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Brain regions critical for phonological processing in spoken production: Evidence from TMS

Poster Session B, Wednesday, September 30, 4:30 - 6:30 pm, Wangari Maathai

Lydia Z. Huang¹, Katie L. McMahon^2,3, Angélique Volfart⁴, Greig I. de Zubicaray¹; ¹School of Psychology and Counselling, Faculty of Health, Queensland University of Technology, ²School of Clinical Sciences, Faculty of Health, Queensland University of Technology, ³Herston Imaging Research Facility, Royal Brisbane & Women’s Hospital, ⁴University of Luxembourg

Neuroimaging studies in healthy participants have shown consistent engagement of the left posterior superior and middle temporal gyri (LpSTG/pMTG) during phonological processing in spoken production (e.g., de Zubicaray & McMahon, 2009). However, studies in lesion patients and patients receiving direct electrical stimulation have implicated the left supramarginal gyrus (LSMG) in phonological speech errors (e.g., Dell et al., 2013; Sarubbo et al., 2020). According to some production models, the LpSTG/pMTG and LSMG respectively process auditory and articulatory phonological representations (e.g., Dell et al., 2013; Gow, 2012). We plan to investigate whether these regions are critical for phonological processing by applying repetitive transcranial magnetic stimulation (rTMS) to them during picture naming. To target phonological processing, we will use a blocked cyclic naming paradigm and a context manipulation involving distributed segmental overlap in picture names that produces an interference effect in production latencies (e.g., pill, peg, log; Breining et al., 2016). We hypothesise that applying rTMS to both regions will disrupt performance compared to a control site (Vertex), increasing the magnitude of the interference effect, demonstrating their critical roles in output phonological processing. Twenty-four participants will attend 3 rTMS sessions (18 recruited to date), involving stimulation of the LpSTG/pMTG, LSMG, or Vertex. Stimulation will consist of 15 minutes of TMS pulses at 1 Hz using 90% of each participant’s resting motor threshold. Sessions will be conducted at least 7 days apart. Stimulation order of the regions will be counterbalanced across participants. The task comprises 36 pictures with monosyllabic names, with each 6 pictures repeatedly presented in homogenous and heterogenous blocks over 4 cycles. Words in each homogeneous block share phonemes in distributed word positions (i.e., onset, nucleus, and offset) whereas those in each heterogeneous block share minimally. The interference effect is demonstrated by significantly slower naming latencies in homogeneous versus heterogeneous blocks. This will be the first study to investigate the causal roles of the LpSTG/pMTG and LSMG in phonological processing during spoken word production in healthy speakers with rTMS. The findings will help clarify the roles of the two brain areas in production models. References Breining, B., Nozari, N., & Rapp, B. (2016). Does segmental overlap help or hurt? Evidence from blocked cyclic naming in spoken and written production. Psychonomic Bulletin & Review, 23, 500–506. https://doi.org/10.3758/s13423-015-0900-x de Zubicaray, G. I., & McMahon, K. L. (2009). Auditory context effects in picture naming investigated with event-related fMRI. Cognitive, Affective, & Behavioral Neuroscience, 9(3), 260–269. https://doi.org/10.3758/CABN.9.3.260 Dell, G. S., Schwartz, M. F., Nozari, N., Faseyitan, O., & Branch Coslett, H. (2013). Voxel-based lesion-parameter mapping: Identifying the neural correlates of a computational model of word production. Cognition, 128(3), 380–396. https://doi.org/10.1016/j.cognition.2013.05.007 Gow, D. W. Jr. (2012). The cortical organization of lexical knowledge: A dual lexicon model of spoken language processing. Brain and Language, 121(3), 273–288. https://doi.org/10.1016/j.bandl.2012.03.005 Sarubbo, S., Tate, M., De Benedictis, A., Merler, S., Moritz-Gasser, S., Herbet, G., & Duffau, H. (2020). Mapping critical cortical hubs and white matter pathways by direct electrical stimulation: An original functional atlas of the human brain. NeuroImage, 205, 116237. https://doi.org/10.1016/j.neuroimage.2019.116237

Topic Areas: Phonology, Language Production