Abstract
Neuroimaging studies suggest greater involvement of the left parietal lobe in sign language compared to speech production. This stronger activation might be linked to the specific demands of sign encoding and proprioceptive monitoring.In Experiment 1 we investigate hemispheric lateralization during sign and speech generation in hearing native users of English and British Sign Language (BSL). Participants exhibited stronger lateralization during BSL than English production. In Experiment 2 we investigated whether this increased lateralization index could be due exclusively to the higher motoric demands of sign production. Sign naïve participants performed a phonological fluency task in English and a non-sign repetition task. Participants were left lateralized in the phonological fluency task but there was no consistent pattern of lateralization for the non-sign repetition in these hearing non-signers.The current data demonstrate stronger left hemisphere lateralization for producing signs than speech, which was not primarily driven by motoric articulatory demands.
Highlights
The left hemisphere plays a critical role in language processing in the majority of the population (Hellige, 1993)
We investigated the role of movement during sign production further by comparing lateralization patterns during English phonological fluency and a non-sign repetition task in which hearing non-signers were asked to repeat non-signs
By examining language lateralization using functional transcranial Doppler sonography (fTCD) with a task other than the ‘gold standard’ phonological fluency task, we have shown that semantic fluency may be more appropriate for assessing language lateralization in signed languages
Summary
The left hemisphere plays a critical role in language processing in the majority of the population (Hellige, 1993). Lesion and neuroimaging studies have shown that signed languages appear to rely on a left lateralized network for both comprehension and production (Bellugi, Klima, & Poizner, 1988; Corina, 1999; Corina et al, 1999; Damasio, Bellugi, Damasio, Poizner, & Van Gilder, 1986; MacSweeney, Capek, Campbell, & Woll, 2008; MacSweeney, Waters, Brammer, Woll, & Goswami, 2008). In addition to analogous activation in the classical left perisylvian areas for sign and speech, previous neuroimaging studies have identified the left parietal lobe as having a greater role in signed than spoken language processing (for a review see Corina, Lawyer, & Cates, 2012; MacSweeney, Capek, et al, 2008; MacSweeney, Waters, et al, 2008). Studies of sign production in particular have highlighted an important role for the left parietal lobe (Braun, Guillemin, Hosey, & Varga, 2001; Corina, San Jose-Robertson, Guillemin, High, & Braun, 2003; Emmorey, Mehta, & Grabowski, 2007)
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