Tool-Use Training Induces Changes of the Body Schema in the Limb Without Using Tool

Area of Science:

• Neuroscience
• Cognitive Psychology
• Human Motor Control

Background:

• Tool use is known to induce plasticity in the body schema, leading to a sense of the tool as an extension of the body.
• Previous research has not clarified if this 'tool embodiment' extends to limbs not directly interacting with the tool.
• The potential for inter-limb proprioceptive utilization in body schema expansion remains largely unexplored.

Purpose of the Study:

• To investigate whether tool embodiment can spread to a limb not directly using the tool.
• To determine if proprioceptive information from one limb can be utilized by another limb to modify the body schema.
• To examine the task-dependent nature of tactile perception changes following tool use.

Main Methods:

• Experiment 1: Blindfolded participants performed tactile distance perception tasks after using a cane for searching (Condition 1) or walking (Condition 2).
• Experiment 2: Controlled for potential confounding effects of posture differences (walking vs. standing) between conditions.
• Measurements focused on tactile distance perception on various body parts, including the forearm, hand, and calf.

Main Results:

• In Condition 1, tactile distance perception on the forearm increased, indicating body schema expansion.
• In Condition 2, tactile perception extended to the hand and forearm, and notably, to the non-tool-using calf.
• The influence of task (searching vs. walking) on directional tactile perception was observed.

Conclusions:

• Tool embodiment can extend to body parts not directly involved in tool use, demonstrating cross-limb body schema plasticity.
• Proprioceptive information from one limb can be leveraged by another, expanding the perceived body space.
• These findings highlight the dynamic and adaptable nature of the human body schema.