Left tactile extinction following visual stimulation of a rubber hand

• Published in: Brain (London, England : 1878) England : 1878), 2000-11, Vol.123 (11), p.2350-2360
• Main Authors: Farnè, Alessandro, Pavani, Francesco, Meneghello, Francesca, Làdavas, Elisabetta
• Format: Article
• Language: English
• Subjects: Aged; Artificial Limbs - adverse effects; Biological and medical sciences; Brain Injuries - complications; Brain Injuries - pathology; Brain Injuries - physiopathology; Cerebral Cortex - pathology; Cerebral Cortex - physiopathology; cross-modal extinction; Extinction, Psychological - physiology; Female; Functional Laterality - physiology; Hallucinations - etiology; Hallucinations - pathology; Hallucinations - physiopathology; Humans; Male; Medical sciences; Middle Aged; multisensory integration; Neurology; Neuropsychological Tests; Perceptual Disorders - etiology; Perceptual Disorders - pathology; Perceptual Disorders - physiopathology; peripersonal space; Photic Stimulation - adverse effects; Physical Stimulation; Proprioception - physiology; Psychomotor Performance - physiology; RF = receptive field; rubber hand; Somatosensory Disorders - etiology; Somatosensory Disorders - pathology; Somatosensory Disorders - physiopathology; Space Perception - physiology; Vascular diseases and vascular malformations of the nervous system; VC = visually compatible; VI = visually incompatible
• ISSN: 0006-8950; 1460-2156
• DOI: 10.1093/brain/123.11.2350

In close analogy with neurophysiological findings in monkeys, neuropsychological studies have shown that the human brain constructs visual maps of space surrounding different body parts. In right-brain-damaged patients with tactile extinction, the existence of a visual peripersonal space centred on the hand has been demonstrated by showing that cross-modal visual–tactile extinction is segregated mainly in the space near the hand. That is, tactile stimuli on the contralesional hand are extinguished more consistently by visual stimuli presented near the ipsilesional hand than those presented far from it. Here, we report the first evidence in humans that this hand-centred visual peripersonal space can be coded in relation to a seen rubber replica of the hand, as if it were a real hand. In patients with left tactile extinction, a visual stimulus presented near a seen right rubber hand induced strong cross-modal visual–tactile extinction, similar to that obtained by presenting the same visual stimulus near the patient's right hand. Critically, this specific cross-modal effect was evident when subjects saw the rubber hand as having a plausible posture relative to their own body (i.e. when it was aligned with the subject's right shoulder). In contrast, cross-modal extinction was strongly reduced when the seen rubber hand was arranged in an implausible posture (i.e. misaligned with respect to the subject's right shoulder). We suggest that this phenomenon is due to the dominance of vision over proprioception: the system coding peripersonal space can be `deceived' by the vision of a fake hand, provided that its appearance looks plausible with respect to the subject's body.