The average training duration of participants here was 73 hr, with up to 10 hr devoted to learning to read using the SSD. As part of the training program, the participants were taught (using verbal explanations and palpable images; see Figure 1D

and Supplemental Experimental Procedures) how to process 2D still (static) images, including hundreds of images of seven structured categories: geometric shapes, Hebrew letters and digital numbers, body postures, everyday objects, textures (sometimes with geometric shapes placed over visual texture, used to teach object-background segregation), www.selleckchem.com/products/z-vad-fmk.html faces, and houses (see Figure 1E; see Movie S1 for a demo of the visual stimuli and their soundscape representations). For full details on the training technique and protocol, see the Supplemental Experimental Procedures.

After the structured training, participants could tell upon hearing a soundscape which category it represented. This required Gestalt object perception and generalization of the category principles and shape perception to novel stimuli. They could also determine multiple features of the stimulus, enabling them to differentiate between objects within categories. For an example, see Movie S2, depicting one congenitally blind check details participant reading a three-letter word and another participant recognizing emotional facial expressions. In order to assess the efficiency of training in terms of visual recognition, six of the participants in the training protocol underwent a psychophysical evaluation of their Ketanserin ability to identify different object categories. They were required to categorize 35 visual images (in pseudorandomized order) as belonging to the seven object categories.

Each stimulus was displayed using headphones for four repetitions (totaling 8 s), followed by a verbal response. The average rate of object classification success in the blind was 78.1% (±8.8% SD), significantly better than chance (14%; see Figure 1F, t test p < 0.00005). Letter category recognition did not differ from that of the other object categories (all p > 0.05, corrected for multiple comparisons). In order to minimize sensory-motor artifacts, no recording of performance was conducted during the fMRI scan. Prior to each scan, we verified that the subjects were able to easily recognize learned stimuli from the tested categories (see more detail in Supplemental Experimental Procedures). The main study included six experimental conditions presented in a block design paradigm. Each condition included ten novel soundscapes representing unfamiliar images from the trained object categories: letters, faces, houses, body shapes, everyday objects, and textures. Each condition was repeated five times, in a pseudorandom order. In each epoch, three different stimuli of the same category were displayed, each for 4 s (two repetitions of a 2 s stimulus). For instance, in each letter epoch, the subject was presented with a novel meaningless three-consonant letter string.