title: 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: Dipartimento di Psicologia, Università degli Studi di Roma "La Sapienza", I-00185 Rome, Italy, Laboratorio di Neuroscienze Sociali.
authors: Ilaria
authors: I
authors: Bufalari
authors: Centro Ricerche Neuropsicologia, IRCCS Fondazione Santa Lucia, I-00179 Rome, Italy and Dipartimento di Scienze Motorie, Umane e della Salute, Università degli Studi di Roma "Foro Italico", I-00135 Rome, Italy.
authors: Francesco
authors: F
authors: Di Russo
authors: Dipartimento di Psicologia, Università degli Studi di Roma "La Sapienza", I-00185 Rome, Italy, Laboratorio di Neuroscienze Sociali.
authors: Salvatore Maria
authors: SM
authors: Aglioti
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008297:Male; D010296:Parietal Lobe / Q000502:physiology*; D010812:Physical Stimulation; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology; D013223:Statistics as Topic; D014110:Touch / Q000502:physiology*; D055815:Young Adult
keywords: Aristotle illusion; posterior parietal cortex; primary somatosensory cortex; somatosensory evoked potentials; spatial remapping of touch