Transcranial magnetic stimulation of the visual cortex induces somatotopically organized qualia in blind subjects.
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.
Kupers
Ron
R
Department of Surgical Pathophysiology and Positron Emission Tomography Unit, Rigshosptitalet, DK-2100 Copenhagen, Denmark. ron@pet.rh.dk
Fumal
Arnaud
A
de Noordhout
Alain Maertens
AM
Gjedde
Albert
A
Schoenen
Jean
J
Ptito
Maurice
M
D000328:Adult; D001766:Blindness / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010292:Paresthesia / Q000139:chemically induced; D010719:Phosphenes / Q000502:physiology; D010775:Photic Stimulation; D010812:Physical Stimulation; D014059:Tongue / Q000502:physiology; D014110:Touch / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000502:physiology*