Transcranial Magnetic Stimulation of the Visual Cortex Induces Somatotopically Organized Qualia in Blind Subjects

• Published in: Proceedings of the National Academy of Sciences - PNAS 2006-08, Vol.103 (35), p.13256-13260
• Main Authors: Kupers, Ron, Fumal, Arnaud, de Noordhout, Alain Maertens, Gjedde, Albert, Schoenen, Jean, Ptito, Maurice
• Format: Article
• Language: English
• Subjects: Adult; Behavioral neuroscience; Biological Sciences; Blindness; Blindness - physiopathology; Braille; Brain research; cross-modal plasticity; Female; Human health sciences; Humans; Male; Middle Aged; Neurologie; Neurology; Neurosciences & behavior; Neurosciences & comportement; Paresthesia - chemically induced; Phosphenes; Phosphenes - physiology; Photic Stimulation; Physical Stimulation; Physiological stimulation; Positron emission tomography; rewiring; Sciences de la santé humaine; Sciences sociales & comportementales, psychologie; sensation; Sense of touch; Sensory perception; Social & behavioral sciences, psychology; Tongue; Tongue - physiology; Touch - physiology; Transcranial Magnetic Stimulation; vision; Visual cortex; Visual Cortex - physiology; Visual perception; Visually impaired persons
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.0602925103

After loss of a particular sensory channel, the deprived cortex can be activated by inputs from other sensory modalities. It is not known whether activation of the rewired cortex evokes subjective experiences characteristic of that cortex or consistent with the rerouted sensory information. In a previous study, blind subjects were trained to perform visual tasks with a tongue display unit, a sensory substitution device that translates visual displays into electrotactile tongue stimulation. This cross-modal sensory stimulation activated their visual cortices. We now extend this finding by using transcranial magnetic stimulation to examine the perceptual correlates of training-induced plastic responses. We find that blind subjects proficient with the use of the tongue display unit report somatopically organized tactile sensations that are referred to the tongue when transcranial magnetic stimulation is applied over the occipital cortex. No such sensations were evoked in trained, blindfolded, seeing control subjects who performed the sensory substitution task equally well. These data show that the perceptual correlate of activity in a given cortical area reflects the characteristics of its novel sensory input source.