Impact of Early Deafness and Early Exposure to Sign Language on the Cerebral Organization for Motion Processing

Abstract

This functional magnetic resonance imaging study investigated the impact of early auditory deprivation and/or use of a visuospatial language [American sign language (ASL)] on the organization of neural systems important in visual motion processing by comparing hearing controls with deaf and hearing native signers. Participants monitored moving flowfields under different conditions of spatial and featural attention. Recruitment of the motion-selective area MT-MST in hearing controls was observed to be greater when attention was directed centrally and when the task was to detect motion features, confirming previous reports that the motion network is selectively modulated by different aspects of attention. More importantly, we observed marked differences in the recruitment of motion-related areas as a function of early experience. First, the lateralization of MT-MST was found to shift toward the left hemisphere in early signers, suggesting that early exposure to ASL leads to a greater reliance on the left MT-MST. Second, whereas the two hearing populations displayed more MT-MST activation under central than peripheral attention, the opposite pattern was observed in deaf signers, indicating enhanced recruitment of MT-MST during peripheral attention after early deafness. Third, deaf signers, but neither of the hearing populations, displayed increased activation of the posterior parietal cortex, supporting the view that parietal functions are modified after early auditory deprivation. Finally, only in deaf signers did attention to motion result in enhanced recruitment of the posterior superior temporal sulcus, establishing for the first time in humans that this polymodal area is modified after early sensory deprivation. Together these results highlight the functional and regional specificity of neuroplasticity in humans.

Neural correlates of human action observation in hearing and deaf subjects

“…These data are consistent with observations that, despite auditory deprivation, deaf signers show activity within classical auditory regions in response to visual linguistic stimuli (Petitto et al, 2000;Bavelier et al, 2001;Emmorey et al, 2002;MacSweeney et al, 2002;Fine et al, 2005). Brain imaging studies of signers have reported robust right hemisphere perisylvian activation for signing Bavelier et al, 2001;MacSweeney et al, 2004;Newman et al, 2002). The present data, which uses individual sign stimuli, show little evidence of right perisylvian activation when contrasted against our baseline task ( Figure 3c, Table 1c, right panel) and in the direct contrast to non-linguistic gestures ( Figure 5, Table 5, left panel).…”

Dissociating cognitive and sensory neural plasticity in human superior temporal cortex

“…Even in a case in which the auditory cortex of DS is more responsive to any visual stimulation, this effect could be driven by a top-down mechanism developed with language experience. Another strategy has been to use hearing native signers (hearing children of deaf parents) as controls 8,[13][14][15] . With that comparison it is difficult to be conclusive about whether an effect arises from deafness or from different language experience.…”

Visualizando a elaboração da linguagem em surdos bilíngues por meio da ressonância magnética funcional

“…Nesse âmbito, Bavelier et al (2001) referiram que a condição desses ouvintes bilíngues bimodais é consequência da aquisição simultânea de duas línguas: a de sinais, pelas interações linguísticas entre os familiares, e a oral, pela convivência com a comunidade ouvinte. , Emmorey e McCullough (2009) e MacSweeney et al (2002b) sugeriram que tal condição possa interferir na organização cerebral das línguas.…”