“Observing S.B. in his daily life is a surprising experience since one is confronted by a person who alternately seems blind or visually normal depending on the behaviour required.”

Lê et al., 2002

S.B. is 32 years old male who has been extensively studied by researchers in the field of vision and perception. At the age of 3, S.B. developed meninogeoncephalitis which resulted in damage to several sections of his brain. The cerebral damage affected both the right and left ventral streams and the right dorsal stream of S.B.’s visual system. This left S.B with a visual condition similar to visual agnosia, where visual information is only processed through the dorsal stream.

S.B went to school for the partially visually impaired between the ages of 6 and 16. Even though S.B. was unable to perceive textual objects, read words, recognise faces or shapes, and perceive colour, many of his teachers were unable to believe that he was blind due to his ability to move though different environments and react to moving objects. Currently, S.B.’s visual system is still limited, however, he is able move through space without difficulty, ride a motorcycle, participate in sports such as goalkeeping, swimming and ping-pong, and throw catch and juggle two table tennis balls at the same time.

S.B.’s visual capabilities have been limited to what is possible when only the dorsal stream is in use. S.B. has the capability to perform basic ‘where’ processing but when asked to visually identify objects he was unable to do so. The abilities and limitations exhibited by S.B. are similar to those experienced by people afflicted with visual agnosia. However, researchers who studied S.B. were hesitant to label S.B. as having visual agnosia. The medical definition of visual agnosia implies that at some point in time the subject lost the ability to see with the ventral stream. S.B.’s situation is different in that he lost the use of his ventral stream at a young age. As a result, studying S.B. has demonstrated how the visual brain develops without the ventral stream.

Background information about S.B. was taken from Lê et al., 2000.

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