Illusory and veridical mapping of tactile objects in the primary somatosensory and posterior parietal cortex.

Abstract

While several behavioral and neuroscience studies have explored visual, auditory, and cross-modal illusions, information about the phenomenology and neural correlates of somatosensory illusions is meager. By combining psychophysics and somatosensory evoked potentials, we explored in healthy humans the neural correlates of 2 compelling tactuo-proprioceptive illusions, namely Aristotle (1 object touching the contact area between 2 crossed fingers is perceived as 2 lateral objects) and Reverse illusions (2 lateral objects are perceived as 1 between crossed-fingers object). These illusions likely occur because of the tactuo-proprioceptive conflict induced by fingers being crossed in a non-natural posture. We found that different regions in the somatosensory stream exhibit different proneness to the illusions. Early electroencephalographic somatosensory activity (at 20 ms) originating in the primary somatosensory cortex (S1) reflects the phenomenal rather than the physical properties of the stimuli. Notably, later activity (around 200 ms) originating in the posterior parietal cortex is higher when subjects resist the illusions. Thus, while S1 activity is related to illusory perception, PPC acts as a conflict resolver that recodes tactile events from somatotopic to spatiotopic frames of reference and ultimately enables veridical perception.

• Authors: Ilaria Bufalari, Francesco Di Russo, Salvatore Maria Aglioti
• Journal: Cerebral cortex (New York, N.Y. : 1991) (Cereb Cortex) Vol. 24 Issue 7 Pg. 1867-78 (Jul 2014) ISSN: 1460-2199 [Electronic] United States
• PMID: 23438449 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: [email protected].

Topics

• Adult
• Analysis of Variance
• Brain Mapping
• Electroencephalography
• Evoked Potentials, Somatosensory (physiology)
• Female
• Humans
• Illusions (physiology)
• Male
• Parietal Lobe (physiology)
• Physical Stimulation
• Psychophysics
• Reaction Time (physiology)
• Statistics as Topic
• Touch (physiology)
• Young Adult