Abstract
Signed language is a natural language perceived through the eyes and produced in space with levels of linguistic organization that are found in spoken languages such as phonology, morphology, and syntax. The visuospatial processing demands that arise from using signed languages have been shown in studies to impact signers’ spatial cognition—something that is generally considered malleable across the lifespan. However, signed languages and its underlying brain sites, just like spoken languages, have been shown to be sensitive to age of language exposure (AoE)—time point in life where the human was exposed to a language. Here, we ask whether AoE to a signed language impacts neural activity related to spatial working memory (SWM). Using a spatial n-back task while participants were recorded with functional Near Infrared Spectroscopy (fNIRS) brain recording, we tested three groups of hearing, adult signers based on their age of exposure and proficiency in American Sign Language (ASL). As expected, we found that all three groups showed equal behavioral performance across all n-back conditions. However, only Native signers showed significantly greater brain activity in left dorsolateral prefrontal cortex and bilateral ventrolateral prefrontal cortex for specific n-back conditions when compared with Proficient and New signers. Taken together, these results show that early exposure to a signed language impacts the way the brain processes spatial information—a finding that raises the possibility that early exposure to a signed language may be used as a novel tool to improve spatial cognition in the general population.