1. Activation of the primary visual cortex by Braille reading in blind subjects Norihiro Sadato, Alvaro Pascual-Leone, Jordan Grafman, Vincente Ibanez, Marie-Pierre Deiber, George Dold, & Mark Hallett Parmvir Boparai

2. Introduction Sensory info. of primary visual cortex comes from lateral geniculate Sensory info. of primary visual cortex comes from lateral geniculate But generally not known to obtain input from other sensory modalities But generally not known to obtain input from other sensory modalities Does p.v.c. receive input from somatosensory system in blind people? Does p.v.c. receive input from somatosensory system in blind people? E.g. Blind people read Braille E.g. Blind people read Braille

3. Experimental Tasks 8 blind and 10 sighted subjects were hooked up to a PET scanner (and posterior brain region examined) Reading Task: Word and non-word tasks 8 characters of Braille letters (per 2.4 seconds) presented and subject was to identify if strings of letters were words or non-words............................................

4. Experimental Tasks Somatosensory Tasks: Somatosensory Tasks: Character Task: Character Task: 30 sets of upper case Braille letters presented 30 sets of upper case Braille letters presented Subjects asked to identify which sets had identical letters (3 out of 30 sets were actually identical) Subjects asked to identify which sets had identical letters (3 out of 30 sets were actually identical) Width Task: Width Task: 2 grooves cut into paper covered with Braille 2 grooves cut into paper covered with Braille Subjects asked to identify which grooves had same width (grooves either 3.2mm or 4.6mm) Subjects asked to identify which grooves had same width (grooves either 3.2mm or 4.6mm)

5. Results Reading Task: Reading Task: Activation of Medial occipital lobe  Brodmann Area 17 (p.v.c.)  bilaterally extending to extrastriate cortexes (in blind subjects) Activation of Medial occipital lobe  Brodmann Area 17 (p.v.c.)  bilaterally extending to extrastriate cortexes (in blind subjects) Increased blood flow in primary visual cortex Increased blood flow in primary visual cortex

6. Results Somatosensory Tasks: Somatosensory Tasks: Activation in primary visual cortex also (in blind subjects only) Activation in primary visual cortex also (in blind subjects only) Increased blood flow in p.v.c, but less than when reading (blind subjects). Increased blood flow in p.v.c, but less than when reading (blind subjects). Sighted subjects = decreased blood flow in p.v.c. Sighted subjects = decreased blood flow in p.v.c.

7. Discussion Results suggest that somatosensory info. input does facilitate activation of V.C. in blind people. Results suggest that somatosensory info. input does facilitate activation of V.C. in blind people. Selective attention to a modality functions differently in sighted than blind. Selective attention to a modality functions differently in sighted than blind. Most subjects congenitally blind or at early age. This rules out visual imagery as an explanation. Most subjects congenitally blind or at early age. This rules out visual imagery as an explanation.

8. Discussion Theory: Theory: More neuronal connections (axonal sprouting) form after deprivation of a certain modality. More neuronal connections (axonal sprouting) form after deprivation of a certain modality. Study showed that monkey that was visually deprived early had growth of neurons project from visual association cortex and parietal cortex to primary visual cortex. Study showed that monkey that was visually deprived early had growth of neurons project from visual association cortex and parietal cortex to primary visual cortex. Suggests that somatosensory input can travel though visual association cortex to p.v.c. in the blind subjects. Suggests that somatosensory input can travel though visual association cortex to p.v.c. in the blind subjects.

9. Strength: Strength: Provides reassuring evidence for the activation of the visual cortex in blind individuals Provides reassuring evidence for the activation of the visual cortex in blind individuals Weakness: Weakness: Since this wasn’t a longitudinal study, unable to monitor whether axonal sprouting had occurred in theses individuals. Thus no concrete evidence for theory Since this wasn’t a longitudinal study, unable to monitor whether axonal sprouting had occurred in theses individuals. Thus no concrete evidence for theory Follow Up: Follow Up: Testing people who have not be congenitally blind or at a early age. Is visual cortex activated? If so how? Same mechanism as these subjects or visual imagery? Testing people who have not be congenitally blind or at a early age. Is visual cortex activated? If so how? Same mechanism as these subjects or visual imagery?

10. Source: Source: Sadato et al., 1996. Activation of the primary visual cortex by Braille reading in blind subjects. Nature 380(6574): 526-8. Daredevil Daredevil http://www.youtube.com/watch?v=X2x2tb daa5c http://www.youtube.com/watch?v=X2x2tb daa5c The End