Relations between Visual Axis and Upper Extremity Motion during Eating in Healthy People: Correspondence of Eye Movement Pattern and Velocity Curve

Aim: Eye-hand coordination that occurs when an object gets closer to the body, as with eating motion, is unclear. we conducted a synchronization analysis of the visual axis and upper extremity motion using a spoon and chopsticks in healthy volunteers. The central aim of this study was to examine relations between the visual axis and upper extremity motion during eating. Methods: Participants were 12 healthy volunteers (4 men, 8 women) who were 20 - 49 years old. The participant carried the sponge cake from the plate to the mouth with a spoon or chopsticks. The upper extremity position at which the visual axis was removed from the food was designated as the critical visual point. The upper extremity motion velocity was chosen as an index. Results: The upper extremity motion show a bell-shaped velocity profile of the wrist during eating. When carrying the sponge cake from plate to mouth with a spoon, the visual axis remained on it after peak velocity. With chopsticks, the visual axis was kept on sponge cake for at least 0.19 s. Conclusion: Results show that visual guiding of upper extremity motion until the critical visual point is necessary for efficiency during eating. Additionally, this study speculate that the central nervous system extends a visual monitoring period in eating motion with a spoon compared to chopsticks and that it prevents dropping of food. This finding provides a basis for occupational therapists and physiotherapists to assist people who need guidance in eating motions