Olfactory Cues to Reduce Retrograde Interference During the Simultaneous Learning of Conflicting Motor Tasks

Abstract

We investigated the ability of humans to adapt to a novel environment by kinematic transformation. This adaptation was studied via behavioural experiments using a robotic manipulandum – a system designed to arbitrarily generate virtual force fields against a human hand and subsequently record the hand’s trajectory. By repeating motor tasks, this study’s participants gradually learned to move correctly under a newly experienced force field, such as rotating in a clockwise direction. However, each participant’s motor memory was destroyed if he/she experienced an opposing force field (e.g., in a counterclockwise direction) immediately after learning the initial movement, which is known as retrograde interference. In some previous studies, it has been considered that by presenting sensory cues to highlight the difference in two opposing force fields, participants can learn both force fields independently without interference. In this study, we investigated the functionality of olfactory cues – specifically lemon and lavender odors – in reducing retrograde interference. Forty-five university students participated in an experiment using a robotic manipulandum. Our results have shown that the presence of lemon odor reduces the destruction of motor memory, while that of lavender did not, suggesting that odors can enhance simultaneous motor learning but the effect depends on the type of odor used.