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Functional neuroanatomy of sign language production: An Activation Likelihood Estimation meta-analysis
Poster Session D, Saturday, September 13, 5:00 - 6:30 pm, Field House
Lydia Wiernik1,2, Angela D. Friederici1, Karen Emmorey3, Patrick C. Trettenbrein1,2; 1Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2Experimental Sign Language Laboratory (SignLab), Department of German Philology, University of Göttingen, Göttingen, Germany, 3Laboratory for Language & Cognitive Neuroscience, School of Speech, Language and Hearing Sciences, San Diego State University, San Diego, CA, United States of America
Introduction: Sign languages are natural languages in the visual-kinesthetic modality (Kusters et al., 2020) which use the hands, body, facial expressions like eyebrow movement and eye gaze, mouthing, and mouth gestures as articulators (Hodge, 2020). Despite differences in the production channels, neuroimaging studies of sign production have identified similarities with the functional neuroanatomy underlying speech production (e.g., Emmorey et al., 2003, 2016, 2021; Kassubek et al., 2004; Buchsbaum et al., 2005; MacSweeney et al., 2008; Campbell et al. 2008; Hu et al., 2011; Okada et al., 2016). However, no prior work has provided a statistical synthesis of this available data on sign language production. Here, we fill this gap by reporting the results of the first Activation Likelihood Estimation (ALE) meta-analysis of the published neuroimaging literature on sign language production. Methods: We searched all major databases to identify relevant literature and included studies based on pre-defined criteria: (1) Participants were healthy deaf or healthy hearing users of any sign language; (2) the study focused on overt sign production and reported foci from relevant contrasts from the whole brain; and (3) imaging was performed using PET or fMRI. Individual contrasts in relevant papers were included in analysis if they involved sign language production in any capacity. The final sample comprised 14 studies with 168 participants and 553 foci. We first performed an ALE analysis (Eickhoff et al., 2012; Turkeltaub et al., 2012) with conservative thresholds (cFWE p < 0.05) which yielded only two significant clusters. Therefore, we conducted a second ALE analysis with more lenient thresholds (uncorrected cluster forming threshold p < 0.001) yielding 13 significant clusters. We then performed Jackknife analysis to ensure the observed clusters in either ALE analysis were not driven by a single study. Finally, to further characterize the functional nature of clusters surviving Jackknife analysis, we employed multi-analytic connectivity modeling (MACM) using the BrainMap database, which contains data only from studies with hearing non-signers. Results: Three clusters survived Jackknife analysis. These were located in the left inferior frontal gyrus (BA 45, 46, 47) extending into the left anterior insula (BA 13), left middle frontal gyrus (BA 6), and the medial and right cerebellum. Interestingly, the cerebellar cluster was limited to lobules IV and V, contrasting recent work on spoken language (Todorovic et al., 2024; Parker Jones et al., 2024). Our MACM analysis confirmed that all our identified clusters observed for sign language production are also primarily recruited for language processing in hearing non-signers with the exception of the cerebellar cluster which was primarily linked to action execution. Conclusion: Our findings provide support for the notion that core regions involved in language production are involved in the externalization of linguistic signals, regardless of the alternative language production channels between signed and spoken language. We also observe involvement of the cerebellum in sign production across studies, which has not previously been consistently reported. In sum, our work complements prior studies on (sign) language comprehension and production to provide a more refined, modality-independent understanding of language in the brain.
Topic Areas: Signed Language and Gesture, Language Production