ABSTRACT
A major question in the field of sensory substitution concerns the nature of the perception generated by sensory substitution devices. In the present fMRI study, we investigated the neural substrates of pattern recognition through a device substituting audition for vision in blindfolded sighted subjects, before and after a short training period. Before training, pattern recognition recruited dorsal and ventral extra-striate areas. After training, the recruitment of these visual areas was found to have increased. These results suggest that visual imagery processes could be involved in pattern recognition and that perception through the substitution device could be visual-like.
Subject(s)
Auditory Perception/physiology , Brain Mapping , Cerebral Cortex/physiology , Discrimination Learning/physiology , Imagination/physiology , Pattern Recognition, Physiological/physiology , Adult , Humans , Magnetic Resonance Imaging , Male , Reference Values , Sensory Deprivation , Vision, OcularABSTRACT
We have previously shown that some visual motion areas can be specifically recruited by auditory motion processing in blindfolded sighted subjects [Poirier, C., Collignon, O., De Volder, A.G., Renier, L., Vanlierde, A., Tranduy, D., Scheiber, C., 2005. Specific activation of V5 brain area by auditory motion processing: an fMRI study. Brain Res. Cogn. Brain Res. 25, 650-658]. The present fMRI study investigated whether auditory motion processing may recruit the same brain areas in early blind subjects. The task consisted of simultaneously determining both the nature of a sound stimulus (pure tone or complex sound) and the presence or absence of its movement. When a movement was present, blind subjects had to identify its direction. Auditory motion processing, as compared to static sound processing, activated the brain network of auditory and visual motion processing classically observed in sighted subjects. Accordingly, brain areas previously considered as specific to visual motion processing could be specifically recruited in blind people by motion stimuli presented through the auditory modality. This indicates that the occipital cortex of blind people could be organized in a modular way, as in sighted people. The similarity of these results with those we previously observed in sighted subjects suggests that occipital recruitment in blind people could be mediated by the same anatomical connections as in sighted subjects.
Subject(s)
Blindness/physiopathology , Image Processing, Computer-Assisted , Imaging, Three-Dimensional , Magnetic Resonance Imaging , Motion Perception/physiology , Occipital Lobe/physiopathology , Recruitment, Neurophysiological/physiology , Sound Localization/physiology , Visual Perception/physiology , Adolescent , Adult , Aged , Blindness/congenital , Brain Mapping , Cerebral Cortex/physiopathology , Humans , Male , Middle Aged , Nerve Net/physiopathology , Orientation/physiology , Pitch Perception/physiologyABSTRACT
We tested the effects of using a prosthesis for substitution of vision with audition (PSVA) on sensitivity to the Ponzo illusion. The effects of visual experience on the susceptibility to this illusion were also assessed. In one experiment, both early-blind and blindfolded sighted volunteers used the PSVA to explore several variants of the Ponzo illusion as well as control stimuli. No effects of the illusion were observed. The results indicate that subjects focused their attention on the two central horizontal bars of the stimuli, without processing the contextual cues that convey perspective in the Ponzo figure. In a second experiment, we required subjects to use the PSVA to consider the two converging oblique lines of the stimuli before comparing the length of the two horizontal bars. Here we were able to observe susceptibility to the Ponzo illusion in the sighted group, but to a lesser extent than in a sighted non-PSVA control group. No clear effect of the ilusion was obtained in early-blind subjects. These results suggest that, at least in sighted subjects, perception obtained with the PSVA shares perceptual processes with vision. Visual experience appears mandatory for a Ponzo illusion to occur with the PSVA.
