Distinct neural signatures of multimodal resizing illusions

Area of Science:

• Neuroscience
• Cognitive Psychology
• Psychophysics

Background:

• Illusory body resizing often relies on multisensory integration.
• Previous research links multisensory illusions to frontal theta and parietal gamma oscillations.
• Emerging evidence suggests unimodal visual stimuli can also induce embodiment illusions.

Purpose of the Study:

• Investigate neural differences between multisensory visuo-tactile and unimodal visual resizing illusions.
• Understand the neural underpinnings of resizing illusions in healthy individuals using electroencephalography (EEG).
• Hypothesize stronger illusions in multisensory vs. unimodal conditions and specific oscillatory activity patterns.

Main Methods:

• Preregistered study with 48 healthy participants.
• Utilized electroencephalography (EEG) to record brain activity.
• Compared subjective and neural responses across multisensory, unimodal visual, and incongruent conditions.

Main Results:

• Multisensory illusions were stronger than unimodal visual illusions, partially supporting Hypothesis 1.
• Increased parietal gamma activity was observed in multisensory vs. unimodal conditions, occurring later than in rubber hand illusions.
• Increased parietal theta activity was found in incongruent vs. non-illusion conditions.
• Only 27% experienced unimodal visual illusions, compared to 73% for multisensory illusions.

Conclusions:

• Multisensory integration plays a crucial role in illusory body size perception.
• The temporal dynamics of neural integration in resizing illusions differ from those in rubber hand illusions.
• Distinct neural signatures may underlie the experience of visual-only resizing illusions.