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Examining visual expertise with ASL fingerspelling: An N170 ERP study with deaf signers and hearing non-signers
Poster Session F, Friday, October 2, 2:45 - 4:45 pm, Wangari Maathai
This poster is part of the Sandbox Series.
Sofia E. Ortega1, Katherine J. Midgley2, Phillip J. Holcomb2, Karen Emmorey2; 1San Diego State University & University of California, San Diego, 2San Diego State University
Many deaf readers are fluent in both a signed language (e.g., American Sign Language) and a spoken language (e.g., English) or its written form. Sign languages blend aspects of both sign and print through fingerspelling, the use of handshapes to represent the surrounding orthographic system. In ASL, fingerspelling is produced by rapidly and fluidly stringing together handshapes that correspond to letters of the English alphabet. Importantly, ASL fingerspelling skills are a strong predictor of English reading skills in deaf signers throughout the lifespan. Although fingerspelling has been proposed as a gateway to literacy in deaf individuals, little is known about the neural mechanisms underlying fingerspelling perception. In the case of printed word perception, the N170 event-related potential (ERP) component is thought to reflect a process of category-specific visual expertise whereby visual word forms are mapped onto associated representations. This type of neural tuning is experience-dependent and only present for words after children learn how to read. Recent findings from an ERP study suggest that fingerspelled words generate right-lateralized N170 amplitudes in deaf signers that differ from the bilateral N170 response to print and ASL signs. However, hearing non-signers were not included as a control group to determine whether early and life-long experience with fingerspelling modulates the amplitude or laterality of the N170 effects. To address this question, the planned research will explore N170 expertise effects by collecting continuous EEG from 27 deaf ASL signers and 27 hearing non-signers while they view fingerspelled words and perform a go/no-go dot-detection task (press for an occasional dot that appears on the video near the sign model). Additionally, deaf signers will see a separate experimental list containing fingerspelled words, ASL signs, and printed words while they perform a go/no-go semantic categorization task (press to animals). Hearing non-signers will also perform a semantic categorization task, but for print stimuli only. Measures of phonological awareness skills will be collected for all participants. Fingerspelling skills will be measured in deaf participants. Mean amplitudes of ERPs will be measured from 120-240ms at two lateral posterior sites: T5, T6. Using ANOVAs, we will examine group differences (i.e., expertise effects) in N170 responses to fingerspelled words from the dot detection task. We hypothesize that deaf signers will exhibit larger N170 amplitudes to fingerspelled words than the hearing non-signers because they have undergone early neural tuning resulting in visual expertise for fingerspelled letters. Consistent with recent findings, we expect the N170 fingerspelling expertise effect to be stronger over the right hemisphere. Such a finding would suggest that early exposure to fingerspelling establishes right lateralized mechanisms that integrate visual-manual information with associated orthographic representations. As deaf signers learn to read, they may recruit these multi-modal neural systems and rely less on phonological routes. In line with this, we expect N170 responses to be bilateral in deaf readers and left-lateralized in hearing readers, consistent with prior literature. Lastly, we anticipate signs to generate bilateral N170 activity because previous findings indicate that early sign perception engages bilateral visual processing regions within occipital cortex.
Topic Areas: Signed Language and Gesture, Reading