The brain dynamics of congenitally blind people seeing faces with sound
Sensory substitution devices (SSDs) convert images to sounds to equip blind individuals with nominally visual functions, like face or letter sensitivity. Prior studies showed that image-to-sound SSDs engage cortices ordinarily specialised for visual functions. However, the brain dynamics of SSD-supported perception remains unknown. Either visual cortices are the first locus of discrimination of SSD percepts, or their activation is a by-product of perceptual processes unfurling elsewhere, such as in auditory cortices. Resolving this uncertainty is critical for understanding whether the blind truly "see" via SSDs. Using electrical neuroimaging of EEG data from congenitally blind adults, we show for the first time that inferotemporal visual cortices are the earliest site of face sensitivity when conveyed via SSDs. The blind do indeed "see" with SSDs. By providing the temporal dynamics of SSD perception, our findings provide unique evidence for the theory that cortices are characterised by task-contingent functional organisation.