Immersive bottle effect: Influence of virtual object simulation on modulation of corticospinal excitability by motor imagery

Motor imagery is a cognitive process that engages the motor system and facilitates motor learning, recovery, and performance. Its effectiveness relies on the activation of corticospinal pathways, which can be modulated by action observation. This study investigated whether observing graspable objects facilitates corticospinal excitability during motor imagery, and whether immersive virtual reality amplifies this effect. Twelve healthy adults of either sex completed a single session involving six conditions: rest, object observation on a screen or in virtual reality, motor imagery alone, and combined observation with motor imagery. Transcranial magnetic stimulation was used to record motor-evoked potentials from hand and forearm muscles, and fatigue and imagery quality were quantified. Results showed that observing a manipulable object during motor imagery significantly increased corticospinal excitability. This facilitation was strongest when the object was presented in a virtual environment. The effect was muscle-specific, targeting the agonist hand muscle of the imagined action (Abductor Pollicis Brevis), and was more pronounced at the higher stimulation intensity. Fatigue and imagery quality were similar across conditions. These findings indicate that object affordances can prime motor circuits and enhance motor imagery-induced neural activation, with immersive environments further reinforcing this effect. This is the first study demonstrating that combining motor imagery with virtual object observation maximizes corticospinal excitability. This approach may represent a promising tool for rehabilitation and sports training. Further studies should identify the optimal parameters and the neurophysiological markers of cortical modulation for this combination. NEW & NOTEWORTHYUsing transcranial magnetic stimulation with immersive virtual reality, we showed for the first time that observing a virtual object associated with the imagined movement increased corticospinal excitability to a greater extent than motor imagery performed alone.