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Does Early Access to Sign Language and Fingerspelling Influence Print-Tuning?
Poster Session C, Thursday, October 1, 10:45 am - 12:45 pm, Wangari Maathai
Ayden Kpormegbey1,2, Katherine Midgley1, Phillip Holcomb1, Karen Emmorey1; 1San Diego State University, 2University of California San Diego
The N170 component is a temporo-occipital negativity that is observed ~170 ms after a visual stimulus is presented and is argued to be a marker of neural tuning. Emmorey et al. (2017) found that deaf readers exhibited a more bilateral N170 response to words compared to skill-matched hearing readers who exhibited the expected left-lateralized N170. This finding is consistent with the phonological mapping hypothesis, which proposes that the N170 response shifts to the left hemisphere as children map letters to sounds, a process that is reduced for deaf readers. Further, reading skills were positively correlated with the amplitude of a right hemisphere N170 for deaf but not hearing readers, indicating that this neural response is not maladaptive for deaf readers. To determine if the difference in N170 laterality is influenced by the acquisition of a sign language or by learning to read without heavy reliance on sound, we investigated a population of early signers who likely rely on sound when learning to read. Hearing individuals born to deaf signing families are typically exposed to sign language from birth, and prior to learning to read they are also exposed to fingerspelling, a system that uses handshapes to represent letters. Early access to fingerspelling may change the N170 component to be more bilaterally distributed. We propose two possible hypotheses to explain the N170 laterality difference between deaf signers and hearing non-signers. The first follows the phonological mapping hypothesis that associates a left-lateralized N170 component with sound-letter mapping for hearing readers. If the phonological mapping is the primary driver of the left-lateralized N170 component, then hearing early signers should also show a left-lateralized N170 response to words. The second hypothesis proposes that early access to fingerspelling and/or sign language engages the right hemisphere and prevents a laterality shift to the left hemisphere in signers, perhaps because the right hemisphere (and a right-lateralized N170) is associated with body part recognition. If processing fingerspelling and sign language during childhood drives the bilateral N170 component, then hearing early signers should show a bilateral N170 response as found for deaf early signers. Following Emmorey et al. (2017), the current study used a familiarity judgement task where participants were asked to rate five-character words and ASCII symbol strings. Following a 500 ms fixation cross, each stimulus was presented for 300ms, followed by a 700ms blank screen, and then a response cue. Preliminary data on 9 hearing early signers indicate a left- lateralized N170 component, consistent with the pattern observed in hearing nonsigners. In addition, the hearing signers exhibit stronger phonological skills than the deaf signers. These findings suggest that hearing early signers leverage phonology while reading, similar to hearing nonsigners. Further data collection will allow us to determine which laterality of the N170 component is associated with phonological, reading, or spelling proficiency in hearing early signers, which will provide a better understanding of the underlying neural mechanisms behind print tuning and reading.
Topic Areas: Multilingualism, Signed Language and Gesture