Sensory substitution devices (SSDs) transform visual information into auditory or tactile input non-invasively, and enable the blind to “see� using their other senses. Recent studies have shown that shape recognition using the vOICe, a visual-to-auditory SSD, activates the lateral occipital cortex (LOC), the visual object related area, after prolonged use of the device (i.e. following weeks of training). One remaining question is whether such plastic changes in brain areas (especially visual areas) can occur much more rapidly? Occipital cortex undergoes dramatic cross-modal plasticity in the blind. This could reflect connectivity and processing, which exist also in sighted (but are inhibited to some extent by visual input), or massive reorganization and growth of new connections due to prolonged blindness. Here we studied neuroplasticity in time scales that do not enable growth of new connections. Using fMRI, we studied blind and sighted individuals to define the neural correlates, brain dynamics and brain plasticity of learning to use the vOICe SSD. Naïve subjects were scanned during a SSD object recognition task before they were given an explanation of the visual-to-auditory transformation algorithm, and then, at the same day, following a one-hour training session in which the vOICe principles were explained and practiced. Following a one-hour shape-recognition training session, activation of the LOC increased significantly, in both sighted and congenitally blind subjects. These results show that very short training of the use of SSDs results in a task-specific rapid effect of neuroplasticity in the object related visual cortex. These results suggest that visual cortex plasticity can be seen in extremely short time scales, in both sighted and blind individuals, giving high hopes for the possibility of quick learning and useful implementation of sensory substitution in the blind. More importantly, the speed of these functional changes makes the establishment of new connections highly improbable. Thus, the rapid changes in existing connectivity might be an important mechanism for such rapid neuroplasticity in the adult brain.