Search Abstracts | Symposia | Slide Sessions | Poster Sessions
EBA–Language Network Connectivity in Deaf Signers vs. Hearing Nonsigners
Poster Session D, Thursday, October 1, 4:30 - 6:30 pm, Wangari Maathai
Stephen McCullough1, Sarah Kimbley1, Karen Emmorey1; 1SDSU
The extrastriate body area (EBA) in the lateral occipitotemporal cortex is known to be associated with visual perception of the human body and body parts. Since sign language relies entirely on the visual-manual modality, we hypothesized that the EBA may exhibit greater connectivity with the core language network in signers. A previous study found that motion-related meanings in American Sign Language (ASL) sentences elicited top-down semantic modulation of activity in MT+ (McCullough et al., 2012), revealing the possibility of robust functional connectivity between the core language network and visual processing regions for signers. To test the hypothesis that the connectivity between the EBA and the language network is stronger for signers, we examined whole-brain seed-to-voxel functional connectivity (FC) from the EBA in deaf early signers (n = 14) and hearing non-signers (n=14). Participants performed a rapid 1-back (repetition detection) task while viewing rapidly presented static hands, static poses, and cars (object control). We conducted task-modulated FC analyses (voxel p < .001 uncorrected, cluster p-FDR ≤ .05) using the left and right inferior lateral occipital cortices (iLOC) as primary EBA seeds (FSL Harvard–Oxford atlas). Both groups exhibited the expected widespread baseline EBA connectivity to visual and body-perception networks. However, when contrasting hands with cars (Hands > Cars) with the seed from the left iLOC only signers showed strong connectivity to other brain regions (bilateral superior parietal cortices and left middle frontal gyrus). The seed from the right iLOC revealed a similar functional connectivity pattern with two additional clusters in the left intraparietal sulcus and right middle frontal gyrus for deaf signers. Contrasting poses with cars using the left iLOC seed, we found greater connectivity for signers in the right EBA, left supramarginal gyrus and bilateral precuneus. With the seed from right iLOC, signers showed greater connectivity in the right EBA, left middle frontal gyrus, left middle temporal gyrus, left SMG, and bilateral precuneus. Direct between-group comparisons on FC for the hand or pose conditions using only the seed from the left or right iLOC, revealed highly specific patterns: Deaf signers consistently showed significant EBA coupling with bilateral superior temporal gyri for both hand and pose conditions, and left supermarginal gyrus (SMG), left inferior gyrus (IFG), right middle temporal gyrus (MTG), and right insula for the pose condition only. These results demonstrate that early exposure to ASL leads to stronger functional connectivity between visual body-selective cortex and brain regions known to be involved in the language network for ASL. The findings also provide strong neurobiological evidence of experience-dependent plasticity: when language is perceived or expressed through dynamic body movements rather than through the auditory–vocal channel, visual body-perception areas become tightly integrated with other brain regions that form the core language network. The results also underscore the flexibility of the human language network and its capacity to incorporate modality-specific visual cortices when linguistic input is visuospatial. Future work should examine whether the EBA–language coupling is impacted by age of acquisition and/or can predict individual differences in sign language proficiency.
Topic Areas: Signed Language and Gesture, Multisensory or Sensorimotor Integration