Plasticity in the visual motion system of congenitally and late blind adults
Bedny, Konkle, Saxe, & Pascual-Leone
Absence of vision early in life leads to large-scale reorganization of visual brain regions in animals and blind humans. We studied the effects of blindness on two visual-motion perception regions: the middle temporal complex (MT+), which supports basic motion perception and the right superior temporal sulcus (rSTS), which supports biological motion perception.
Congenitally blind, late blind and sighted adults performed an auditory motion task, judging whether either footsteps or tones were approaching or receding (getting quieter or getting louder). In sighted individuals, MT+ was deactivated during auditory motion, whereas in congenitally blind adults, the MT+ complex responded to the motion of tones and footsteps. In a second auditory task, participants judged the semantic similarity of a pair of words, and the perceptual similarity of backward speech sounds. Neither the speech or backward-speech conditions activated MT+ in the congenitally blind, showing that MT+ responds selectively to auditory motion. Blind adults who lost their vision in adulthood did not show an auditory motion response in MT+, suggesting that there is a sensitive period for the recruitment of MT+ for auditory motion perception.
Like MT+, the rSTS responded more to sounds of footsteps than to the sound of moving tones. Unlike MT+, however, the rSTS of blind and sighted individuals was active above baseline in all auditory tasks. Further, the rSTS responded to linguistic sound and backwards speech in both sighted and blind individuals. The lowest response in the rSTS was to the moving tones condition. An intriguing possibility is that in blind individuals the rSTS responds not to auditory motion per se, but rather to socially relevant auditory stimuli.
Congenital blindness expands the processing of visual motion area MT+ to include auditory motion processing. The rSTS of congenitally blind participants was responsive to auditory biological motion and speech. Together these data suggest that higher order visual regions of blind individuals are reorganized to respond to similar domains of information in the auditory modality.
Bedny, M., Konkle, T., Saxe, R., & Pascual-Leone, A. Plasticity in the visual motion system of congenitally and late blind adults. Program No. 697.12. 2009 Neuroscience Meeting Planner. Chicago, IL: Society for Neuroscience, 2009. Online.