Slide Slam B19 Sandbox Series
The role of inferior frontal regions in phonological competition: Preliminary evidence from trial-level integration of eye-tracking with fMRI
Jennifer Mack1, Christine Reggio1; 1University of Massachusetts-Amherst
Purpose. This in-progress study uses concurrent eye-tracking/fMRI to investigate the role of the inferior frontal gyri (IFG) in phonological competition. Previous studies demonstrated increased activation in the bilateral IFG in the presence of an onset competitor picture (e.g., a cat for target cap) [1-2]. In addition, Broca’s aphasia, which typically involves damage to the left IFG, is associated with reduced onset competition and increased rhyme competition (e.g., fixations on a map for target cap) , suggesting that this region supports incremental word recognition processes that yield onset competition. This study has two goals: (1) to identify neural correlates of phonological competition through trial-level integration of eye-tracking and fMRI data; (2) to test the hypothesis that onset (vs. rhyme) competition is associated with greater IFG activation. Methods. Six young adults participated before data collection was paused due to Covid-19. Two participants were excluded due to motion or data collection problems. In each trial, participants saw four pictures, heard a word, and clicked on the target picture. There were two runs, each with 32 trials per condition (onset competitor, rhyme competitor, and filler), in an event-related design with jittered ITIs. For each onset and rhyme trial, we computed an eye-tracking measure of phonological competition (“ET”): the total fixation time on the competitor picture divided by the total fixation time on all pictures. fMRI analysis (SPM12) consisted of preprocessing and GLM specification with four conditions per run: onset trials, rhyme trials, filler trials, and excluded trials (due to incorrect responses or poor eye-tracking data). The phonological competition “ET” measure parametrically modulated the onset and rhyme trials. We analyzed data individually for the following contrasts: the overall effect of phonological competition (onset-ET + rhyme-ET) and pairwise comparison of onset vs. rhyme trials and onset-ET vs. rhyme-ET. The analysis was limited to the bilateral IFG (regions 44 and 45) using an ROI mask created with the SPM Anatomy Toolbox . We report significant clusters using a small-volume correction (peak-level FWE < 0.05). Results. Greater overall phonological competition was associated with increased activation within the IFG for three participants (bilateral in one; left in two). Onset > rhyme trials yielded activation in the bilateral IFG for one participant, whereas rhyme > onset trials did so in the left IFG for another. For two participants, very small (k<3) left IFG clusters were found for onset > rhyme ET. Conclusion and future directions. The association between IFG activation and overall phonological competition in three participants supports the validity of trial-level integration of eye-tracking with fMRI data. We found limited evidence that IFG activation is more strongly associated with onset than rhyme competition, as measured with eye-tracking. After data collection is completed in 2021, we plan to perform these analyses at the group level. Further, we will use IFG seed regions to test for differential connectivity patterns associated with onset vs. rhyme competition. References  Luthra, 2019. Lang. Cogn. Neurosci., 34(2).  Righi, 2010. J. Cogn. Neurosci., 22(2).  Mirman, 2011. Brain Lang., 117.  Eickhoff, 2005. Neuroimage, 25(4).