Sadato et al. (1996)

From Psy3241

Activation of the Primary Visual Cortex by Braille Reading in Blind Subjects

Presentation by: Amanda Terr and Jeff Mueller

This article is about plasticity in the primary visual cortex. This area of the brain is known to receive input from the eyes but not from any other senses. However, researchers wanted to see if this was the case in all people. Twenty six participants were used in this study: 8 are blind Braille readers, 8 are blind non- Braille readers and 10 sighted controls. During the experiment, the Braille readers were presented with 8 character, non-contracted Braille-letter strings every 2.4 second. The first condition, the "word" condition, 41 words and 3 non words were presented. In the other condition, the "non word" condition, 41 non words and 3 words were presented. Participants were instructed to respond by saying "num" when they encountered words. The other participants were given four non Braille tactile tasks. The first was the sweep task, in which the participants swept their index fingers over a rough surface covered in Braille dots. In the other three tasks the participants were asked to discriminate Braille based on angles, width and character.

The Braille reading by the Braille reading participants activated the medial occipital lobe. The 3 non Braille discrimination tasks also activated the primary visual cortex in the blind participants but with a smaller increase of regional cerebral blood flow (rcbf) than in the Braille reading. In the sighted subjects, the tasks elicited a decrease in rcbf. The non discrimination task did not activate the primary visual cortex in the sighted or blind individuals. This suggests that selective attention does not affect the primary visual cortex the same way in blind and sighted subjects. The findings also suggest that somatosensory input could be transferred to the primary visual cortex through visual association areas during Braille reading by blind subjects.