Presentation
Search Abstracts | Symposia | Slide Sessions | Poster Sessions | Lightning Talks
The neural correlates of metaphor: An fNIRS Study
There is a Poster PDF for this presentation, but you must be a current member or registered to attend SNL 2023 to view it. Please go to your Account Home page to register.
Poster A24 in Poster Session A, Tuesday, October 24, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Erin Meier1, Anna Schwartz1; 1Northeastern University
Metaphors are phrases frequently used in daily conversation in which two constructs are compared to highlight how one construct’s meaning overlaps with another (e.g., “Her smile was a cat’s purr”). The extent to which the left hemisphere (LH) versus the right (RH) hemisphere are necessary for metaphor processing is debated. Between-study inconsistencies in findings may stem from differences in stimulus familiarity and difficulty. Novel metaphor processing is more challenging than processing familiar metaphors, while metaphors are more challenging than literal phrases. Using functional Near-Infrared Spectroscopy (fNIRS) and a paradigm adapted from fMRI from Cardillo et al. (2012), we first tested the hypothesis that compared to literal sentences, metaphors would recruit several core LH language regions—including inferior frontal gyrus (IFG), middle temporal gyrus (MTG), inferior temporal gyrus (ITG), and supramarginal gyrus (SMG), and angular gyrus (AG)—their RH homologues, and regions within the multiple demand network not traditionally associated with language processing (bilateral dorsolateral prefrontal cortex [DLPFC]). We also hypothesized that novel metaphors would recruit bilateral IFG pars triangularis and posterior LMTG more than familiar metaphors. Twenty-eight healthy individuals (n=14 female; mean age=23.1±3.1 years) participated. First, during a familiarization task, participants were presented 50% of all stimuli and asked to make judgments on imageability, figurativeness, comprehensibility for each stimulus. The fNIRS task was split into two runs with three 25s-blocks/run of each of the following four conditions: 1) familiar metaphors (FAM/MET), 2) novel metaphors (NOV/MET), 3) familiar literal phrases (FAM/LIT), and 4) novel literal phrases (NOV/LIT). Data were acquired using two daisy-chained 8x8 NIRx NIRSport2 devices. The montage included 22 measurement channels/hemisphere and 8 short separation channels. Preprocessing in Homer3 (Huppert et al., 2009) included raw data to optical density (OD) transformation, motion detection and correction via splineSG, rejection of stimuli with uncorrected artifacts (t-range: -5–10sec), low-pass filtering at 0.5 Hz, conversion of OD to concentration, and estimation of the HRF (t-range: -2–25sec) via OLS-GLM for the contrasts of MET > LIT and NOV/MET > FAM/MET (p < 0.01). Image reconstruction was performed in AtlasViewer (Aasted et al., 2015). For MET>LIT, we found highly left-lateralized activity in most perisylvian language areas, including LIFG, pars opercularis, ventral precentral and postcentral gyri, LSMG, anterior LAG, mid and posterior LSTG, and mid LMTG as well as mid to posterior RMTG. For the contrast NOV/MET>FAM/MET, we found similar patterns of left lateralized activity as the previous contrast but overall weaker effects. In the RH, greater changes in oxyhemoglobin concentrations were noted in RIFG, pars opercularis for novel versus familiar metaphors. Our findings suggest that the right hemisphere and DLPFC do not play a significant role in metaphor processing in healthy, young adults, in contrast with some prior literature (Cardillo et al., 2012). However, metaphors required more core LH language regions than literal sentences, and novel metaphors required more LH resources than familiar metaphors, consistent with our hypotheses. Future directions include extending this research to neurologically healthy older individuals and clinical populations who struggle with metaphor processing (e.g., right hemisphere stroke survivors).
Topic Areas: Meaning: Lexical Semantics,