined whether changes in body schema (BS) in the absence of vision induced by active tool-use training are limb-specific in young and older adults. Additionally, we examined whether plasticity of peripersonal space (PPS) predicts such effects. A total of 43 healthy young and older adults underwent three conditions of tool-use training: (Condition A) while blindfolded, using a cane to find a target object with no time restriction; (Condition B) walking blindfolded with a cane for 20 minutes; (Condition C) walking blindfolded without a cane for 20 minutes. Older adults had 10 minutes of training in conditions B and C. Changes in the BS were assessed using a tactile distance judgment task (TDJ), where participants judged distances between two tactile stimuli applied to their right forearm, hand, shin, and foot in a proximodistal orientation. PPS was assessed using a reaching distance estimation task (RDE). Findings suggest that while tool-use and task-specific conditions influence BS, their effects may be more localized and context-dependent than broadly systematic. Therefore, results of this study call into question to what degree and how robustly BS is plastic and limb specific in the absence of vision and how malleable this is by extension of the PPS toward the acting space by tool-use training in healthy aging. Keyword: Tool-use, young adults, old adults, vision, blindfolded, body schema, peripersonal space