Poster A57, Tuesday, August 20, 2019, 10:15 am – 12:00 pm, Restaurant Hall
Hemispheric lateralization during speech production is modulated by articulatory-phonological task demands
Heather Payne1, Eva Gutierrez-Sigut1,2, Mairéad MacSweeney1;1University College London, 2University of Valencia
Functional Transcranial Doppler sonography (fTCD) provides a measure of hemispheric lateralization by monitoring relative changes in blood flow in the left and right middle cerebral arteries during cognitive tasks (Aaslid et al., 1991, Deppe et al., 2004). As a portable and non-invasive method, it has been used to assess lateralization of language processing in typical and atypical populations across a range of language tasks (Knecht et al., 1998; 2001, Vingerhoets & Stroobant, 2002, Bishop et al., 2009, Badcock et al., 2012, Chilosi et al., 2012; Gutierrez-Sigut et al., 2015, 2016, Hodgson & Hudson, 2017, Payne et al., 2019). However, the factors underlying within- and between- subject variability in the extent of lateralization have not been established (Bishop, 2013; Woodhead et al., 2019). Here, we probe the sensitivity of fTCD by comparing the strength of lateralization during two well-matched speech production tasks. Drawing on psycholinguistic and neurobiological models of word production (e.g. Indefrey & Levelt, 2004, Hickock, 2012) and single word reading (Jobard et al., 2003), we predicted that an increasing reliance upon phonological planning and manipulation would result in greater activity from left posterior temporo-parietal to anterior perisylvian regions including left inferior frontal gyrus. These are core areas in the vascular territories of the MCA and should therefore impact on the extent of lateralization measured by fTCD. Participants (n = 19) were shown a series of single words and asked either to read each word aloud or generate a legal rhyming word. In line with our predictions, rhyme generation was more strongly left-lateralized than reading (t(18) = 2.70, p = .015, d = 0.6). While 14/19 participants showed no significant lateralization in either direction during single word reading, 13/19 showed significant left lateralization during rhyme production. This study highlights the contribution of task demands to individual variability in lateralization, as well as emphasizing that ‘language dominance’ is not a unitary concept.
Themes: Language Production, Methods
Method: Other