Cross-modal integration and plastic changes revealed by lip movement, random-dot motion and sign languages in the hearing and deaf.
Sign language activates the auditory cortex of deaf subjects, which is evidence of cross-modal plasticity. Lip-reading (visual phonetics), which involves audio-visual integration, activates the auditory cortex of hearing subjects. To test whether audio-visual cross-modal plasticity occurs within areas involved in cross-modal integration, we used functional MRI to study seven prelingual deaf signers, 10 hearing non-signers and nine hearing signers. The visually presented tasks included mouth-movement matching, random-dot motion matching and sign-related motion matching. The mouth-movement tasks included conditions with or without visual phonetics, and the difference between these was used to measure the lip-reading effects. During the mouth-movement matching tasks, the deaf subjects showed more prominent activation of the left planum temporale (PT) than the hearing subjects. During dot-motion matching, the deaf showed greater activation in the right PT. Sign-related motion, with or without a lexical component, activated the left PT in the deaf signers more than in the hearing signers. These areas showed lip-reading effects in hearing subjects. These findings suggest that cross-modal plasticity is induced by auditory deprivation independent of the lexical processes or visual phonetics, and this plasticity is mediated in part by the neural substrates of audio-visual cross-modal integration.
Sadato
Norihiro
N
National Institute for Physiological Sciences, Okazaki, Japan. sadato@nips.ac.jp
Okada
Tomohisa
T
Honda
Manabu
M
Matsuki
Ken-Ichi
K
Yoshida
Masaki
M
Kashikura
Ken-Ichi
K
Takei
Wataru
W
Sato
Tetsuhiro
T
Kochiyama
Takanori
T
Yonekura
Yoshiharu
Y
D000328:Adult; D003638:Deafness / Q000503:physiopathology*; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D006801:Humans; D008085:Lipreading; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D012813:Sign Language